properties of malaysian fired clay bricks and their evaluation with international masonry...

PROPERTIES OF MALAYSIAN FIRED CLAY BRICKS AND THEIR

EVALUATION WITH INTERNATIONAL MASONRY SPECIFICATIONS

– A CASE STUDY

ZAINAB ARMAN ALI

UNIVERSITI TEKNOLOGI MALAYSIA

PROPERTIES OF MALAYSIAN FIRED CLAY BRICKS AND THEIR

EVALUATION WITH INTERNATIONAL MASONRY SPECIFICATIONS

– A CASE STUDY

ZAINAB BINTI ARMAN ALI

A thesis submitted in fulfilment of the

requirements for the award of the Degree of

Master of Engineering (Structure and Materials)

Faculty of Civil Engineering

Universiti Teknologi Malaysia

MAY 2005

iii

This thesis is dedicated to the people very dear to my heart:

my late parents, Arman Ali Hj Mohibullah and Zabedah Hamzah

my husband, Ayob Sharif

and my children…

Amlina, Aliza, Alira, Afandi Akmal, Alia Atika and Arfa Adlina

iv

ACKNOWLEDGEMENTS

The author wish to acknowledge the guidance, advice and assistance

given by her supervisor, Associate Professor Dr. Faridah Shafii and to thank her

for her encouragement and friendship, without which this thesis would not be

possible. The author is also greatly thankful to her for the limitless time she spent

in helping through with the writing of the thesis.

The author would like to acknowledge the support awarded by the

Government of Malaysia under the IRPA scheme in funding this research.

Appreciation is also due to Claybricks & Tiles Sdn Berhad for its contribution in

providing the bricks used in this research.

To the staff of concrete laboratory of the Civil Engineering Faculty of

UTM, thanks are due to the technicians, Ros, Amirul and Shahrul for helping

with works in the laboratory and sampling activity at the factory. Special thanks

are conferred to dear friends at the Faculty of Civil Engineering especially Zaiton

Haron who had given the author a lot of encouragement and motivation at the

beginning of the research. The author is also grateful to Dr. Zalina Daud of the

Science Faculty of UTM for her assistance in enlightening the mathematics of

statistics and Encik Yasin for his help in the Chemistry Laboratory.

Last but not least the author would like to thank all members of her family

especially the children who had given a hand on some computations and

computer skills.

v

ABSTRACT The research examined and assessed the properties of Malaysian fired clay

bricks to provide information for the development and revision of Malaysian Standard MS 76:1972. Some laboratory investigations on bricks were conducted in conjunction with the use of various masonry standards to evaluate the compressive strength, dimensional tolerances, water absorption, initial rate of suction, efflorescence, density and soluble salt content. The test methods were mostly based on MS 76:1972 and BS 3921:1985 and in some cases new testing approaches were adopted to assess new property requirements not catered in existing masonry specifications. The analysis on random samples indicated the acceptance of the use of a normal probability theory even for data with values of coefficient of variation close to 30%. In the case where the coefficient of variation exceeded 30 % the log-normal probability function applies. The statistical control charts traced data homogeneity for the population and data lying beyond the 5 % confidence limit, which were not accounted for in the analysis. The compressive strengths of facing bricks ranged from about 40 N/mm2 to 50 N/mm2 with lower values for common bricks, i.e. 30 N/mm2 to 40 N/mm2. These ranges of compressive strengths fall in the top range specified in Singapore Standard, SS 103:1974. The compressive strengths specified in ASTM were based on dry curing whilst British Standard, Singapore Standard and Malaysian Standard were tested in saturated conditions. Curing methods affect compressive strength with air curing giving higher values. Water absorption for the bricks under investigation range from 10 % to 12 % and therefore do not fit in the category of Engineering A or B of MS 76:1972 and BS 3921:1985, however satisfy the requirements for the categories of SW (severe weathering) bricks in ASTM. The dimensions satisfy the tolerances given in BS 3921:1985 except for the height. However, the dimensional tolerance fits the T1 category of the European Standard EN 771-1. The initial rate of suction for the bricks ranged from 1.4 to 2.0 kg/min/m2 indicating high suction property thus implying the necessity of wetting bricks before laying. Efflorescence does not seem to be a major problem hence these bricks could be satisfactorily used for facing construction purposes without resulting in salt deposition on the surfaces. The range of density (1760 to 1800 kg/m3) exhibited by the bricks satisfy the sound insulation requirements specified in the United Kingdom Building Regulations. In this research a method of predicting the compressive strength of bricks when laid in the different orientations was derived. This is a useful means of estimating the compressive strength of brick in practice where test are only conducted on the bed face. The research also highlighted a method of estimating the porosity of bricks for values of known water absorption.

vi

ABSTRAK

Penyelidikan ini mengkaji dan menilai sifat-sifat kejuruteraan bata tanah liat

bakar negara bagi membekalkan maklumat yang diperlukan untuk pembangunan Standard Malaysia MS 76:1972. Beberapa ujian makmal ke atas bata telah dijalankan selaras dengan penggunaan beberapa standard masonry untuk menganalisis kekuatan mampatan, toleransi pendimensian, penyerapan air, kadar resapan awal, ketumpatan, kesan peroi dan kandungan garam larut. Sebahagian besar ujian-ujian ini adalah berdasarkan kaedah MS 76:1972 dan BS 3921:1985 manakala pendekatan ujian semasa juga digunakan bagi menganalisis ciri-ciri baru yang tidak terkandung dalam spesifikasi sedia ada. Analisis sampel yang dipilih secara rawak menunjukkan penerimaan penggunaan teori kebarangkalian normal walaupun untuk data di mana nilai pekali perubahan menghampiri 30 %. Bagi kes dimana nilai pekali perubahan melebihi 30 %, fungsi kebarangkalian log-normal digunakan. Carta kawalan statistik digunakan untuk mengesan kehomogenan data dan data melampaui 5 % had keyakinan yang tidak diambil kira di dalam analisis. Kekuatan mampatan bata permukaan adalah antara 40 hingga 50 N/mm2 manakala bata biasa mempunyai nilai lebih rendah iaitu 30 hingga 40 N/mm2. Julat kekuatan mampatan ini tergulung dalam kategori tertinggi Standard Singapura, SS 103: 1974. Kekuatan mampatan dalam spesifikasi ASTM adalah berdasarkan bata diawet udara. Berbeza dengan Standard British, Singapura dan Malaysia, di mana bata di uji dalam keadaan tepu. Pengawetan udara memberikan nilai yang lebih tinggi. Penyerapan air adalah antara 10 hingga 12 %. Nilai ini tidak menepati keperluan MS 76:1972 dan BS 3921:1985 untuk kategori bata kejuruteraan A dan B. Walau bagaimanapun ia memenuhi syarat yang ditentukan dalam spesifikasi ASTM bagi bata jenis SW (terdedah pada kesan cuaca yang teruk). Dimensi bata dapat memenuhi keperluan toleransi pendimensian bagi standard BS 3921: 1985, kecuali ketinggiannya. Di bandingkan dengan Standard Eropah EN 771-1 pula, didapati ia menepati kategori T1. Kadar resapan awal bata ialah dari 1.4 hingga 2.0 kg/min/m2, menunjukkan ciri resapan yang tinggi, oleh itu bata perlu dibasahkan sebelum diikat. Bata tidak menghadapi masalah peroi, jadi ia boleh digunakan sebagai bata permukaan tanpa berlaku pemendapan garam di permukaannya. Julat ketumpatan bata ialah 1760 hingga 1800 kg/m3, sesuai bagi penggunaan dinding bangunan dengan nilai rintangan kebisingan memenuhi spesifikasi kanun bangunan di United Kingdom. Dalam penyelidikan ini kaedah untuk meramalkan kekuatan mampatan bata apabila disusun dengan orientasi yang berlainan telah dapat dihasilkan. Kaedah ini berguna bagi menganggarkan kekuatan mampatan bata secara praktikal dimana ujian mampatan hanya dilakukankan di permukaan atas bata. Kajian ini juga menerangkan kaedah menganggarkan keliangan bata daripada nilai penyerapan airnya.

vii

TABLE OF CONTENTS

CHAPTER TITLE PAGE

TITLE PAGE i

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES xiii

LIST OF FIGURES xviii

LIST OF SYMBOLS AND ABBREVIATIONS xxi

LIST OF APPENDICES xxii

1 INTRODUCTION 1

1.1 History and Development of Masonry 1

1.2 Manufacturing of Clay Bricks 2

1.3 Construction Requirements for Masonry and

the Needs for Specification

3

viii

1.4 Masonry Standardisation and International

Development

4

1.5 Defining the Contents for Standard

Specifications

5

1.6 Research Problem 6

1.7 Aim and Objectives of the Research 8

1.8 Scope of Work 9

1.9 Layout of Thesis 10

2 LITERATURE REVIEW 12

2.1 Introduction 12

2.2 Compressive Strength 12

2.2.1 Strengths Variability 12

2.2.2 Brick Strength and Masonry Strength 13

2.2.3 Effects of Brick Type and Geometry 15

2.2.4 Effects of Test Methods and

Measurements

15

2.3 Dimensional Tolerance 17

2.4 Water absorption 19

2.5 Initial Rate of Suction 22

2.6 Soluble Salt Content and Efflorescence

Effects

24

2.7 Density 24

2.8 Brick Specifications in International

Standards

26

2.8.1 Compressive Strengths 26

2.8.2 Water Absorption 28

ix

2.8.3 Initial Rate of Suction (IRS) 29

2.8.4 Dimensional Tolerance 30

2.8.5 Efflorescence 33

2.8.6 Soluble Salt Content 35

2.9 Test Methods and Measurements in

International Standards

37

2.9.1 Methods of Sampling for Tests in

International Standards

37

2.9.2 Compressive Strengths 38


2.9.4 Initial Rate of Suction 41


2.9.6 Efflorescence 42

2.10 Conclusions 49

3 LABORATORY TESTS ON PHYSICAL

PROPERTIES OF BRICKS

54

3.1 Introduction 54

3.2 Sampling of Bricks 54

3.3 Testing Programme 55


3.5 Density 61


3.7 Water Absorption (5-hours boiling test) 66


3.9 Soluble Salt Content 72

3.10 Efflorescence 79

x

4 STATISTICAL ANALYSIS OF TEST SPECIMENS 81

4.1 Introduction 81

4.2 General Approach for Analysing Sample 81

4.2.1 Description of Data 82

4.2.2 Histograms and Normal Distribution

Curve

84

4.2.3 Log-normal Distribution Curve 86

4.2.4 Derivation of Population Estimates 87

4.2.5 Hypothesis Testing 89

4.2.5.1 Analysis of Variance

(ANOVA)

89

4.2.5.2 Control Charts 90

4.3 Application of Statistical Methods for

Samples Under Investigation

93

4.3.1 Description and Presentation of

Sample Data

96

4.3.2 Test for Data Homogeneity 103

4.3.3 Determination of Sample Variance

Using the ANOVA

105

4.3.4 Estimates of Population Mean 107

4.4 Conclusions 107

5 RESULTS AND DISCUSSIONS 110

5.1 Introduction 110



xi

5.3.1 Overall Dimension of 24 Bricks 125

5.3.2 Dimension of Individual Brick for

Length, Width and Height

125

5.4 Water Absorption 135


5.6 Density 142

5.7 Efflorescence 146

5.8 Soluble Salt Content 146

6 APPLICATION OF RESEARCH FINDINGS 148

6.1 Relationship of Aspect Ratio to Compressive

Strength

148

6.2 Relationship of Water Absorption to Porosity

and Compressive Strength

151

7 CONCLUSIONS AND RECOMMENDATIONS

FOR FURTHER WORK

154

7.1 Conclusions 154

7.2 General Conclusions 154

7.3 Detailed Conclusions 155

7.3.1 Compressive Strength 155



7.3.4 Initial Rate of Suction 157

7.3.5 Soluble Salt Content 156

7.3.6 Density 158

xii

7.4 Recommendations for Further Work 158

REFERENCES 161

APPENDICES 165

xiii

LIST OF TABLES

TABLE TITLE PAGE

2.1

Compressive strengths of bricks tested in different

orientations (Hendry, 1997)

16

2.2 Aspect Ratio Factor (Ka) 17

2.3 Limits of durability indices (Surej et al., 1998) 21

2.4 Characteristic flexural strengths and levels of water

absorption (BS 5628 Pt. 1, 1985)

21

2.5 Typical sound insulation values of masonry walls

(Curtin et al., 1995)

25

2.6 Classification of bricks by compressive strength and

water absorption (BS 3921:1985)

26

2.7 Physical requirements for building bricks (ASTM C

62-89a, 1990)

27

2.8 Characteristic compressive strength in accordance to

Australian Standard (AS 1225:1984)

27

2.9 Dimensional tolerance based on measurement of 24

bricks and coordinating and work size in accordance to

British Standard (BS 3921:1985)

30

2.10 Dimensional tolerance in accordance to Australian

Standard (AS 1225 – 1984)

31

2.11 Dimensional tolerance of facing bricks in accordance

to ASTM C 216-90a (1990)

32

2.12 Dimensional tolerance for mean value of work size in

accordance to European Standard (prEN 771-1, 2000)

33

xiv

2.13 Dimensional tolerance for range of work size in

accordance to European Standard (prEN 771-1)

33

2.14 Classification of bricks in accordance to dimensional

deviation limits in Singapore Standard (SS103: 1974)

33

2.15 Levels of efflorescence in British Standard (BS

3921:1985)

34

2.16 Levels of efflorescence for the Australian Standard

(AS 1225 – 1984)

35

2.17 Levels of efflorescence in Singapore Standard

(SS103: 1974)

35

2.18 Maximum salt content for the low category (L) in

accordance to British Standard (BS 3921:1985)

36

2.19 Soluble salt content categories in accordance to

European Standard (prEN 771-1)

37

2.20 Sample size for tests in international standards 38

2.21 Comparison of water absorption from 5-hr boiling and

the 24-hr cold immersion tests using whole brick and

brick lumps (Khalaf and DeVenny, 2002)

40

2.22 Test methods and measurements for compressive

strength in international standards

43

2.23 Test methods and measurements for water absorption

in international standards

44

2.24 Test methods and measurements for initial rate of

suction in international standards

45

2.25 Test methods and measurements for dimensional

tolerance in international standards

46

2.26 Test methods and measurement for efflorescence in

international standards

48

3.1 Testing programme 56

3.2 Overall dimensions of 24 bricks 58

3.3 Individual brick measurement of length, width, and

height for all batches.

59

3.4 Density of bricks for Batch 1 62

xv

3.5 Initial rate of suction in samples for Batch 1 65

3.6 Water absorption of bricks for Batch 1 67

3.7 Compressive strength of common bricks tested on bed

face

70

3.8 Compressive strength of facing bricks tested on bed

face

71

3.9 Compressive strength of facing bricks tested on the

stretcher face

72

3.10 Compressive strength of facing bricks tested on the

header face.

72

3.11 Percentage of sulphate content in samples for all

batches

73

3.12 Standard calibration for calcium 75

3.13 Percentage of calcium in samples for all batches 76

3.14 Standard calibration for sodium and potassium 76

3.15 Percentage of potassium in samples for all batches 77

3.16 Percentage of sodium in samples for all batches 78

3.17 Standard calibration for magnesium 78

3.18 Percentage of magnesium in samples for all batches 79

4.1 Components of variance from ANOVA 90

4.2 Water absorption of specimens in each sample for

facing brick

98

4.3 Frequency distribution of data for facing bricks 99

4.4 Normal and log-normal curve fit for water absorption 100

4.5 Normal and log-normal curve fit for compressive

strengths of common bricks

101

4.6 Comparisons of 33 percentile values from normal and

log-normal curve for compressive strength of common

brick

103

4.7 Probability that x will not be exceeded 103

4.8 Sample means and ranges for water absorption 104

xvi

4.9 Control limits for means and ranges for water

absorption

104

4.10 Samples accounted for in the estimate of population

mean for water absorption

106

4.11 ANOVA and components of variance for water

absorption

106

5.1 Compressive strength of specimens in each sample for

facing bricks tested on bed face

111


facing bricks tested on stretcher face

112


facing bricks tested on header face

112

5.4 Normal curve fit for compressive strength of facing

bricks tested on bed and stretcher face

113

5.5 Log-normal curve fit for compressive strength of

facing brick tested on header face

114

5.6 ANOVA and variance components for compressive

strengths of facing bricks tested on bed, stretcher and

header faces

117

5.7 Compressive strength of facing brick when tested on

bed face as computed from net areas

120

5.8 Compressive strength of facing and common bricks

and standard requirements

122


common bricks

123

5.10 Overall measurement of length, width and height of 24

bricks and individual brick dimensional deviations

from work size

126

5.11 Dimensional deviations of brick from work size and

comparisons with values of dimensional tolerance for

BS 3921:1985 and prEN 771-1

128

xvii

5.12 Individual brick dimensions for length, width and

height in all samples

130

5.13 Mean dimensions of individual length, width and

height of brick compared with British Standard (BS

3921:1985)

135

5.14 Water absorption of specimens in each sample for

facing bricks

135

5.15 Comparison of water absorption with limits specified

by British Standard and ASTM

137

5.16 Relationship between characteristic flexural strengths

and levels of water absorption (BS 5628 Pt. 1)

138

5.17 Computed values for initial rate of suction of

specimens for facing bricks based on gross area of

immersion

139

5.18 Computed values for initial rate of suction of

specimens of facing bricks based on net area of

immersion

142

5.19 Density of specimens in each sample for facing bricks

143

5.20 Density of bricks for walls and walls with plaster finish

(Building regulations of the UK)

145

5.21 Typical sound insulation values of masonry walls

(Curtin et al., 1995)

145

5.22 Percentage of soluble salts in samples from all batches 146

6.1 Relationship between bricks compressive strength,

water absorption and porosity (Khalaf, 2002)

152

xviii

LIST OF FIGURES

FIGURES TITLE PAGE

2.1 Mean compressive strength of walls against brick

strength for 102mm thick brickwork in various mortars

14

2.2 Expansion of kiln-fresh bricks due to absorption of

moisture from atmosphere

19

2.3 Relationship of flexural strength of brickwork with

water absorption of bricks in plane of failure (a) and (c)

parallel to bed joints and (b) and (d) perpendicular to

bed joints (Morton, 1986)

22

3.1 Sequence of testing 56

3.2 Overall Measurement of (a) length, (b) width

and (c) height for 24 bricks

60

3.3 Apparatus for the measurement of density 63

3.4 Apparatus for measuring the initial rate of suction 65

3.5 Apparatus for water absorption test 66

3.6 Compressive machine -Tonipact 3000 69

3.7 a Bricks tested on bed face 69

3.7 b Bricks tested on stretcher face 69

3.7 c Bricks tested on header face 70

3.8 A schematic diagram of an atomic absorption

spectrometer (Hammer, 1996)

74

3.9 Calibration curve for detection of calcium 75

3.10 Calibration curve for detection of sodium and

potassium

77

3.11 Calibration curve for detection of magnesium 78

xix

3.12 Efflorescence test 80

4.1 Mean, median and mode in a distribution skewed to the

right.

84

4.2 Areas under normal probability curve 88

4.3 T-distribution curves for various values of n (Chatfield,

1978)

89

4.4 Control charts for sample means and ranges (Neville,

1985)

93

4.5 Process of statistical analysis 95

4.6 Histogram, normal curve and log-normal curve, for

water absorption of bricks

99

4.7 Histogram, normal and log-normal curve for

compressive strength of common bricks (c.v.

approaching 30%)

103

4.8 Control chart for means values of water absorption

105

4.9 Control chart for ranges of water absorption. 105

5.1 Histogram, normal and log-normal curve for

compressive strength of facing bricks tested on (a) bed

face (b) stretcher face (c) header face

115

5.2 Control charts of mean values and ranges for

compressive strengths tested on (a) bed face (b)

stretcher face (c) header face

116

5.3 Relationship between compressive strength and h/t

ratio of bricks

119

5.4 Relationship between the computed compressive

strength (based on net loaded area of bed face) to h/t

ratio

121

5.5 Histogram and normal curve for compressive strength

of common bricks

123

5.6 Control charts of mean values and ranges of samples

for compressive strength of common bricks

125

5.7 Comparison of overall dimensions of (a) length (b) 127

xx

width and (c) height with allowable range of British

and Singapore Standard

5.8 Histogram and normal curve for individual dimensions

of length, width and height of bricks

133

5.9 Control charts for mean values and ranges of samples

for (a) length (b) width and (c) height of bricks

134

5.10 The histogram and the normal curve fit for water

absorption of bricks

136

5.11 Control chart of mean values and ranges of samples

for water absorption of bricks

137

5.12 Histogram and normal curve fit for IRS based on gross

area of immersion

140

5.13 Control charts for means and ranges for IRS based on

gross area of immersion

140

5.14 Histogram and normal curve fit for density of bricks 144

5.15 Control charts for mean values and ranges of samples

for density of bricks

144

6.1 Relationship between compressive strength and h/t

ratio of bricks

149

6.2 Orientations of bricks in a brick laying (a) header face

(b) bed face and (c) stretcher face.

149

6.3 Relationship of water absorption with porosity from

Table 6.1

152

6.4 Relationship of porosity with compressive strength

from Table 6.1

152

xxi

LIST OF SYMBOLS AND ABBREVIATIONS

ANOVA - analysis of variance

Mpa - Megapascals

AS - Australian Standard

ASTM - American Standard of Testing Materials

BS - British Standard

c.v. - Coefficient of variation

df - Degree of Freedom

EN - European standard

MS - Malaysian Standard

MS - Mean of Squares

n - Sample size

N.H. - Null Hypothesis

NZS - New Zealand Standard

R - Range

s - Sample standard deviation

SS - Sum of squares

Std. dev. - Standard deviation

Var - Variance

ν - Coefficient of variation

x - Mean of sample means

µ - Population mean

σ - Population standard deviation 2s - Sample variance

x - Sample mean

xxii

LIST OF APPENDICES

APPENDIX TITLE PAGE

A1. Results of Tests Specimens for Dimensional 166

Tolerance of Individual Bricks

A2. Results of Test Specimens for Density of Bricks 170

A3. Results of Tests Specimens for Initial Rate 175

of Suction of Bricks

A4. Results of Tests Specimens for Water Absorption 183

of bricks

A5. Results of Tests Specimens for Compressive 188

Strength of Bricks

B. Statistical Tables 200

CHAPTER 1

INTRODUCTION

1.1 History and Development of Masonry

The history of civilisation is synonymous to the history of masonry. Man’s

first civilisation, which started about 6000 years ago, was evident by the remains of

the Mesopotamians masonry heritage. During those days masonry buildings were

constructed from any available material at hand. The Mesopotamians used bricks,

made from alluvial deposits of the nearby River Euphrates and Tigris to build their

cities beside these two rivers. Where civilisation existed in the vicinity of mountains

or rocky outcrops, stone was used. The Egyptians pyramids that existed along the

rocky borders of the Nile valley were examples of such stone masonry. In the

Eastern civilisation remains of historical masonry is the reputed Great Wall of

China, which is considered as one of the seven construction wonders in the world.

The materials used in the construction varied from tamped earth between timbers

and adobe i.e. sun-dried bricks to local stones and kiln-fired bricks. The part of the

wall that remains until today is mainly those made of bricks and granite.

The early forms of masonry application in Malaysia dated back about 350

years ago with the construction of the Stadthuys in Malacca, built by the Dutch in

1650. A more modern form of masonry construction was initiated by the British who

colonised the then Malayan Peninsula. Brickwork buildings were at that time built

specially for government offices, quarters and residential. The administrative block,

2

Sultan Abdul Samad building built in 1894 and given a face-lift during the Fourth

Malaysian Plan (1981 – 1985) is an example of a masonry heritage, which stands as

a remarkable landmark of Kuala Lumpur.

In its early forms masonry structures were built without any structural

calculations. Units of masonry consisting of stones or bricks were either stacked dry

or bonded with any adhesive material to form structures and self weight being used

to stabilise the construction. The Great Wall of China for example, stood at 6.5

meters wide at the base and 5.8 meters at the top, constructed at this massive scale

mainly for stability.

With the advancement of engineering technologies and manufacturing the

development of masonry units and their applications have extended beyond the

conventional approaches and processes leading to a more efficient design and

economy. Situations where considerable lateral forces have to be resisted, the low

tensile strength of bricks could be overcome by using reinforced masonry.

Construction where greater span lengths is desired, post tensioned bricks are used,

making it possible for bricks to be used in large single cell buildings.

1.2 Manufacturing of Clay Bricks

Clay brick is the most extensively used type of masonry units throughout the

world. Its widespread use is mainly due to the availability of clay and shale in most

countries. Its durability and aesthetics appeal also contribute to its extensive

application in both load bearing and non-load bearing structures.

Manufacturing techniques for the production of clay bricks have changed

from the initially hand moulded processes to modern mechanisation. At present

bricks are formed either by the process of extrusion, moulding or dry pressing.

These advance techniques of manufacturing allow greater flexibility in its design;

with a more efficient and varied burning process a wide range of products can be

manufactured. Longer burning processes also tend to produce denser units thus

3

allowing its use for load bearing purposes. Other variations including appearance,

colours, textures, sizes and physical properties could be designed accordingly to the

type of bricks to be produced and its application.

1.3 Construction Requirements for Masonry and the Needs for Specification

Due to the varying manufacturing process and the raw materials, bricks

produced could have a wide range of variability in its appearance and physical

properties making brick a versatile building unit in construction. Bricks are of great

importance for load bearing walls in low and medium rise buildings and for non-

load bearing walls as cladding for buildings. It serves several functions including

structure, fire protection, thermal and sound insulation, weather protection and

subdivision of space.

The several functions of bricks and the availability of a variety of bricks that

are able to serve the different construction requirements therefore require an

efficient and consistent guideline in achieving a safe, efficient and economical

design. This is often dictated by specifications and standards.

Load bearing brickworks, besides functioning as subdivision of space should

also have the load carrying capacity, necessary thermal and acoustics insulation as

well as fire and weather protection. Consequently, bricks in load bearing

applications should have adequate strength so that it could safely carry the loads

imposed by the structure and be able to meet the other physical requirements

specified in standards. On the other hand, non-load bearing brickworks are non-

structural, which are designed not to carry load and therefore consideration for

strength is of less importance compared to the requirements needed in load-bearing

masonry.

A damp-proof-course in brick walls at ground floor level prevent moisture

from the ground rising through the bricks and mortar and causing dampness in the

lower parts of the ground floor walls. For this reason bricks used as damp-proof-

4

course must be sufficiently impermeable and this could be ascertain through its

water absorption property.

Facial bricks are mostly produced as quality bricks with high compressive

strength and low water absorption as they can be efficiently applied as structural

bricks with aesthetics quality for use in external walls. These bricks should also

possess other physical requirements essential in good brickwork practices.

1.4 Masonry Standardisation and International Developments

The earliest standard was for weights and measures, which could be traced

back to the ancient civilisation of Babylon and early Egypt (IEEE, 2001). However,

the importance of standardisation was only fully realised until during the industrial

revolution of early nineteenth century.

As for masonry, standards had evolved through research discoveries and the

experience acquired over the years in the use of masonry. Each masonry standard is

different and unique for any country as it incorporates the national requirements. As

such the brick specifications for Australia, America, Britain differs. However, the

basic approach may be similar, to some extent. These standards were developed

more than several decades ago and used the prescriptive approach.

The trend towards globalisation requires harmonisation of standards and this

is evident with the European Standard (EN), which was established to encourage

trade between the European member states and the EN 771 became the new standard

thus setting new specifications of masonry units for Europe.

5

1.5 Defining the Contents for Standard Specifications

The international masonry standards define specifications by consideration

of the parameters described in the foregoing paragraph.

With respect to the mechanical properties of bricks, the most important is

compressive strength, which as well as being direct importance to the strength of a

wall, serves as a general index to the characteristics of the bricks. It is measured by

a standardised test, the results rely to a certain degree on the standard procedures

and conditions for testing prescribed in standards.

Bricks vary in their dimensions due to the variable shrinkage occurring

during and after manufacturing. This dimensional variability should be a minimum

in facing brickwork to ensure even joints for an aesthetically pleasant wall.

Water absorption of brick, which indicates bricks permeability, is dependent

on its porosity. Porous bricks will allow water to penetrate a wall more easily thus

contributing to problems of water seepage in masonry walls. This is an important

factor to be considered in masonry materials especially for tropical regions where

there is abundance of rain. In temperate countries, water absorption property of a

brick is used in standards in defining bricks durability in terms of its resistance to

freezing and thawing.

The initial rate of suction, which is the amount of water sucks by the brick

from mortar during laying, affects the bond between bricks and mortar in a

brickwork and is a required parameter in design of flexural walls. Optimum bond

strength could be achieved by ensuring the initial rate of suction is within the

specified limits in standards.

The other property, which is known to affect the appearance of a wall and

therefore critical in facing bricks is the effects of efflorescence. The whitish salts

deposits that appear on bricks surfaces are called efflorescence. Efflorescence is

caused by the presence of soluble salt in the bricks and water as the carrier, which

transport the salts to bricks surfaces.

6

The content of detrimental soluble salts in bricks also affects the durability of

brickwork. For example, if the amount of water-soluble sulphate exceeds the

allowable, sulphate attack will occur which will cause the disintegration of

brickwork and thus affecting its durability.

The various standards adopt different methods of measurement for

evaluating the properties of bricks. Limits may be specified to provide guidelines in

achieving satisfactory results of the final construction.

The Malaysian standard MS 76:1972 was a mere adoption of BS 3921,

excluding certain properties not relevant to Malaysian requirements, and therefore

limiting to a number of main properties only. With the advent of highly technical

manufacturing techniques and subsequently the presence of new range materials,

materials may have to be tested for additional physical and chemical properties, to

ensure its best performance after laid on construction site.

An improvement of Malaysian Standard is essential to cater with current

technical requirements and ensuring effectiveness of masonry applications. This

entailed investigations on brick properties before any recommendations could be

made on the materials and limits set to achieve satisfactory results in construction.

The research examine the various masonry specifications including

Malaysian Standard in an attempt to establish a better understanding of the various

standards and in deriving recommendations for Malaysian applications relating to

new technical requirements.

1.6 Research Problem

The development of the existing Malaysian standard MS 76:1972

(Specification for bricks and blocks of fired brickearth, clay or shale) were based on

BS 3921:Part 2:1969 (Specification for Bricks and blocks of fired brick-earth, clay

or shale). The British Standard had been revised twice, the latter versions being BS

7

3921:1974 and the existing BS 3921:1985. The revisions incorporate significant

details pertaining to material requirements and construction practices. Some of the

significant changes in existing British Standard BS 3921:1985 (British standard

specification for clay bricks) include bricks classifications, designations for

durability and new requirements on physical properties and revision of testing

methods.

The shift of British standard to European standard and eventual withdrawal

of the British Standard, therefore requires the Malaysian Standard to be revised

accordingly to suit to current market products and requirements for masonry

applications. Subsequently a research is necessary to study the various international

masonry specifications in providing a detailed understanding of the specifications

requirements, before recommendations be made to improve the existing brick

specification for Malaysia. These efforts will also facilitate the development of a

national standard capable of complying with standard global requirements.

In producing a national brick specification, data on local brick performance

are required to guide and support the new set of recommendations proposed for the

new standard.

The Malaysian Standard MS 76:1972 requires some essential amendments to

its specification to cater for present masonry application. For example, the existing

specification does not require any limit of salt content for ordinary quality facing

and common bricks, which are meant for external applications. Limits of soluble salt

content in bricks are essential as a preventive measures for salt deposition and

detrimental chemical reaction, which could damage the appearance of facial

brickwork construction. Investigation on the initial rate of suction property for

Malaysian bricks is crucial as this property, which is at present not included in the

specification, is an important criterion in structural brickwork design and

calculations.

The supplementation of data relating to local bricks performance is essential

to guide and support the new recommendations proposed for the improved

standard mentioned above.

8

1.7 Aim and Objectives of the Research

The aim of the research is to establish a detailed understanding of brick

properties through some laboratories investigations in conjunction with use of

various masonry standards to assess the material performance. The results of these

work supplemented with statistical studies and reviews of past research provides a

useful guidance to brick properties for local production. These work will also

provide data pertaining to current production of bricks which may be considered

significant to any revision or amendment made to the existing Malaysian Standard

for masonry MS 76:1972, currently under revision.

The objectives of the research are:

(i) To conduct an experimental investigation on compressive strength,

dimensional tolerances, density, initial rate of suction, water

absorption, efflorescence and soluble salt content of facing bricks.

(ii) To examine the compressive strength of common bricks.

(iii) To examine the compressive strengths of bricks tested in various

orientations as recommended by Australian/New Zealand and

European standard. Thus establish the relationship between the aspect

ratio (h/t) and compressive strength of bricks.

(iv) To study the density of bricks and its relation to acoustics properties

of masonry.

(v) To examine the statistics of locally manufactured bricks and the

respective control charts representing the population of bricks under

study.

(vi) To establish the relationship of water absorption, porosity and

compressive strength of bricks and to predict compressive strength

from known values of water absorption and porosity.

9

The studies were conducted through laboratory investigations of local bricks

and literatures establishing the state-of-the art of previous works and references to

international specification of masonry.

1.8 Scope of Work

The research is a case study, which dealt with the investigation of fired clay

facing and common bricks from a local manufacturer. The bricks were tested under

laboratory conditions as specified by the respective standards. The brick properties

examined were confined to studies on compressive strength, dimensional tolerance,

density, initial rate of suction, water absorption, efflorescence and soluble salt

content. Majority of the tests were based on the Malaysian Standard MS 76:Part 2

1972, which is basically an adoption of British Standard, BS 3921:1969. Since then

the British Standard for masonry has been revised several times to accommodate

changes for current needs.

Other standards used in the study were ASTM (American society for testing

and material), Australian/New Zealand standard, Singapore standard and European

standard. These standards formed the major references for comparisons of the

applications and methods of testing and determining the bricks properties

investigated in this programme. They form the major references for discussions in

this thesis.

Studies on bricks density are new to masonry and this was included in this

research in aligning with the new recommendations specified by the European

Standard.

The outcomes of the laboratory investigations were based on a local brick

manufacturer and therefore the results are inconclusive to suggest a representation of

the national population, however provides some guides to the properties of

Malaysian clay bricks.

10

1.9 Layout of Thesis

Chapter II describes the significance of physical and chemical properties of

bricks and its effects upon masonry behaviour. A review was conducted to examine

the various international masonry specifications, the recommended methods of

testing and measurements and comparisons between them. A considerable amount of

attention was given to the studies on masonry specifications by Malaysian Standard,

British Standard, and the Eurocode. Comparisons were also made by referring to

Australian/New Zealand Standard and ASTM. The limitations and advantages of the

various standards were highlighted and these form the basis of knowledge for the

work carried out in this thesis and where possible recommended for future standard

development.

Chapter III describes the laboratory works to identify the physical and

chemical properties of local clay bricks in providing data for Malaysian bricks. The

compressive strength, density, dimensions, water absorption, initial rate of suction,

efflorescence and salt content were investigated mainly using British Standard and

in specific cases other standards were also used. The British Standard is regarded as

the main reference used in this research as it is used widely in practice in Malaysia.

Chapter IV presents the statistical analysis of bricks properties investigated

in Chapter III. The descriptive statistics of data were computed and the graphical

distribution of data shown by histograms and normal curves. The application of

control charts was presented for testing data homogeneity. The analysis of variance,

ANOVA was used to derive the components of variances in samples, which in turn

will be used to calculate the bricks population mean.

Chapter V presents the experimental and statistical results for the bricks

properties investigated in the programme. The results for every parameter were

discussed and compared to previous research works and specification requirements

set by existing international standards.

11

Chapter VI presents a method of predicting compressive strength and

porosity properties of bricks based on the findings of work carried out in this thesis.

Chapter VII presents the conclusions of the works and recommendations for

future studies.

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

The properties of bricks affect the appearance and the quality of masonry

construction. Therefore, emphasis has been given by codes and standards to specify

the properties of units and component materials, in order to achieve the designated

durability, quality and strength.

This chapter presents works conducted on bricks for specifications

development and standardisations. Evaluation of bricks made on compressive

strengths, absorption properties, initial rate of suction, dimensional deviations,

efflorescence effects, soluble salt content and density i.e. the parameters contributing

to specification development.

2.2 Compressive Strength

2.2.1 Strengths Variability

The compressive strengths of bricks vary considerably with the material used

in manufacturing and the duration and degree of burning. Bricks compressive

13

strengths can be defined into three levels i.e. the high strength engineering bricks

with compressive strength ranging from 55 to 69 N/mm2, the medium strength

bricks range from 27 to 48 N/mm2 and the low strength brick range from

approximately 14 to 25 N/mm2 (Lenczner, 1972). Due to these considerable

variations, strengths of bricks are classified accordingly to its application in

construction. Bricks with compressive strengths of approximately 5 N/mm2 are

sufficient for the construction of low-rise buildings like dwelling houses

(Hendry et al., 1981). For high-rise structures, engineering bricks and those of high

compressive strengths should be used (Hendry, 2001).

The compressive strengths of bricks were associated with materials and

manufacturing features as highlighted by Grimm (1975). Additionally, the

compressive strength can be generally higher for the following cases:

• Units made of shale by the stiff mud process

• Burned at high temperatures

• Cored less than 35% of its gross area with no sharp re-entrant corners

• Units with small heights

2.2.2 Brick Strength and Masonry Strength

Compressive strength of a brick is important as an indicator of masonry

strength and as a result, brick strength has become an important requirement in

brickwork design. A considerable amount of past research and studies on masonry

(Hendry, 1990, Lenczner, 1972, Sahlin, 1971,) indicated that stronger bricks

contribute to greater brickwork strength.

Brickwork is strongest in compression and research shows that the

compressive behaviour of brickwork depends on the strength of brick and mortar.

However there is no suggestion of a direct relationship between the individual

component strength and the resultant masonry strength. The complex nature of

14

analysis for masonry (composite material) contributes to the difficulties in

establishing such relationship.

Some existing work based on the analysis of experimental data conducted on

102.5 mm and 215 mm thick walls (Hendry and Malek, 1990) showed that the

compressive strength of walls (f) could be estimated by the following equations:

For wall thickness of 102.5 mm 0.2080.5311.242 b mf f f= …(2.1)

For wall thickness of 215.0 mm 0.778 0.2340.334 b mf f f= …(2.2)

Where,

fb and fm are the brick and mortar compressive strengths respectively.

Equations 2.1 and 2.2 were represented graphically as shown in Figure 2.1

(Hendry, 1990) and has been used as a basis for estimation in design codes for

masonry, BS 5628 Part 1: 1985: Structural use of unreinforced masonry.

1:2:9 mortar1:1:6 mortar

1:1/2:41/2 mortar1:1/4:3 mortar

05

1015202530

0 20 40 60 80 100 120

Compressive strength of brick (N/mm2)

Com

pres

sive

stre

ngth

of w

all

(N/m

m2 )

Figure 2.1: Mean compressive strength of walls against brick strength for

102mm thick brickwork in various mortars (Hendry, 1990).

Brickwork strength can also be estimated by other simple relationship with

unit strength. Hendry et al. (1996) proposed that the compressive strength of

brickwork could be approximated to the square root of unit strength and to the third

15

or fourth root of the mortar cube strength. The Brick Development Association of

UK (1974) relates bricks with compressive strength of 35 N/mm2 to wall strength,

with a ratio of 0.3 to 0.35:1.

2.2.3 Effects of Brick Type and Geometry

The type and geometry of bricks whether solid, perforated, or hollow have

an effect on the compressive strength of masonry. Hendry (1990) reported an earlier

findings done by Schellbach (1971) on the compressive strengths of highly

perforated units, and reported that the highest ratio of masonry strength to brick

strength was obtained for bricks with perforation ratio of 38-43 %. Hendry (1990)

highlighted that holes of round shape or slots with round corners have no

distinguished effects on compressive strengths of brickwork, Conversely, a decrease

in compressive strengths of brickwork were observed for bricks with cores of

rectangular slots. Rectangular slots tend to initiate shear failure.

2.2.4 Effects of Test Methods and Measurements

The compressive strengths of brick are measured by loading bricks in

compression. Conventional tests require bricks to be loaded normal to its bed face

and the faces are capped or packed before testing to reduce the effects of roughness,

lack of plane and platen effects. Different materials could be used for packing or

capping. Malaysia/British Standard recommended soft capping using sheets of

plywood between loaded surfaces of bricks specimen. On the other hand, ASTM

specifies the use of hard capping consisting of either a thin layer of molten sulphur

compound or a gypsum plaster compound. Soft packing has the advantage of a

reduction in the time of preparation for testing and it has occasionally been claimed

that soft capping produced a more representative strength than hard capping

(Drysdale et al., 1994). Grimm (1975) highlighted that if a brick specimen is

unrestrained through the insertion of a teflon pad between brick and machine head

16

the compressive strength of the unit is further reduced. This is due to reduction in

effects of the machine platen.

Besides the influence of platen restraint and capping material, the

compressive strengths of bricks are also affected by the orientation of the specimen

during testing. Bricks tested on its bed, edge and end would give different

compressive strengths due to the different heights of the specimen. The platen effect

on the brick will be reduced with increase in height subsequently decrease its

compressive strength. Table 2.1 shows the work reported by Hendry (1997) on the

compressive strengths of bricks when tested in different orientations. Maximum

strength was achieved when tested on bed whilst minimum strength was obtained

when tested on end. Considerations for this shape factor are given its importance in

the European Standard prEN 771-1, which requires bricks compressive strength to

be declared with the intended orientation for testing.

Table 2.1: Compressive strengths of bricks tested in different

orientations (Hendry, 1997) Tested Brick type

On bed On edge On end

14 hole 74.3 26.2 10.4

10 hole 70.2 29.5 21.7

3 hole 82.0 53.2 40.2

5 slots 64.1 51.8 13.8

The influence on the shape factors was considered in the Australian Standard

AS/NZS 4456.4:1997, Masonry units and segmental pavers- Methods of tests. In

this standard, the compressive strength of brick is multiplied with a factor called the

aspect ratio factor, Ka which depends on the height to thickness ratio, to provide the

unconfined compressive strength. The unconfined compressive strength is given by

equation 2.3.

1000a

PC KA

= …(2.3)

Where,

C = unconfined strengths in megapascals.

17

P = total load at which the specimen fails in Kn.

A = net area in mm2

Ka = aspect ratio factor (Table 2.2)

Table 2.2: Aspect Ratio Factor (Ka) Height to thickness ratio 0 0.4 1.0 5.0 or more

Aspect Ratio Factor (Ka) 0 0.5 0.7 1.0

The curing of bricks specimen before testing also affects the compressive

strength of brick. Wet bricks tend to show lower strengths than dry ones. Grimm

(1975) reported that dry brick can be 15% stronger than wet ones.

2.3 Dimensional Tolerance

Fired clay bricks vary in size due to the varying property of natural clay and

variations in the manufacturing drying and firing conditions. The total variations,

which may take place due to variable shrinkage properties of clay during and after

manufacturing can account to approximately 5 to 15 % of original dimensions. Due

to the presence of this wide range of variability, dimensional tolerances are specified

in standards to achieve the desired dimensional consistency. This is important in

brickwork because it has been proven from research and observations that

dimensional variation would affect brickwork aesthetically as well as structurally

Bricks dimension should not vary more than the tolerance specified in

standards. Limits for dimensional tolerance is specified in facing brickwork to

ensure that sizes of bricks do not differ too much as to affect the appearance of a

wall. This is especially important for very short length walls and piers. Besides this,

research has also shown that careful control of dimensions would markedly increase

the speed of brick laying (Haller, 1964).

18

Previous research on masonry has shown that units with low dimensional

variation will produce a wall of higher compressive strengths. The use of bricks with

well-controlled dimensions is also essential for high strength brickworks since

brickwork with non-uniform joint thickness would be subjected to bending moments

and stress concentration. According to Grimm (1975), the compressive strength of

relatively short brick masonry prisms, built from conventional materials which were

concentrically loaded and tested in accordance to ASTM E477 (7) may be predicted

from the following equation:

' ' 8 2 6 11.42 10 ( 9.45 10 )(1 )m b cf f fζη ε− −= + × + …(2.4)

Where, '

mf = compressive strength of brickwork masonry prism

'bf = compressive strength of brick

ζ = prism slenderness ratio

η = material size factor

ε = workmanship factor and this factor depend upon the verticality of the

wall, dimensional variation and quality of mortar joints. For good

workmanship,

ε = 0.

It is evident from equation 2.4 that the dimensional variation constitutes the

workmanship factor, affects the compressive strength of brickwork.

Quality control measures during manufacturing are important to ensure that

bricks dimensions are within limits specified in standards. One of the causes for

variation lies partly with the mould and wearing of dies. Moisture movement within

the brick can also contribute to size variations after manufacturing. Clay bricks tend

to expand as they pick up moisture after being unloaded from the kilns. The

magnitude of this movement varies accordingly to types of bricks and brick firing

temperatures. About half of the expansion occurs within a few days after

manufacturing and the remainder gradually stabilised after a few months (Fig.2.2).

19

Therefore, generally bricks are only taken to the site two weeks after coming out

from the kilns.

71 100

Maximum Expansion

Expa

nsio

n

Days0

Figure 2.2: Expansion of kiln-fresh bricks due to absorption of

moisture from atmosphere. (Hendry et al., 1997)

2.4 Water Absorption

Water absorption of a brick is defined as the weight of water in a brick

expressed as a percentage of the brick’s dry weight. It varies roughly from 4.5 to 21

% and the variation is mainly due to the variable raw material and the manufacturing

process.

The extrusion process in the manufacturing produces denser brick in

comparisons to the moulded bricks and denser bricks in turn would exhibit less

absorption. This was proven through experiments (Sahlin, 1971), which showed that

extruded bricks contain small percentage of voids and therefore are less absorbent to

water.

The effects of bricks absorption property due to variable raw material used in

its manufacturing was shown by Surej et al. (1998) who reported the work carried

out by Kung (1987) on the effects of raw material to water absorption. The report

showed that within the normal brick firing temperature range, the water absorption

20

and the porosity of the burnt bricks increases with increasing calcium carbonate or

limestone content in the raw materials.

Water absorption of bricks is usually measured by the 5-hours boiling and

24-hours cold immersion test. The 24-hours cold immersion test allows water to be

absorbed into pores, which are easily filled under cold condition while the 5 hours

boiling test gives fully saturated condition where all pores are filled up with water.

The ratio of 24 hours cold immersion to maximum absorption in vacuum or

boiling (C/B ratio) gives the saturation coefficient, which is used to indicate bricks

durability. The saturation coefficient, which is actually a measure of the relative

open pore space present in brick is crucial during freeze-thaw action to

accommodate the volume change in water as it freezes. The saturation coefficient

ranges from about 0.4 to 0.95, the lower value of around 0.4 indicates high

durability and higher values of around 0.95, low durability (F. M. Khalaf and A. S.

De Venny, 2002).

Other durability indices have also been developed based on relationship of

porosity and water absorption. Table 2.3 shows the durability indices developed by

Surej et al. (1998). Theses durability indices, which are a function of porosity and

water absorption of bricks is shown in equation 2.5 and 2.6. DIAP(C) and DIAP(S)

refers to durability index based on absorption properties derived from the cold

immersion absorption property and the suction property respectively.

450.70 1( ) 387.98 0.87(2.94 )

CDIAP CB B

= + − + …(2.5)

450.70 4( ) 329.81 0.97(2.94 )

SDIAP SB B

= + − + …(2.6)

Where,

B is the absorption due to 5-hr. boiling.

C1 is the absorption due to 1-hr.immersion absorption.

S4 is the 4-hr. capillary suction achieved through similar test as in the initial

rate of suction.

21

Table 2.3: Limits of durability indices (Surej et al., 1998) Limiting Values

Index Durable Non-durable

DIAP(C) >90 <75

DIAP(S) >85 <70

Studies on the effects of water absorption to structural performance of fired

clay masonry shows that water absorption of masonry units has a relation with

flexural behaviour of masonry. Research carried out by the British Ceramic

Research Association on test wallettes to study the relationship of flexural strength

of brickwork and water absorption of bricks has derived the relationship between

flexural strength and water absorption (Figure 2.3). The curved line indicated in

brown is the 95 % confidence limit and this was approximated to the stepped line,

which relates to three levels of water absorption i.e. less than 7%, 7% to 12% and

beyond12% to the respective values of characteristic flexural strengths. These limits

of water absorption associated with the flexural strength of brickwork are used in BS

5628: Part 1 for design of laterally loaded walls (Table 2.4).

Table 2.4: Characteristic flexural strengths and levels of

water absorption (BS 5628 Pt. 1, 1985)

Characteristic flexural strength, fkx N/mm2

Plane of failure parallel

to bed joints Plane of failure perpendicular

to bed joints

Mortar designation (i) (ii) and

(iii) (iv) (i) (ii) and

(iii)

(iv)

Clay bricks having a water absorption less than 7% 0.7 0.5 0.4 2.0 1.5 1.2

Between 7 % and 12 % 0.5 0.4 0.35 1.5 1.1 1.0 Over 12 % 0.4 0.3 0.25 1.1 0.9 0.8

22

0

0.5

1

1.5

2

0 10 20 30

Water absorption %

Flex

ural

stre

ngth

N/m

m2

0

1

2

3

4

0 10 20 30

Water absorption %

Flex

ural

stre

ngth

N/m

m2

(a) (b)

0

0.5

1

1.5

2

0 10 20 30

Water absorption %

Flex

ural

stre

ngth

N/m

m2

0

1

2

3

4

0 10 20 30

Water absorption %

Flex

ural

stre

ngth

N/m

m2

(c) (d)

Figure 2.3 Relationship of flexural strength of brickwork with water

absorption of bricks in plane of failure (a) and (c) parallel to bed

joints and (b) and (d) perpendicular to bed joints (Morton, 1986)

2.5 Initial Rate of Suction

The initial rate of suction (IRS) denotes the amount of water sucked by the

brick upon contact with mortar during laying. The IRS, resulting from the presence

of capillary mechanism of the small pores in the bricks, is an important property in a

masonry construction since it affects the bond strength between the brick and mortar

thus affecting water tightness and durability of masonry.

BS Mortar Designation (i) 1 : ¼ : 3

BS Mortar Designation (iii) 1 : 1 : 6

23

Bricks with IRS less than 0.25 kg/m2.min can be considered as low suction

bricks whilst bricks with IRS more than 1.5 kg/m2.min can be regarded as high

suction bricks (Drysdale et al., 1994). Tests have indicated that IRS values between

0.25 to 1.5 kg/m2.min generally produce good bond strength when used with the

appropriate mortar designations. High suction bricks absorb water from the mortar

rapidly thus impairing bond properties. This water is needed for the proper hydration

of cement where the mortar contacts the brick. On the other hand, low suction bricks

do not absorb much water and hence the surplus water will float on to the surface of

mortar to result in poor initial and final bonding strength. However, recent tests to

evaluate the bond strength and water penetration of masonry built with low IRS

brick, demonstrated that flexural bond strength of very low IRS brick (less than 0.25

kg/m2.min) can equal or exceed those of higher IRA brick with proper selection of

mortar materials and type (BIA, 2001).

The initial rate of suction (IRS) is determined by the amount of water

absorbed through the bed face when immersed in 3mm depth of water for a period of

1 minute. The British Standard recognises the IRS as a crucial requirement for

highly stressed masonry and a test method to determine IRS is given in the appendix

of BS 3921:1985. However, no limit for IRS has been specified. On the other hand,

ASTM, gives guidance on limits for IRS. It recommends that bricks with IRS

greater than 30g/min per 30 in2 (equivalent to about 1.5 kg/ m2.min) should be

wetted prior to laying.

Wetting of bricks before laying are more vital for construction in hot weather

especially for highly absorptive bricks. However, the wetting of bricks has its

shortcoming. The bricks will have variable degree of wetness giving rise to variable

compatibility with mortar (Drysdale et al., 1994).

24

2.6 Soluble Salts Content and Efflorescence Effects

All clay bricks contain soluble salts originating from raw clay deposits. In a

brickwork, salts may also originate from mortar or drawn up from the ground.

Efflorescence, which is the white deposition of salts on bricks surfaces, occurs due

to the presence of these salts carried by water to the brick surfaces.

Salts leading to efflorescence are mostly sulphates of sodium, potassium,

magnesium and calcium salts. Efflorescence usually occurs in new constructions and

takes place when water-carrying salts evaporates leaving the salts depositions on

masonry surfaces. The dissolved salts in crystalline form lead to visible white stains

on surfaces but are normally harmless. However, in extreme cases, crystallisation

may take place within the brick causing internal stresses and leading to spalling and

cracking (Hendry et al., 1997).

Sulphate action occurs when water carries sulphate from bricks into mortar,

containing tricalcium aluminate, one of the constituents of Portland cement and

hydraulic lime. This reaction causes mortar to expand, causing cracking or spalling

of mortar joints and occasionally spalling of facing bricks. Hendry (1981) suggested

a limit for sodium sulphate content in bricks, which should not exceed 3% by weight

of a brick in order to avoid spalling and disruption of bricks surface.

2.7 Density

Raw materials and manufacturing process affects bricks density, which could

vary between 1300 kg/m3 to 2200 kg/m3. The density of bricks influences the weight

of walls and the variation in weight have implications on structural, acoustical and

thermal design of the wall. Incorrect assumptions on wall weight can result in

inaccurate dead loads and seismic loads, reduced factor of safety in shear walls and

overestimate of acoustical transmission loss (Grimm, 1996)

25

For acoustical design the sound resistance of a solid masonry wall is related

principally to its weight; the heavier the wall the less is the noise transmitted through

it. Typical sound insulation values for a 102.5 mm and 215 mm thick wall is shown

in Table 2.5. Loudness of 45 dB – 50 dB is considered as moderate loudness

suitable for average home and general office (Drysdale et al., 1994).

Table 2.5: Typical sound insulation values of masonry walls

(Curtin et al., 1995) Material and construction Thickness

(mm) Weight (kg/m2)

Approximate sound reduction index (dB)

Brick wall plastered both sides with a minimum of 12.5 mm thick plaster

215

415

49.5


102.5 220 46

In most existing standards for clay bricks density was not included as

requirements for standardisations. However, in the recent European Standard prEN

771-1: Specifications for clay masonry units, requirements for density should be

declared by the manufacturer for acoustic purposes. The specified tolerances for

density of test samples are graded as D1 and D2 with difference of ± 10% and ± 5%

respectively from the manufacturer’s declared values. The declared values may also

be intended for the calculation of load assumptions and thermal insulation.

One of the main functions of a wall is to provide some degree of thermal

insulation between the exterior and interior environments. Thermal considerations

for buildings include the comfort of users and the energy requirements of heating

and air conditioning equipment. Brickwork has relatively low resistance to thermal

effects, which means that brick is a good conductor of heat. Thermal resistance of

wall increases with the decrease in the density of the materials; hence, a wall’s

thermal resistance is increased by using bricks made of less dense or aerated

materials.

26

However, brick as a high mass building material has the inherent energy

saving features of thermal storage, which means that they are slow to heat up and

slow to cool down. This thermal inertia or thermal storage of brickwork is affected

considerably by its mass, which depended on the density of brick and therefore its

importance in the design load for both heating and cooling.

2.8 Bricks Specifications in International Standards

This section deals with the comparisons of bricks specifications for existing

standards, namely, British Standard (BS), American Standard (ASTM), Australian /

New Zealand Standard (AS/NZS), European Standard (EN) and Singapore Standard

(SS). Malaysian Standard (MS), which is adopted from the earlier version of the

British Standard, was also reviewed. The comparisons is aimed at developing a

better understanding on the way each parameter is being treated for standardisations

in accordance to a particular country’s requirements.

2.8.1 Compressive Strengths

The British Standard (BS 3921:1985) categorised compressive strengths into

classes of Engineering A and B (Table 2.6). These classifications of bricks are

commonly used for construction with aesthetics and strength requirements. All other

bricks and the damp proof-course bricks should have strengths not less than 5

N/mm2, however, the damp-proof course is divided into 2 in accordance to water

absorption.

27

Table 2.6: Classification of bricks by compressive strength and water

absorption (BS 3921:1985) Class Average compressive

strength (N/mm2) Water absorption (5-hr.

boiling) % by weight

Engineering A Engineering B Damp-proof course 1 Damp-proof course 2 All others

≥ 70 ≥ 50 ≥ 5 ≥ 5 ≥ 5

≤ 4.5 ≤ 7.0

≤ 4.5 ≤ 7.0

No limits

In the American Standards (ASTM), compressive strengths are classified in

accordance to the different grades of weathering and exposure conditions as

indicated in Table 2.7. The grades of weathering can be either negligible (NW),

moderate (MW) or severe (SW) depending on the map zoning as given in ASTM.

Table 2.7: Physical requirements for building bricks (ASTM C 62-

89a, 1990) Designation Minimum compressive

strengths brick flat wise lb/in2 (N/mm2)

Maximum water absorption (5-hr. boiling), %

Maximum saturation coefficient

Average of 5 bricks

Individual Average of 5 bricks

Individual Average of 5 bricks

Individual Grade SW 3000(20.7) 2500(17.2) 17.0 20.0 0.78 0.80

Grade MW 2500(17.2) 2200(15.2) 22.0 25.0 0.88 0.90

Grade NW 1500(10.3) 1250(8.6) No limit No limit No Limit No limit

Similar requirements of compressive strengths are given for Facing (ASTM

C 216 – 90a) and Hollow Bricks(ASTM C 652 – 89a) in the category of Grade SW

and MW. However, there is no category for Grade NW in both Facing and Hollow

Bricks.

In the Australian Standard (AS 1225 – 1984) the characteristics compressive

strength is specified, against values for the ratio of manufacturing height to

manufacturing width (Table 2.8).

28

Table 2.8: Characteristic compressive strength in accordance to

Australian Standard (AS 1225:1984) Ratio of manufacturing height to manufacturing width

Characteristics compressive strength, MPa

≤0.7 ≥2

7.0 5.0

In Singapore Standard (SS 103:1974) compressive strengths are classified as

First, Second and Third Grade with minimum compressive strength of 35 N/mm2, 20

N/mm2 and 5.2 N/ mm2 respectively.

It can be seen from the comparisons that the British Standard specified

stringent limits than the ASTM. A minimum compressive strength of 70 and 50

N/mm2 respectively for Engineering A and B was specified in the British Standard.

Whereas, in ASTM the minimum compressive strength specified for structural

facing bricks were 20.7 and 17.2 N/mm2 for Grade SW and MW bricks respectively.

On the other hand, the minimum specification for building bricks in ASTM for

structural or non structural use is higher, i.e. a minimum value of 10.3 N/mm2. The

BS specifies a value of 5 N/mm2. Likewise, a stringent water absorption limit of

minimum 4.5% was found in BS compared to a minimum of 17% in ASTM.

2.8.2 Water Absorption

The BS 3921:1985 defines the limits of water absorption in order to

categorise engineering bricks and bricks for damp-proof course (Table 2.6). The

standard specifies a low water absorption ( ≤ 4.5 %) to classify Engineering A bricks

and bricks for damp-proof course 1; higher water absorption ( ≤ 7.0 %) to classify

Engineering B bricks and bricks for damp-proof course 2. There is no limit of water

absorption for all other types of bricks.

Similarly, ASTM relates compressive strengths to water absorption but with

an additional parameter, the saturation coefficient (Table 2.7). However, the water

29

absorption limits in ASTM were less stringent than the BS. The limits given for the

designation of SW and MW are equal for all three types of bricks: Building, Facing

and Hollow. The maximum water absorption limits are given for the average of five

bricks and for individual bricks. For SW bricks the maximum water absorption

specified are 17 % while the MW bricks are 22 %. No water absorption limits are

required for the grade NW bricks.

On the contrarily, the Australian Standard (AS 1225 – 1984) which was set

up as a basic standard specifies the properties common to most bricks and put no

limit to the water absorption properties as well as the initial rate of suction.

However, it was mentioned in the standard that if the need arises such requirements

should be provided by the purchasers.

Singapore standard (SS 103:1974) specifies some general requirements for

water absorption. The water absorption is limited to 25 % for common bricks, and

no requirement is set for facing bricks. This is probably due to the reason that

brickwork being widely used as infill walls there, which do not require structural or

facing bricks and therefore the water absorption is not critical.

On similar trend with the Australian Standard, water absorption was not

considered as a basic requirement for product description and designation in

European Standard prEN 771-1. Requirements for water absorption will depend on

its relevance in construction and in this case, the limits are to be declared by the

manufacturers.

2.8.3 Initial Rate of Suction (IRS)

British Standard BS 3921:1985 does not specify any limit for IRS. However,

a test method for determining this value is included in Appendix H of the standard.

30

ASTM specified that bricks to be tested for IRS, if the value exceeded

1.5 kg/ m2.min in which case for applications, bricks are to be wetted. The European

Standard prEN 771-1 does not specify any limits for IRS but these values will have

to be declared by manufacturers when relevant to the uses for which the unit is put

on the market. The mean IRS of the sample tested should fall within the range of the

declared values.

The Australian Standard does not specify any requirements for IRS, however

a test method to determine IRS is provided in AS/NZS 4456. Singapore Standard

SS 103:1974 and Malaysian Standard MS 76:1972 specifies no requirement at all on

IRS since both standards were developed using BS 3921:1969 as reference whereby

the initial rate of suction was not accounted for.

2.8.4 Dimensional Tolerance

Sizes and tolerance specified by the British Standard BS 3921:1985 are

meant only for the 225 mm × 112.5 mm × 75 mm format bricks. Requirements for

other bricks format are given in separate standards such as BS 4729(special shapes).

In BS 3921:1985, dimensional tolerance is measured by the deviations in the

overall length, width and height based on 24 bricks (Table 2.9). In addition,

individual brick dimension should not exceed the coordinating size for length, width

and height. Coordinating size is the work size including the allowance for mortar

joints and tolerances and work size is the manufactured size. The overall

measurement is based on the expectation that individual brick dimension should not

differ from the work size by more than 6.4 mm for length whilst 4.0 mm for both

width and height.

31

Table 2.9: Dimensional tolerance based on measurement of 24 bricks

and coordinating and work size in accordance to British

Standard (BS 3921:1985) Coordinating size

Work size Overall measurement of 24 bricks

mm 225 112.5 75

mm 215 102.5 65

Maximum (mm) 5235 2505 1605

Minimum (mm) 5085 2415 1515

Dimensional variations are used in the Australian Standard (AS 125 – 1984)

to classify the categories of bricks. The categories are as follows:

ST0 – bricks not required to be precise in dimensions

ST2 – bricks manufactured to finer tolerances for special applications.

ST3 – bricks where regularity in size is necessary

Limits in dimensional tolerance (Table 2.10) for each of these categories are

based on the variations of length, width and height of 20 bricks for the respective

dimensions. In addition, the length shall not be less than 1.5 times the width or not

exceeding 390 mm. The height shall not be greater than 70 percent of the length.

Table 2.10: Dimensional tolerance in accordance to Australian

Standard (AS 1225 – 1984)

Dimensional tolerance of 20 bricks Size Category

Length

Width Height

ST0 ST2 ST3

± 90 mm ± 40 mm ± 60 mm

± 50 mm ± 25 mm ± 40 mm

± 50mm ± 25 mm ± 40 mm

General criteria for dimensions and proportions (a) Length not less than 1.5 times width nor more than 390mm (b) Height shall not be greater than 70 percent of length.

Tolerance on dimensions specified by ASTM is based on a sample of 10

bricks and each brick should not lie outside the tolerance limits given in the

respective standards for Facing, Hollow and Building bricks. Table 2.11 shows the

tolerance limits for facing bricks. Unlike the British Standard, variations in

32

dimensions are not given in terms of length, width and height but are specified with

respect to some intervals of dimensions. Dimensional variations for facing and

hollow bricks are classified into categories defined by usage, exposure and

architectural requirements corresponding to Type FBX and FBS. In addition, the

facing and hollow bricks are also required to satisfy the tolerances on distortion and

out of square.

Table 2.11: Dimensional tolerance of facing bricks in

accordance to ASTM C 216-90a (1990) Maximum permissible variation from specified dimension, plus or minus (mm)

Specified dimensions, (mm)

Type FBX Type FBS

76 and under 76 to 102, incl. 102 to 152, incl. 152 to 203, incl. 203 to 305, incl. 305 to 406, incl.

1.6 2.4 3.2 4.0 5.6 7.1

2.4 3.2 4.7 6.4 7.9 9.5

Note: FBX: Brick for general use in exposed exterior and interior walls where a high degree of mechanical perfection, narrow colour range and minimum permissible variation in size are required. FBS: Brick for general use in exposed exterior and interior masonry walls where wider colour ranges and greater variation in sizes are permitted than are specified for type FBX.

In European Standard prEN 771-1, the dimensional tolerances are specified

under three categories i.e. T1, T2 and T0 and the respective tolerances for each

category are to be computed using the formula, which depends on the work size

dimensions (Table 2.12). The mean values for all dimensions i.e. the length, width

and height in a sample of 10 bricks should not exceed the declared values by the

respective tolerance in the category. In addition, for works, which require acoustical

property, dimensional tolerance in terms of the range values from a measurement of

10 bricks in a sample should be within the categories given in Table 2.13.

33

Table 2.12: Dimensional tolerance for mean value of work size in

accordance to European Standard (prEN 771-1, 2000) Category Tolerance

T1 0.40 (work size dimension) mm or 3mm whichever is greater±

T2 0.25 (work size dimension) mm or 2mm whichever is greater±

T0 A deviation in mm declared by the manufacturer

Table 2.13: Dimensional tolerance for range of work size in

accordance to European Standard (prEN 771-1) Category Maximum range

R1 0.6 (work size dimension) mm

R2 0.3 (work size dimension) mm

R0

A range in mm declared by the manufacturer

In Singapore Standard (SS 103: 1974) the dimensional tolerance are

categorised as First, Second and Third Grade in accordance to the dimensional

deviations of the overall measurements of length, width and height of 24 bricks

respectively (Table 2.14).

Table 2.14: Classification of bricks in accordance to dimensional deviation

limits in Singapore Standard (SS 103: 1974)

Overall measurements of 24 bricks (mm)

First Grade Second Grade Third Grade

Length 5085 to 5235 5280 to 5472 Width 2415 to 2505 2445 to 2580

Height 1530 to 1620 1704 to 1800

Bricks satisfying all other requirements but having dimensions and compressive strength outside First Grade and Second Grade.

34

2.8.5 Efflorescence

In the British Standard, the levels of efflorescence of bricks are categorised

either as slight, moderate and heavy (Table 2.15). Bricks showing efflorescence in

the heavy category is considered as not complying with the standard. An evaluation

for efflorescence is based on the visual examination of 10 specimens in a sample,

tested in accordance to Appendix C of BS 3921:1985. Slight efflorescence refers to

bricks with up to 10 % of its surface area contaminated with salts and more than 10

% but not exceeding 50 % are categorised as moderate whilst heavy category refers

to bricks with more than 50 % of its surface area affected. In addition, the heavy

category of efflorescence is accompanied by powdering and flaking of the surface.

Table 2.15: Levels of efflorescence in British Standard (BS3921: 1985) Nil No perceptible deposit of salt

Slight Up to 10% of the area of the face covered with a deposit of salt, but

unaccompanied by powdering or flaking of the surface.

Moderate More than 10% but not more than 50% of the area of the face covered with a deposit of salts but unaccompanied by powdering or flaking of the surface.

Heavy More than 50% of the area of the face covered with a deposit of salts and/or powdering or flaking of the surface.

In ASTM requirements for efflorescence is meant only for facing and hollow

bricks. The test method and rating based on 5 pairs of bricks are given in ASTM C

67 – 90a. The bricks are rated as effloresced if perceptible differences are noted and

otherwise. The standard requires bricks of rating not effloresced.

In the Australian Standard (AS 1225 – 1984) the level of efflorescence for

brickwork constructed for appearance should not exceed the limits defined by the

slight category (Table 2.16). The classification is based on the worst case of

efflorescence category occurring in the 5 pairs of bricks tested.

35

Table 2.16: Levels of efflorescence for the Australian Standard

(AS 1225 – 1984)

Nil No observable efflorescence

Slight Not more than 10% of the total external above-water surface covered by a deposit of salts.

Moderate More than 10% of one external above-water surface but not more than 50% of the total external above-water surface covered by a deposit of salts.

Heavy A deposit of salts covering more than 50% of the total external above-water surface.

Severe Any efflorescence that is accompanied by powdering or flaking of the surface of the specimen.

The Singapore standard specifies level of efflorescence similar to the British

standard, however with the addition of another category designated, ‘Serious’. This

level refers to cases where a heavy deposit of salts, accompanied by powdering

and/or flaking of the surface and tending to increase with repeated wetting of the

specimen. Facing bricks and common bricks should not exceed the conditions stated

for slight and the moderate efflorescence (Table 2.17).

Table 2.17: Levels of efflorescence in Singapore Standard

(SS 103:1974) Nil No perceptible deposit of salt

Slight Not more than 10% of the area of the face covered with a

thin deposit of salt.

Moderate A heavier deposit than ‘slight’ and covering up to 50% of the face, but unaccompanied by powdering or flaking of the surface.

Heavy A heavy deposit of salts covering 50% or more of the area of the face but unaccompanied by powdering or flaking of the surface.

Serious A heavy deposit of salts accompanied by powdering and/or flaking of the surface and tending to increase with repeated wettings of the specimen.

36

2.8.6 Soluble Salt Content

In the British Standard (BS 3921:1985) bricks are classified as Low (L) and

Normal (N) indicated by the salt content. The normal category (N) assumes no limit

on soluble salt content while the low category (L) should have salt content not

exceeding the values given in Table 2.18.

Table 2.18: Maximum salt content for the low category (L)

in accordance to British Standard (BS 3921:1985) Soluble salts Maximum content %

Sulphate Calcium Magnesium Potassium Sodium

0.5 0.3 0.03 0.03 0.03

The Singapore Standard (SS 103:1974) specifies a total salt content of 1%

and 2% for Facing and Common bricks respectively. In addition, the Standard also

specifies the content of sulphuric anhydride (SO3), which should not exceed 0.3%

by mass for all the three grades of bricks classifications.

The Australian standard (AS 1225 - 1984) and the ASTM do not include any

requirements for soluble salt content. However, a test to determine the resistance of

bricks to salt attack is given in the Australian Standard, AS/NZS 4456.10:1997. In

this test, specimens are subjected to cycles of soaking in salt solution, oven drying

and cooling. The specimens are then weighed to determine the total mass lost and

this is used to define the salt attack resistance categories i.e. exposure, general

purpose and protected.

The recent European Standard prEN 771-1 designate soluble salt content in

bricks in terms of category of application i.e. S0, S1 and S2 as shown in Table 2.19.

S0 is suitable for completely dry applications, S1 is for normal exposure condition

and S2 is meant for masonry structures subjected to prolonged saturation. There is

no requirement for salt limits in the S0 category of application. An example of such

37

application is in rendered walls where protection from water and moisture

penetration is provided by the layer of plaster applied on bricks surfaces.

Table 2.19: Soluble salt content categories in accordance to

European Standard (prEN 771-1) Total % by mass not greater than Category

Na+ + K+ Mg 2+

S 0 No requirement No requirement

S 1 0.17 0.08

S 2 0.06 0.03

There is no limit given by the pr EN 771-1 on the sulphate content and it was

noted in the standard that consideration on this may be dealt with in national design

codes. There is no requirement for calcium and potassium and sodium is given in

combined form.

2.9 Tests Methods and Measurements in International Standards

2.9.1 Methods of Sampling for Tests in International Standards

Bricks to be tested are to be selected at random from a lot. A lot consists of

the whole population of bricks to be tested. The bricks selected from the lot would

constitute the samples, which are representative of the bricks population. Methods of

sampling and sample size i.e. the number of bricks in a sample could vary from one

standard to another. American Standard specifies the lot size for samples (for the

compressive strength and absorption determinations) as 250,000 brick. For larger

lots 5 bricks are to be selected from each 500,000 brick. The British Standard

limited the lot size as not greater than 15,000 bricks. The lot size was not specified

exactly in the Australian Standard (AS/NZS 4456.1:1997). It states that:

For testing a lot, the sample shall comprise masonry units selected

as representative from an identifiable lot and the test results shall

apply to that lot.

38

The sample size required for the various tests differs according to the

standard requirements as illustrated in Table 2.20.

Table 2.20: Sample size for tests in international standards

Number of bricks required for tests in standards

Tests

BS 3921 ASTM AS/NZS

4456

SS 103 PrEN 771-1

Compressive strength 10 5 10 10 10

Cumulative dimensions 24 - 20 24 -

Individual dimensions 24 10 20 24 10

Water absorption 10 5 10 10 10

Initial rate of suction - 5 10 - 10

Efflorescence 10 10 10 10 -

Salts content 10 - - 10 10

Density - - 5 - 10

The British Standard adopts a larger number of sample size for dimensional

tests whilst the number of bricks were kept to 10 for testing other parameters. The

Singapore Standard and Malaysian Standard were derivations from British Standard,

therefore similarity in the number of bricks used in the respective tests. The ASTM

and Australian/New Zealand Standard are based on metrics, therefore sampling was

based on 5 and 10 units respectively. The European Standard is more consistent in

that all tests are restricted to 10 bricks.

2.9.2 Compressive Strengths

The Compression tests used for determining the brick compressive strength

are carried out differently for various standards (Table 2.22). For example, the

packing materials used are different for test conducted in accordance to BS and

ASTM. Whilst the BS used plywood, the ASTM favours the use of hard capping

made of gypsum and sulphur. Conversely, the European Standard requires bricks

surfaces to be grounded to parallel tolerance before testing.

39

The rate of loading applied to the bricks differ in each standard, and could

vary throughout each test, except for AS/NZS, which adopt a constant loading

method.

The calculation of compressive strength also differs among the standards. BS

3921, ASTM C67 and SS 103 based their calculation on gross area. On the other

hand, AS/NZS 4456 compute the compressive strength based on net area, which

gives a higher value of compressive strength compared to calculation using net area.

In general, the ASTM implement an entirely different test approach

including the number of specimens, curing condition and capping material in

comparison to others.


Table 2.23 shows the comparisons of the test and measurement methods used

in determining the water absorption of bricks in the various standards. British and

Singapore Standard only adopted the 5-hours boiling test, whereas ASTM specified

both the 5-hours boiling and the immersion tests. These two tests are required for the

determination of the saturation coefficient, which is the ratio of absorption by 24-hr

immersion in cold water to that of the 5-hr boling.

The Malaysian Standard MS 76:1972 allows two alternative methods to

measure water absorption i.e. the 5-hours and the vacuum method, which is similar

to the earlier version of the British standard. However, in BS 3921:1985 only the 5-

hours boiling test is specified since research has shown that there is no simple

relationship between these two methods and results of the two tests could be

different.

The European standard prEn 771-1 specifies the 24-hr water immersion test

to determine water absorption. Water absorption measured by the 24 hr immersion

40

would apparently show a lower value of water absorption in comparison with the 5-

hr. boiling test.

A new method of test for water absorption was introduced recently (Khalaf

and DeVenny, 2002). In this test, 20 mm-brick lumps instead of full brick units were

used. Table 2.21 shows the comparison of results between whole brick and the 20-

mm brick lump for the 24-hr cold immersion and the 5-hr. boiling tests. The results

showed that the5-hrs boiling test underestimates the absorption of bricks. In

addition, results for the 5-hr boiling test were almost equivalent to the 24-hr cold

immersion for the brick lump and in this respect; the saturation coefficient could not

be measured. However, it should be noted that the test for cold immersion was

carried out after bricks were vacuum. The advantage of this new test is that it could

be conveniently carried out without the necessity of big tanks for boiling of whole

bricks and thus saving on the fuel consumption.

Table 2.21: Comparison of water absorption from 5-hr boiling and the

24-hr cold immersion tests using whole brick and brick lumps

(Khalaf and DeVenny, 2002)

Brick type

Water absorption of brick units BS 3921 (5-hr boil) (%)

Water absorption of brick units (24-hr cold) (%)

Water absorption of brick lumps (5-hr boil) (%)

Water absorption of brick lumps (24-hr cold) (%)

Class B Engineering

6.0 5.2 6.3 6.2

Clay 10-hole 6.2 4.6 7.4 7.2

Clay 3 slot and 8 hole

5.8 5.3 7.4 7.4

Clay frogged common

12.9 10.3 14.1 11.5

Granite 2.63 2.55 2.63 2.55

Besides implementing the different types of test for the measurement of

water absorption there are also some differences observed in the number of bricks

used and preparation of specimens before testing. ASTM requires five half-brick

while AS/NZS and BS specify the use of 10 whole bricks. Another difference is in

the duration for attaining constant mass when drying bricks in the oven. BS 3921

41

assumes 48 hours of heating in the oven to achieve constant mass whereas the

AS/NZS and ASTM monitor the weight loss during drying and constant mass is

assumed if subsequent drying indicate that the change in mass is not greater than

0.1 % of the previous weight for the AS/NZS and 0.2 % for ASTM.

2.9.4 Initial Rate of Suction

Table 2.24 shows the comparisons of test and measurement methods for the

initial rate of suction as required by the various standards. The tests principles are

similar in all standards, whereby bricks capillary suction is measured by immersing

bricks in about 3 mm depth of water for a duration of 1 minute. The ASTM and the

Australian Standard specify some means to set up the apparatus in maintaining water

level to the required height of immersion.

In the Australian / New Zealand Standard (AS/NZS 4456:1997) IRS are

given in terms of Anet and Agross as shown in Table 2.24. The ASTM specified that

the IRS measured for cored bricks should be modified with a factor depending on

the net area of immersion, which will result in a higher value of IRS compared with

calculation based on gross area. The BS on the other hand based its IRS calculation

on the gross area of immersion.


Methods of testing to determine dimensional tolerances vary between the

standards (Table 2.25). British, Australian/New Zealand, Malaysian and Singapore

standard specify dimensional tolerance measured from the cumulative dimensions of

specified numbers of bricks, whereas, ASTM and European standard specify an

individual brick dimensional tolerance. Other variations include the numbers of

bricks required for the cumulative dimensions and the methods of measuring the

tolerance.

42

ASTM based their tolerance on a sample of 10 bricks and each brick should

not depart from the specified size by more than the tolerance given in the standard.

While, the British and Singapore standard establish the tolerance limits based on two

approaches namely (i) individual dimension (ii) the overall measurement for 24

bricks. While AS/NZS, tolerance limit is based on overall measurement of 20 bricks.

The European standard specifies an entirely different dimensional tolerance

limit based on the mean and range values for a sample of 10 bricks according to the

different categories. The mean deviation refers to basic requirement and constitute a

minimum description of a unit whilst the range is only required when relevant to the

needs of application. In addition, European standard also specified some geometry

requirements for bricks to be used in elements subjected to acoustics requirements.

2.9.6 Efflorescence

The test for efflorescence in existing standards involved cycles of wetting

and drying of bricks in laboratory after which they are examined for the salts

depositions on the surface. The procedures for quantifying efflorescence differ

between the standards (Table 2.26). British standard and Australian/New Zealand

standard categorise efflorescence into levels in accordance to the degree of

contaminants. In contrast, the ASTM quantify efflorescence in bricks either simply

effloresced or not effloresced. The new amendments made to BS 3921 in 1995

ignored the effects of efflorescence. Similarly, European Standard prEN 771-1 does

not specify any requirement for efflorescence in bricks.

43

Table 2.22: Test methods and measurements for compressive strength in international standards

Test Standards

Sample size

Preparation of specimen Speed of testing Capping material Compressive strength

calculations

BS 3921 Appendix. D

10 (Whole brick)

Immerse brick in water for 24 hrs or saturate by boiling

Convenient rate not exceeding 35 N/(mm2.min) until half of expected max. load after that reduces to 15 N/(mm2.min) until failure.

Soft capping: three-ply 4mm thick plywood

Maximum load

smaller bed of the overall dimension

ASTM C67-90a

5 (Half brick)

Dry specimen in the oven for not less than 24 hrs.

Convenient rate until about half of expected maximum load after that uniform rate.

Hard capping: • Gypsum • Sulphur

Maximum load

Average of gross area of upper and lower bearing surfaces

AS/NZ 4456:1997

10 (Whole bricks)

Moisture content as sampled

Constant rate within a range equivalent to a stress of 150 kPa/s (9 N/mm2.min) to 700 kPa/s (42 N//mm2.min)

Soft capping: • 4 -6 mm plywood • 12mm fibreboard

Unconfined 1000a

PC KA

=

where, aK = aspect ratio factor A = net area

PrEN 771 – 1

10 (Whole bricks)

Bricks tested dry Not available No capping needed. Surfaces ground to a parallel tolerance

Not available

44

Table 2.23: Test methods and measurements for water absorption in international standards

Test Standards

Sample size

Type of test Determination of dry mass Test procedures Calculation of water absorption

BS 3921 Appendix. E /SS 103

10 (Whole brick)

5-hour boiling test

Drying – in oven (110 ±8°C) for at least 48 h. Cooling – bricks left unstacked in a ventilated room for 4 h, with 2 h of continuous air using an electric fan. Dry mass is determined when bricks are cool.

5-hr.boiling – Bricks are boiled in a tank of water for 5 hrs. Then are cooled naturally in the water for not less than 16 hours nor more than 19hrs.Then take the weight (wet mass).

(wet mass-dry mass)100

dry mass%

Average of 10 specimens to the nearest 0.1%.

ASTM C67-90a

5 (Half brick)

i) 5-hour boiling and ii) 24-hour immersion test.

Drying – in oven (110 to 115°C for not less than 24 h and until two successive weighing at intervals of 2 hrs. show an increment of loss not greater than 0.2% of previous weight. Cooling – in a room temperature maintained at 24 ± 8°C, relative humidity 30 – 70%. Record the average dry mass of all specimens as Wd.

Immersion test – submerge cool bricks in clean water at 15.5-30°C, for 24 h. Then remove specimens wipe dry and weigh. Record the average weight of all specimens as Wsc. 5-hr.boiling – bricks are boiled in a tank of water for 5 hrs. Then cool naturally to 15.5-30°C. After that remove specimens wipe dry and weigh. Record the average weight of all specimens as Wsb.

Absorption by immersion: =(Wsc-Wd)/ Wd Absorption by boiling: =(Wsb-Wd)/ Wd (Saturation coeff. = absorption by immersion / absorption by boiling)

AS/NZ 4456.14: 1997

10 (Whole bricks)

i) 5-hour boiling and ii) 24-hour immersion test.

Drying – in oven (110 ±8°C) until consecutive weighing at intervals of 4 hrs show a change in mass of not greater than 0.1 %. Record the lowest average weight for all specimens at room temperature as the dry mass m1.

Immersion test – submerge cool bricks in clean water at ambient temperature, for 24 h. Then remove specimen wipe dry and record the average mass of all specimens as m2. 5-hr boiling – bricks are boiled in a tank of water for 5 hrs. Then cool naturally to 15.5-30°C. Then take this saturated weight and record the average mass of all specimens as m3.

Absorption by immersion: Wi (%) = 100(m2-m1)/ m1 Absorption by boiling: Wb (%) = 100(m3-m1)/ m1 Saturation coefficient = Wi / Wb

prEN 771 - 1 10 (Whole bricks)

24-hour immersion test.

Not available Not available Not available

45

Table 2.24: Test methods and measurements for initial rate of suction in international standards

Test Standards

Sample size Preparation of specimen Test procedures Initial rate of suction calculations

BS 3921 Appendix. H

Not specified

The bricks are dried in the oven as in absorption test. The weight of the dry brick is recorded as

1m in gm.

The dry brick is immersed in water at a depth of 3 ± 1mm for 1 min. Record this weight 2m in gm.

22 1

2

1000( ) in kg/m .min .

where = gross area of the immersed face of the brick in mm

m mIRS

AA

−=

ASTM C67-90a

5 (Whole brick)

i) Oven drying as in absorption test or ii) Ambient air drying The weight of the dry brick is recorded as 1m in gm.

The dry brick is immersed in water at a depth of 3 ± 1mm for 1 min. Record this weight as

2m in gm. Some means of maintaining water level at a depth of immersion of 3 ± 1mm is provided in the standard.

IRS = 1 2m m− in gm. IRS is measured in gm/min/30 in2. For cored bricks the measurement of IRS i.e. 1 2m m− has to be multiplied

with a factor of 30net area

.

AS/NZS 4456.17: 1997

10 (Whole brick)

Bricks are dried in the oven as in absorption test. The weight of the dry brick is recorded as 1m in gm.

The dry brick is immersed in water at a depth of 3 ± 1mm for 60 ±1 sec. Record this weight

2m in gm. A set up of the apparatus suggesting a way of maintaining immersion at depth of 3 ± 1mm is provided in the standard.

2 1

2 1

1000( )

1000( )

grossgross

netnet

m mIRS

Am m

IRSA

−=

−=

IRS (kg/m2 .min) for each brick and mean of the 10 specimens.

prEN 771 - 1 10 (Whole bricks)

Not available

46

Table 2.25: Test methods and measurements for dimensional tolerance in international standards

Measurement of dimensional tolerance Test Standards Individual brick dimension Cumulative (overall dimension)

BS 3921 Appendix. A

1. Each brick from the 24 bricks for the cumulative measurements must not exceed the coordinating size as given in Table 2.9.

1. Cumulative dimensions of 24 bricks must not exceed the specified range for length width and height as indicated in Table 2.9. The cumulative measuremen is based on the assumption that each brick should not differ from the work size by more than 6.4mm for length, 4mm for width and height.

ASTM C67-90a

1. Each brick from the 10 bricks in a sample should not vary from the specified allowable dimensional tolerance as given in Table 2.8

2. Tolerance on distortion and out

of square is also specified for facing bricks.

No cumulative dimension specified

AS/NZS 4456.17: 1997

1. Each brick from the 20 bricks should

comply with the general criteria as given in Table 2.7.

1. Cumulative dimensions of 20 bricks must not exceed the specified range for length width and height for the three categories (Table 2.10). These categories identify bricks tolerance requirements: ST0 – bricks no required to be precise in dimensions ST2 – bricks manufactured to finer tolerance for special application ST3 – bricks where regularity in size is necessary.

47

Table 2.25 (cont.): Test methods and measurements for dimensional tolerance in international standards

Measurement of dimensional tolerance Test Standards

Individual brick dimension Cumulative (overall dimension)

PrEn 771-1 1. Mean dimensions for the test sample should not be greater than declared means for categories T1, T2 and T0

Where,

T1: 0.40 (work size dimensions) mm or 3 mm whichever is greater±

T2: 0.25 (work size dimensions) mm or 2 mm whichever is greater± T0: a deviation in mm declared by the manufacturer.

2. The declared range should be within the range determined within the test sample for the categories R1, R2 and R0

Where, R1: 0.60 (work size dimensions) mm±

R2: 0.30 (work size dimensions) mm± R0: a range in mm declared by the manufacturer.

No cumulative dimension specified

48

Table 2.26: Test methods and measurements for efflorescence in international standards

Test Standards

Specimen Numbers Test procedures

Measurements of efflorescence

BS 3921 Appendix. C *

10 (Whole brick)

One face of the brick is subjected to 2 cycles of wetting and drying for the specified time. Then examined for efflorescence by comparing this face with the other faces that is not subjected to the wetting and drying cycles.

Levels for efflorescence as shown in Table 2.7. Bricks are categorised according to the worst occurrence. Bricks with ‘Heavy’ efflorescence are considered as not complying with the standard.

ASTM C67-90a

5 pairs (Whole brick)

One specimen from each pair is allowed to stand on ends partially immersed in water for 7 days. The other pair is kept in a room with specified humidity and temperature. Then dry both sets in oven for 24 hrs. After that compare and examine both sets for efflorescence.

Efflorescence is recognised as either ‘effloresced’ or ‘not effloresced’

AS/NZS 4456.6: 1997

5 pairs (Whole brick)

One specimen from each pair is allowed to stand on ends partially immersed in water for 7 days then air dry for 2 days. After that compare and assessed with respect to a matching brick.

Levels for efflorescence as shown in Table 2.13. Bricks are categorised according to the worst occurrence. Bricks exposed to view should not exceed ‘slight’.

prEn 771-1

No requirements

*Note: Efflorescence test has been removed from BS 3921 (AMD 8946/December 1995)

49

2.10 Conclusions

A considerable amount of past research and studies on masonry indicated the

relationship between masonry strength and unit strength. An example of such

relationship developed by Hendry (Equation 2.1 and 2.2) and is used in the code for

masonry design (BS 5628:1985). The compressive strength is therefore one of the

most important bricks properties for design requirements, and dealt by

specifications.

The compressive strengths of bricks can vary from 5 N/mm2 to over 100

N/mm2, depending upon materials and types of manufacturing and to some extent

are affected by the methods of testing in evaluating the compressive strength.

Malaysia Standard / British Standard identifies its clay bricks as Engineering A and

B (compressive strength ranging from more than 70 N/mm2 to not less than 50

N/mm2) for structural purposes and as ‘All others’ for strengths above 5 N/mm2. On

the other hand, ASTM classifies bricks into three categories i.e. building, facing and

hollow, with a minimum compressive strength of 20.7 N/mm2 and 17.2 N/mm2 to be

used in regions of severe (SW) and moderate weathering (MW) respectively. Grade

NW bricks with minimum compressive strength of 10.3 N/mm2 is meant for

applications in regions with negligible weathering. Singapore Standard defines

bricks as First, Second and Third Grade in accordance to the levels of compressive

strengths, with a minimum value of 5.2 N/mm2 for general purpose construction.

The methods of testing compressive strength are known to affect the

computed values obtained in standards. The usage of soft capping specified by the

British and Australian/New Zealand Standard is believed to reduce platen restraints.

Platen restraint induces artificial strengthening thereby enhancing the compressive

strength. Hard capping is used in ASTM and European Standard prEN 771-1 uses no

capping material, however requires the surfaces to be ground parallel and free of

irregularities.

The British, ASTM, Malaysian and Singapore standards based the evaluation

of compressive strength upon bricks tested on bed faces with the exception of

Australian/New Zealand, which accommodate the compressive strength for tests in

50

other orientations, producing a different height to thickness ratio (h/t) depending on

the bricks orientation in the tests. The aspect ratio, h/t, has a considerable effect on

the compressive strength, the higher the ratio the least is the compressive strength.

Subsequently, bricks tested on the bed face (lowest h/t ratio) display the largest

compressive strength. The development of European specification for masonry units,

prEN 771-1 introduces similar test methods to Australian/New Zealand Standard,

but the strength limits are to the discretion of the manufacturers declared values. The

EN and Australian approach of defining the unit strength in various orientations

provide a comprehensive information on the unit and this is useful for structural

design purposes.

Amongst others the compressive strength of units are affected by the curing

methods. Previous research; tend to indicate higher strength for dry bricks as high as

15 % greater than cured bricks. Evaluation of compressive strengths by ASTM and

European Standard was based on dry bricks in contrast to British, Malaysian, and

Singapore standards, which cured the bricks by saturating them in cold immersion or

by boiling. On the contrarily, Australian/New Zealand Standard carried out the

compressive strength on bricks as received i.e. the bricks having a moisture content

as sampled. However, if the bricks moisture content exceeds 25 %, air-drying is

required.

Most masonry standards dictate the requirements of water absorption for

bricks with structural applications and cases where resistance to water and moisture

penetration are critical. For example, in British Standard BS 3921: 1985 low water

absorption limits is specified for Engineering A and B and damp-proof course 1 and

2 bricks with water absorption of ≤ 4.5 % and ≤ 7.0 % respectively. Bricks for other

applications than those already mentioned are not restricted to any water absorption

limits. Similarly, masonry specification in ASTM C 62-89a, ASTM C 652-89a and

ASTM C 216-90a specified limits for water absorption of bricks with high levels of

compressive strengths where applications are specifically for severe and moderate

weathering regions. For negligible weathering regions bricks are not required to

conform to any limits of water absorption.

51

The Australian Standard, AS 1225-1984, is a general standard for all

masonry materials and does not specify limits for water absorption however has

included test methods for determining these values. The European Standard for

masonry units (pr EN 771-1), specifies water absorption requirements for bricks to

be used in external applications and the value is as declared by the manufacturers.

Recent research indicated the existence of some relationship between water

absorption to bricks porosity and compressive strength. The research revealed that

bricks with the least water absorption and small porosity produce higher

compressive strengths and this relationship could be used as an early indicator for

compressive strength. Other studies carried out on the relationship of water

absorption and bricks porosity had established durability indices, which provide

guideline for resistance of masonry against the freeze and thaw actions. These

indexes provide limits that can be used to identify durable and non-durable bricks.

The two types of test methods used for measuring water absorption i.e. the 5-

hours boiling and 24-hours cold immersions are known to give different

measurements. The 5 hours boiling test provides results for saturated conditions,

while the 24 hours cold immersion gives partial saturation. The prEN 771-1 requires

water absorption of bricks to be determined by the 24 hours cold immersion test,

hence producing a lower value of water absorption measurement.

The IRS is the rate at which a brick sucks water from mortar during laying

and therefore affects the bond strength between units and mortar. The suction

properties are crucial to the design of walls subjected to lateral load particularly in

highly stressed masonry structures. The IRS does not form an integral part of the

specifications for both the Australian/New Zealand and British Standards. However,

testing method to determine IRS is provided by the standards. On similar grounds

the European standard pr EN 771-1, requires IRS to be specified for relevant cases

of applications and the value of IRS to be declared by the manufacturer. In contrast,

ASTM requires the IRS values for bricks to be known and recommends that bricks

to be wetted before laying if the IRS is higher than 30 g/min per 30 in2 (1.5

kg/min/m2). The practice of wetting bricks before laying ensures proper bond

development between mortar and the highly absorptive bricks. In highly stressed

52

structures a good bond between mortar and bricks is essential to prevent the

occurrence of cracks in mortar joints and thus enhancing the water-tightness

property of facing brickwork.

The dimensions and tolerances of bricks are used to describe and designate

masonry units in standards. Dimensional variations are expected due to the

shrinkages in the natural clay deposits, which take place during drying and burning

processes. The standards specified dimensional tolerances to restrict these variations

in satisfying the required construction criteria. For facing bricks, dimensional

control is more stringent for wall appearance and lesser for other applications. Most

standards specify dimensional tolerances according to the types of masonry

construction.

There are two approaches of measuring dimensional tolerances in standards,

namely the individual and cumulative dimension of a set of bricks. In the recent

European Standard dimensional tolerance are specified in terms of the mean and the

range from a sample of 10 bricks and this should be within the range defined in the

specified categories. The dimensional tolerance determined from cumulative

dimensions of a set of bricks as given by Australian Standard AS 1225:1984,

Malaysian Standard MS 76 Part 2:1972 and British Standard BS 3921:1985 helps to

offset the individual brick dimensional variation, which maybe useful in determining

variation within and between batches of bricks delivered on site.

Efflorescence, that appear on the surfaces of bricks after construction, is

usually not harmful to a masonry structure but unsightly in facing brickwork. These

white stains indicate the presence of soluble salts in bricks. The test method for

efflorescence in all standards involves simple laboratory works and measurements

and evaluations of efflorescence are based on visual inspection. The test seems not

related to the field exposure that a brick is exposed to in a masonry structure.

Furthermore, with the introduction of limits for soluble salt content in all bricks, the

efflorescence requirement was considered as unnecessary and had been omitted by

the British Standard and the new European standard. However, this test is being used

by manufacturers to indicate the soluble salt content in bricks and its liability to

efflorescence.

53

Recent global development in standardisation works particularly in Europe

has brought about some significant changes to masonry standards. The British

Standard, upon which the existing Malaysian standard is based on, will soon be

replaced by the harmonised European Standard prEN 771-1 specifications for

masonry units. The new standard introduces some modifications to the BS 3921,

which include new test methods and requirements criteria, prompted by research

discovery and new technological development in masonry. A study on the

performance of local bricks is therefore timely to provide comprehensive

information on bricks considered relevant to the current construction industry and

market and design requirements pertaining to modern construction.

CHAPTER 3

LABORATORY TESTS ON PHYSICAL

PROPERTIES OF BRICKS

3.1 Introduction

This chapter examines the physical properties of the bricks. Laboratory

investigations were performed on samples of bricks at the Structural Laboratory of

the Faculty of Civil Engineering, Universiti Teknologi Malaysia. Tests were

conducted to examine dimensional tolerance, density, initial rate of suction, water

absorption, compressive strength, soluble salt content and efflorescence.

3.2 Sampling of Bricks

Sampling is a process involving the collection of bricks at random to make

up a sample to represent the population of bricks used in this research. The number

of specimens in a sample i.e. the size of sample (n) is the number of bricks required

for any tests. Sampling was carried out at a brick factory, which is considered a

major producer of brick in the country. The factory has a monthly production

capacity of 10,000,000 units of bricks and it is also a major exporter of bricks to

counties in Asia like Japan and Singapore.

55

Two categories of bricks comprising of the facing brick and the common

brick were sampled at random from the factory output. Facing bricks are quality

bricks with attractive external appearance and common bricks are meant for general

building works that do not require external look. Random selection means that every

brick must have a probability of being selected. However, this was found to be quite

impossible at times when bricks were in big piles making it difficult to reach and

acquired. Four factory visits were made and for each visit a batch of approximately

100 pieces of facing bricks and 40 pieces common bricks were selected. A batch is a

collection of bricks acquired at every visit.

3.3 Testing Programme

The testing programme (Table 3.1) shows the extent of the work detailing the

total number of batches used for the laboratory investigations including the number

of samples in every batch for the various tests. The test procedures and the sample

size (n), i.e. number of bricks required in every sample for testing of dimensional

tolerance of 24 bricks, Initial rate of suction (IRS), absorption, compressive strength,

soluble salt content and efflorescence were generally in accordance to BS 3921:

British Standard Specifications for Clay bricks (1985), with the exception of the

density test which were done with reference to the AS/NZS 4456.8:1997.

The tests were performed in sequence as shown in Figure 3.1, such that it

will optimise the quantity of sample used in the investigation. For example, each test

will commence with dimensional measurements, and the same 10 bricks be tested

for density, IRS, absorption and compression. The fragments from the compressive

strength will then be used for testing of soluble salt content. The efflorescence test

was conducted separately on another 10 bricks from each batch of samples.

The series of tests shown in Figure 3.1 were performed for the facing bricks,

which are referred to as structural bricks. The common bricks were only tested for

their compressive strengths. Structural bricks entailed design calculation which

requires the compressive strengths of units to be known, for this reason, it is

56

essential to examine the strengths characteristics and other physical properties.

Hence, the properties of facing bricks need to be investigated in this case. On the

other hand, common bricks, which are meant for general building works do not

require specification on the properties except for its compressive strength. Thus,

they are only tested for this particular property. Compressive strength test was

carried out on common bricks to examine the variation of strengths in order to

categorise the brick into their strengths classification. Efflorescence, which tends to

affect external appearance may be considered insignificant for common bricks as

they are usually used for infill walls with plastered surfaces. The water absorption

property may also not be considered essential in this case since the plaster may help

in resisting water penetration into a wall to a certain degree.

24 bricks 10 bricks 10 bricks Figure 3.1: Sequence of testing

Dimension Efflorescence

Density

Initial rate of suction

Absorption

Compressive strength

Soluble salt content

57

Table 3.1: Testing programme Number of samples per batch for the various tests

Dimensional tolerance

Bat

ch

Dat

e of

sa

mpl

ing

Num

ber

of

bric

ks

sam

pled

in a

ba

tch Overall

dimension (n = 24)

Individual dimensions (n = 6)

Density (n = 10)

Initial rate of suction (n = 10)

Water Absorption (n = 10)

Compressive strength (n = 10)

Soluble salt content (n = 10)

Efflores- cence (n = 10)

1 26/4/2001 100 facing bricks

2 8

3 3 3 6 2 1

40 common bricks

- - - - - 3 - -


4 16 8 8 8 8 3 1

40 common bricks

- - - - - 3 - -


4 16 8 8 8 8 4 1

40 common bricks

- - - - - 3 - -


4 16 8 8 8 8 3 1

40 common bricks

- - - - - 3 - -

Total samples for all batches 14 56 27 27 27 30 12 12 4

58 3.4 Dimensional Tolerance

Dimensional tolerances were measured from the respective length, width and

height of overall dimension of 24 bricks and individual brick dimension. Tests were

conducted on 24 bricks to examine the dimensional tolerance in accordance to BS

3921. The 24 bricks were selected at random from a batch of 100 bricks. For the

measurement of overall lengths, the bricks were placed in two rows, each of 12

numbers, on a flat surface in the laboratory. Measurements were made using an

inextensible steel tape. The measurements for the two rows were added to give the

overall dimension of length for 24 bricks. Measurements of width and height were

taken for 24 bricks in a row. A long steel channel, aligned against the row of bricks

ensured that bricks were arranged in a straight line (Figure 3.2). For individual

dimensions the vernier calliper were used in which a measurement to two decimal

places was recorded. The results for the overall dimension of length, width and

height are shown in Table 3.2. Table 3.3 shows the individual dimension for length

width and height in the samples. The complete tabulation of results for the

individual dimensions in each specimen is shown in Appendix A1.

Table 3.2: Overall dimensions of 24 bricks

Sample Length (mm)

Width (mm)

Height (mm)

1 5240 2415 1638 Batch

1 2 5254 2410 1646 3 5216 2408 1648 4 5263 2426 1651 5 5241 2421 1650

Batch 2

6 5243 2419 1653 7 5175 2405 1628 8 5218 2412 1640 9 5185 2413 1625

Batch 3

10 5178 2397 1634 11 5203 2416 1638 12 5211 2400 1643 13 5210 2409 1643

Batch 4

14 5213 2414 1644

59 Table 3.3: Individual brick measurement of length, width, and height for all batches

Sample Length (mm) Width (mm) Height (mm)

1 218.43 100.20 67.08 2 218.43 99.79 67.23 3 216.58 99.00 67.45 4 218.03 99.63 67.19 5 216.57 98.96 66.37 6 217.68 99.81 67.16 7 217.68 99.97 67.91

Batch 1

8 219.08 99.91 68.01 9 216.64 99.93 68.18

10 215.53 99.31 67.83 11 216.13 99.33 68.06 12 216.35 98.85 67.67 13 218.01 100.41 68.18 14 217.67 100.27 67.25 15 217.68 99.83 67.67 16 218.82 100.73 68.81 17 216.78 99.77 67.60 18 218.97 100.89 68.95 19 216.66 99.76 68.18 20 217.74 100.22 68.10 21 219.05 100.22 68.08 22 217.49 101.03 68.57 23 216.29 99.81 67.86

Batch 2

24 217.97 99.97 67.89 25 215.74 99.73 67.80 26 214.62 99.53 66.93 27 215.09 99.81 67.09 28 214.67 99.90 67.08 29 215.43 99.67 67.43 30 216.26 100.45 67.67 31 214.71 99.38 67.37 32 215.71 100.27 67.54 33 215.19 99.39 67.35 34 215.45 99.99 67.23 35 215.13 99.03 66.93 36 215.10 98.70 67.05 37 216.06 99.82 67.04 38 214.98 99.22 66.83 39 214.77 99.59 66.96

Batch 3

40 215.18 100.17 67.08 41 216.42 100.23 67.70 42 216.23 99.78 67.53 43 215.63 99.63 67.41 44 215.09 98.89 67.13 45 215.09 98.73 67.28 46 215.69 99.43 67.43 47 215.72 99.13 66.58 48 216.18 99.15 67.58 49 216.92 100.23 67.35 50 214.57 99.01 67.03 51 216.83 100.03 67.53 52 217.00 99.73 67.01 53 215.83 99.96 68.28 54 215.36 99.48 67.19 55 216.14 100.27 67.43

Batch 4

56 216.28 99.80 67.46 Mean x

Std. dev. s 216.42 1.912

99.73 1.116

67.48 0.888

60

(a)

(b)

(c)

Figure 3.2: Overall Measurement of (a) length, (b) width

and (c) height for 24 bricks

61 3.5 Density

The bricks density was measured in accordance to AS/NZS 4456.8, since BS

3921 does not provide for such testing specification. However, this is a new

requirements in the European Standard for which bricks are to be tested. Ten bricks

were selected from the 24 bricks used for dimensional testing. Each brick was

labelled with numbers for example 51, 27, 48…99 (Table 3.4) using permanent

waterproof ink for identifications. The weight of each brick was taken to represent

the ambient mass i.e. the mass at the time of measurement, mo. The bricks were then

immersed in water for 2 hours, then removed from the water and allowed to drain

for not more than 1 min. Any excess water on the surface were then removed by

wiping with a cloth. The brick was then weighed and the mass recorded i.e. m1.

After that, the brick was placed in an apparatus to measure its submerged mass, m2.

These procedures were repeated for all 10 bricks.

The device used to measure submerged mass of bricks throughout the testing

programme is shown in Figure 3.3. This device was an existing unit used previously

for measuring the density of concrete cubes in the laboratory. It consists of a water

bath and an attached steel cage to hold the specimens under investigations. The steel

cage is connected to a digital weight indicator. Upon lowering the cage and

specimen, the readings of submerged mass will be indicated by the digital indicator.

Based on Archimedes principle the submerged mass were used to evaluate the

volume.

Volume was calculated using submerged mass as stated in equation 3.1.

( )1 2(mm ) 1000V m m= − ×3

…(3.1)

Where,

1m = mass of wet brick in gram.

2m = submerged mass of brick in gram.

The volume is then used to calculate the ambient density Da using equation 3.2.

3( ) 1000000 in kg/moa

mDensity DV

= × …(3.2)

62 Where,

om = ambient mass in gram.

An example of the test results for density determined for bricks of Batch 1 is

shown in Table 3.4. A complete tabulation of results for tests carried out throughout

the research is given in Appendix A2.

Table 3.4: Density of bricks for Batch 1 Brick Identification

Ambient mass

0( )m gm.

Mass after 2 hours soaking

1( )m gm.

Immersed mass

2( )m gm.

Volume (V) V=(m1-m2)*1000

mm3

Density (Da) (mo/V)*1,000,000

kg/m3

51 2395 2630 1270 1360000 1761.03 27 2440 2590 1270 1320000 1848.48 48 2400 2620 1270 1350000 1777.78 67 2435 2650 1300 1350000 1803.70 32 2390 2630 1280 1350000 1770.37 6 2395 2600 1260 1340000 1787.31

19 2335 2470 1220 1250000 1868.00 22 2410 2610 1260 1350000 1785.19 50 2475 2690 1310 1380000 1793.48

Sam

ple

1

9 2365 2600 1250 1350000 1751.85 Mean x = 1794.719

Std. dev. s = 37.03036 2435 2690 1300 1390000 1751.80 44 2455 2640 1280 1360000 1805.15 43 2325 2570 1240 1330000 1748.12 64 2460 2670 1300 1370000 1795.62 38 2400 2600 1270 1330000 1804.51 45 2450 2680 1300 1380000 1775.36 62 2455 2670 1300 1370000 1791.97 30 2355 2560 1250 1310000 1797.71 70 2440 2620 1290 1330000 1834.59

Sam

ple

2

66 2430 2630 1280 1350000 1800.00 Mean x = 1790.483 Std. dev. s = 25.923

85 2315 2520 1230 1290000 1794.57 92 2305 2530 1230 1300000 1773.08 41 2390 2680 1250 1430000 1671.33 96 2510 2770 1350 1420000 1767.61 87 2420 2650 1300 1350000 1792.59 43 2385 2680 1290 1390000 1715.83 91 2270 2490 1200 1290000 1759.69 42 2420 2640 1290 1350000 1792.59 81 2465 2690 1330 1360000 1812.50 99 2405 2650 1310 1340000 1794.78

Sam

ple

3

Mean x = 1767.456 Std. dev. s = 43.169

63

Figure 3.3: Apparatus for the measurement of density


The bricks used for density tests were retested for the initial rate of suction.

Initially the bricks were dried in a ventilated oven for two and a half days at a

temperature of 110 °C. In accordance to BS 3921 constant mass is assured if bricks

are subjected to heating at 110 °C for not less than 48 hours. The bricks were

removed from the oven and cool to room temperature for a period of approximately

4 hours. Cooling was assisted by passing air over the bricks using an electric fan for

a period of 2 hours. Upon cooling, the bricks were weighed and the dry mass dm

recorded.

In the tests a large shallow rectangular pan of size 600mm × 600mm giving,

an area of 0.36m2 was used. Two 10mm steel bar were placed at the bottom of the

pan at approximately 100 mm apart, to form a platform for the bricks to rest during

measurement process (Figure 3.4). The steel bar was firstly immersed with water to

a depth of about 3mm. The pre-weighed dry brick was placed on the bar whilst the

water level is closely observed with a measuring gauge to ensure that depth of the

immersion for the brick was maintained at 3 ± 1mm throughout the duration of

immersion, 1 minute. After 1 minute, the brick was removed from the water and

excess water wiped off with a damp cloth. The brick was reweighed and the mass

64

wm recorded. These procedures were repeated for 10 bricks. Some typical results for

Batch 1 are shown in Table 3.5 and others can be found in Appendix A3. The initial

rate of suction due to gross area of immersion (IRSgross), in kg/m2.min is calculated

using equation 3.3a.

1000( )w dgross

gross

m mIRSA

−= …(3.3a)

Where,

dm is the mass of the dry brick in gram.

wm is the mass of the wet brick in gram.

Agross is the gross area of the immersed face of the brick in mm2.

The IRS for net area of immersion (IRSnet) was determined as shown in

equation 3.3b.

1000( )w d

netnet

m mIRSA

−= …(3.3b)

Where,

Anet is the net area of immersion i.e. gross area less the area of perforations.

Precautions were taken so that the limits of immersion remained at 3 ± 1mm

as required by BS 3921. The size of pan used in this testing programme was 0.36m2

in area and this did not cause a significant drop in water level after a subsequent test

was conducted at the immersion limits recommended by BS 3921. The minimum

size of the tank recommended by AS/NZS 4456 is 0.25m2.

The role of the pan size here is not considered very significant, for as long as

the tests were conducted in accordance to the depth of immersion and the duration of

absorption (1 min.). The larger the pan, the smaller the drop in water level and the

less frequent to top up the level to 3 ± 1mm limit. The BS 3921 does not specify the

size of the pan. ASTM C67 specifies that pan should be at least 0.19 m2.

Additionally, the Brick Institute of America through its Technical Note 39,

recommended a pan size of 0.19m2 and observations on bricks with IRS

40g/min./30in.2, equivalent to 2.05 kg/min.m.2, only caused a water level drop of

less than 0.25mm. In this regards, this is hardly measurable.

65

Figure 3.4: Apparatus for measuring the initial rate of suction

Table 3.5: Initial rate of suction in samples for Batch 1

Bri

ck

iden

tific

a Dry mass,

dm (gm)

Wetmass

wm (gm)

Length (mm)

Width (mm)

Immersed area, Agross (mm2)

IRSgross (kg/m2.min)

( )1000 w dm mA−

Immersed area, Anet (mm2)

IRSnet (kg/m2.min)

( )1000 w dm mA−

16 2445 2485 221.15 100.75 22280.86 1.795 18905.86 2.116 2 2390 2420 216.50 98.80 21390.20 1.403 18015.20 1.665

11 2415 2450 218.30 99.70 21764.51 1.608 18389.51 1.903 4 2370 2400 216.05 98.30 21237.72 1.413 17862.72 1.679 9 2435 2485 221.45 102.25 22643.26 2.208 19268.26 2.595

17 2430 2465 220.05 100.75 22170.04 1.579 18795.04 1.862 19 2440 2490 220.10 100.10 22032.01 2.269 18657.01 2.680 3 2435 2455 217.55 98.80 21493.94 0.930 18118.94 1.104 7 2415 2450 217.10 100.00 21710.00 1.612 18335.00 1.909

Sam

ple

1

8 2410 2435 216.60 99.80 21616.68 1.157 18241.68 1.370 1 2380 2410 216.55 99.55 21557.55 1.392 18182.55 1.650

12 2420 2455 217.95 99.75 21740.51 1.610 18365.51 1.906 10 2485 2515 218.60 99.65 21783.49 1.377 18408.49 1.630 18 2430 2450 216.30 97.95 21186.59 0.944 17811.59 1.123 6 2410 2445 217.00 99.80 21656.60 1.616 18281.60 1.914

15 2465 2500 216.30 99.15 21446.15 1.632 18071.15 1.937 5 2460 2490 217.50 99.65 21673.88 1.384 18298.88 1.639

20 2410 2435 217.50 99.15 21565.13 1.159 18190.13 1.374 14 2370 2400 217.75 99.65 21698.79 1.383 18323.79 1.637

Sam

ple

2

13 2370 2410 217.50 99.90 21728.25 1.841 18353.25 2.179 35 2410 2440 217.30 99.20 21556.16 1.39 18181.16 1.650 69 2420 2455 217.35 99.70 21669.80 1.62 18294.80 1.913 63 2435 2490 216.95 99.25 21532.29 2.55 18157.29 3.029 37 2400 2425 216.40 99.25 21477.70 1.16 18102.70 1.381 68 2430 2470 208.50 101.20 21100.20 1.90 17725.20 2.257 40 2410 2445 217.00 99.25 21537.25 1.63 18162.25 1.927 29 2410 2445 217.25 99.65 21648.96 1.62 18273.96 1.915 41 2415 2450 217.10 99.60 21623.16 1.62 18248.16 1.918 71 2440 2485 218.10 100.05 21820.91 2.06 18445.91 2.440

Sam

ple

3

39 2440 2475 216.95 99.35 21553.98 1.62 18178.98 1.925

66 3.7 Water Absorption (5-hours boiling test)

The same 10 bricks used for initial rate of suction tests were used for water

absorption test. The dry mass dm , were as recorded earlier in the initial rate of

suction test.

A large urn was used to accommodate two sets of samples comprising of 20

bricks (Figure 3.5). The bricks arranged in two tiers with spaces in between bricks

and tiers, were boiled for 5 hours and then allowed to cool naturally in the water for

about 18 hours. A minimum of 16 hours and a maximum of 19 hours of cooling

period were recommended by BS 3921. Each brick was weighed and the saturated

mass sm , recorded. Water absorption W, in percentage was calculated using the

following equation 3.4.

( )% 100 s d

d

m mWm−

= …(3.4)

Where,

dm is the dry mass

sm is the saturated mass

The experimental results for Batch.1 were shown in Table 3.6. Detailed

results for other bricks can be found in the Appendix A4.

Figure 3.5: Apparatus for water absorption test

67

Table 3.6: Water absorption of bricks for Batch 1 Brick identification

Dry mass

dm (gm) Saturated mass

sm (gm) W (Water absorption)%

( )100 s d

d

m mm−

7 2415 2670 10.559 5 2460 2710 10.163 1 2380 2640 10.924 13 2370 2670 12.658 8 2410 2640 9.544 14 2370 2645 11.603 4 2370 2625 10.759 20 2410 2665 10.581 19 2440 2775 13.730

Sam

ple

1

10 2485 2745 10.463 Mean x = 11.098 Std. dev. s =1.248

2 2390 2590 8.37 9 2435 2760 13.35 11 2415 2665 10.35 3 2435 2650 8.83 15 2465 2700 9.53 17 2430 2720 11.93 12 2420 2675 10.54 18 2430 2625 8.02 6 2410 2690 11.62

Sam

ple

2

16 2445 2740 12.07 Mean x =10.461

Std. dev. s =1.772 39 2440 2695 10.45 69 2420 2685 10.95 35 2410 2680 11.20 41 2415 2695 11.59 37 2400 2655 10.63 29 2410 2685 11.41 40 2410 2670 10.79 68 2430 2745 12.96 63 2435 2735 12.32

Sam

ple

3

71 2440 2710 11.07 Mean x =11.337

Std. dev. s =0.248


The bricks were tested for their compressive strength by imposing the bricks

to compression load until failure. The compressive machine used in the laboratory

was the Tonipact, with a capacity of 3000 kN. The machine was calibrated at the

early stage of the duration of the study.

68 In this work a study on the effects of compressive strengths of facing bricks

if tested in different orientations i.e. on its bed, stretcher and header face (Figure 3.7)

were conducted. Common bricks were only tested on their bed face.

Compressive strength tests were carried out on the same bricks after the

absorption test. Thus, the bricks were assumed to be fully saturated resulting from

the 5-hour boiling. To reduce friction caused by irregularities of the surface of the

bricks to be loaded, the bricks, placed in the machine were packed between two

pieces of plywood sheets, cut about 10mm bigger all round than the dimensions of

the brick. A fresh piece of plywood was used for every test.

In the test procedure, British Standard specifies that the rate of loading can

be gradually increased at a convenient rate not exceeding 35 N/mm2 until half of the

anticipated maximum load. Thereafter, the rate could be smoothly reduced to 15

N/mm2 and this rate to be maintained until failure. Although a higher rate of loading

could be used before half of the expected failure load, a constant rate of 15 N/mm2

were applied throughout the test in this work. A higher rate of loading was allowed

merely to reduce the time of testing and it is explained in the BS that higher rate of

loading at this stage has no influence on the ultimate strength. Therefore, a constant

rate of loading of 15 N/mm2 used throughout the test was justifiable. At failure the

brick collapsed and the machine stopped automatically. The maximum load was

recorded and the strength calculated by dividing the maximum load with the area of

the face subjected to loading i.e. bed face (length × width), stretcher face (length ×

height) or the header face (width × height). These areas used in the calculation were

based on the smaller of the two opposite faces.

Some typical results of compressive strengths of common bricks and facing

bricks for Batch. 1 are shown in Table 3.7 and 3.8 respectively. Example of results

for bricks tested on the stretcher face and header face are shown in Table 3.9 and

3.10 respectively. The complete results for compressive strengths are shown in

Appendix A5

69

Figure 3.6: Compressive machine -Tonipact 3000

Figure 3.7 a: Bricks tested on bed face

Figure 3.7 b: Bricks tested on stretcher face

70

Figure 3.7 c: Bricks tested on header face

Table 3.7: Compressive strength of common bricks for Batch 1 tested on bed

face

Length (mm)

Width (mm)

Area 1 (mm2)

Length (mm)

Width (mm)

Area 2 (mm2)

Smaller area

(mm2)

Maximum load Kn.

Compressive Strength N/mm2

216.10 99.25 21447.93 216.20 99.50 21511.90 21447.93 825.30 38.48 215.90 97.45 21039.46 215.50 97.45 21000.48 21000.48 829.30 39.49 217.50 100.05 21760.88 217.45 100.25 21799.36 21760.88 631.30 29.01 218.55 99.15 21669.23 219.05 99.95 21894.05 21669.23 866.30 39.98 217.85 98.95 21556.26 217.70 101.45 22085.67 21556.26 671.30 31.14 217.25 100.80 21898.80 217.25 101.20 21985.70 21898.80 791.30 36.13 217.95 99.65 21718.72 217.70 100.25 21824.43 21718.72 546.30 25.15 219.20 101.25 22194.00 219.25 100.40 22012.70 22012.70 866.30 39.35 218.80 100.85 22065.98 219.45 101.20 22208.34 22065.98 613.30 27.79

Sam

ple

1

219.00 100.65 22042.35 219.50 101.50 22279.25 22042.35 750.30 34.04 Mean x = 34.06

Std. dev. s = 5.47 214.75 100.00 21475.00 215.70 99.75 21516.07 21475.00 850.0 39.58 214.25 100.75 21585.69 213.85 100.00 21385 21385 813.0 38.02 215.50 100.80 21722.40 215.55 100.75 21716.663 21716.66 783.0 36.05 214.55 100.25 21508.63 215.50 99.45 21431.475 21431.48 582.0 27.16 214.9 100.75 21651.17 215.10 100.70 21660.57 21651.18 855.0 39.49 216.55 100.75 21817.41 216.25 100.95 21830.438 21817.41 730.0 33.46 216.00 100.25 21654.00 216.45 101.00 21861.45 21654 543.0 25.08 216.25 100.50 21733.12 216.15 100.15 21647.423 21647.42 786.0 36.31 216.20 100.75 21782.15 216.25 101.45 21938.563 21782.15 745.0 34.20

Sam

ple

2

215.70 100.40 21656.28 215.50 99.90 21528.45 21528.45 695.0 32.29 Mean x = 34.16

Std. dev. s = 4.90

71

Table 3.7 (cont.) 216.20 99.05 21414.61 216.20 99.35 21479.47 21414.61 830.00 38.76 215.90 97.00 20942.30 215.50 97.45 21000.48 20942.30 790.00 37.72 216.50 100.25 21704.13 217.45 100.30 21810.24 21704.13 636.00 29.30 217.75 99.25 21611.69 219.05 99.95 21894.05 21611.69 840.00 38.87 217.85 98.35 21425.55 217.70 101.25 22042.13 21425.55 567.00 26.46 217.35 100.20 21778.47 217.25 101.20 21985.70 21778.47 794.00 36.46 218.20 99.15 21634.53 217.70 100.25 21824.43 21634.53 543.00 25.10 218.75 101.05 22104.69 219.25 100.40 22012.70 22012.70 833.00 37.84 218.80 100.85 22065.98 219.45 101.20 22208.34 22065.98 614.00 27.83

Sam

ple

3

219.00 100.65 22042.35 219.50 101.50 22279.25 22042.35 749.00 33.98 Mean x = 33.23

Std. dev. s = 5.49

Table 3. 8: Compressive strength of facing bricks for Batch. 1 tested on the

bed face

Length (mm)

Width (mm)

Area 1 (mm2)

Length (mm)

Width (mm)

Area 2 (mm2)

Smaller area

(mm2)

Maximum load Kn.


216.10 98.50 21285.85 216.20 98.50 21295.70 21285.85 894.10 42.00 212.85 100.00 21285.00 217.85 99.90 21763.22 21285.00 988.80 46.46 217.75 99.35 21633.46 217.90 99.65 21713.74 21633.46 944.90 43.68 218.95 99.95 21884.05 218.75 99.65 21798.44 21798.44 1036.90 47.57 219.50 100.55 22070.73 219.40 100.75 22104.55 22070.73 840.90 38.10 217.25 99.40 21594.65 217.10 99.85 21677.44 21594.65 820.90 38.01 219.50 100.25 22004.88 220.10 100.20 22054.02 22004.88 776.90 35.31 217.20 99.80 21676.56 217.45 99.65 21668.89 21668.89 913.90 42.18 215.20 97.60 21003.52 215.55 98.20 21167.01 21003.52 694.90 33.08

Sam

ple

1

216.60 98.70 21378.42 216.30 98.65 21338.00 21338.00 844.90 39.60 Mean x = 40.60

Std. dev. s = 4.66 217.05 100.50 21813.53 218.15 100.75 21978.61 21813.53 1064.30 48.79 219.25 101.00 22144.25 219.50 101.10 22191.45 22144.25 957.30 43.23 217.30 99.50 21621.35 217.35 99.45 21615.46 21615.46 964.30 44.61 219.90 101.45 22308.86 220.50 101.35 22347.68 22308.86 977.00 43.79 217.50 99.85 21717.38 217.05 100.05 21715.85 21715.85 1091.90 50.28 217.55 99.10 21559.21 217.70 99.00 21552.30 21552.30 1106.00 51.32 216.95 99.25 21532.29 217.00 99.15 21515.55 21515.55 1113.00 51.73 217.50 99.55 21652.13 217.10 99.50 21601.45 21601.45 1187.00 54.95 217.00 100.00 21700.00 217.20 99.85 21687.42 21687.42 965.00 44.50

Sam

ple

2

217.00 99.40 21569.80 216.45 99.25 21482.66 21482.66 1159.90 53.99 Mean x = 48.72 Std. dev. s = 4.40

72 Table 3. 9: Compressive strength of facing bricks tested on the stretcher face

Length (mm)

Width (mm)

Area 1 (mm2)

Length (mm)

Width (mm)

Area 2 (mm2)

Smaller area

(mm2)

Maximum load (Kn.)


218.00 67.50 14715.00 214.90 67.45 14495.01 14495.01 570.00 39.32 217.00 67.30 14604.10 216.50 66.75 14451.38 14451.38 569.00 39.37 217.55 64.50 14031.98 217.30 64.50 14015.85 14015.85 488.00 34.82 217.25 67.75 14718.69 217.00 68.00 14756.00 14718.69 573.00 38.93 217.10 68.35 14838.79 217.15 68.00 14766.20 14766.20 581.00 39.35 217.95 66.90 14580.86 217.50 67.00 14572.50 14572.50 540.00 37.06 216.85 67.30 14594.01 216.85 68.00 14745.80 14594.01 538.00 36.86 218.00 67.10 14627.80 217.65 66.00 14364.90 14364.90 529.00 36.83 216.50 67.90 14700.35 216.50 68.00 14722.00 14700.35 544.00 37.01

Sam

ple

1

217.70 67.75 14749.18 217.00 67.75 14701.75 14701.75 490.00 33.33

Table 3.10: Compressive strength of facing bricks tested on the header face

Length (mm)

Width (mm)

Area 1 (mm2)

Length (mm)

Width (mm)

Area 2 (mm2)

Smaller area (mm2)

Maximum load (Kn.)


101.10 68.95 6970.85 101.55 68.42 6948.05 6948.05 18.50 2.66 99.65 68.05 6781.18 99.91 68.00 6793.88 6781.18 27.00 3.98

100.85 67.25 6782.16 100.65 67.00 6743.55 6743.55 23.60 3.50 100.10 67.85 6791.79 100.15 67.77 6787.17 6787.17 26.70 3.93 100.00 68.75 6875.00 99.95 68.30 6826.59 6826.59 15.60 2.29 98.55 67.95 6696.47 97.25 67.55 6569.24 6569.24 29.70 4.52

100.15 67.30 6740.10 100.25 67.85 6801.96 6740.10 24.30 3.61 100.10 68.20 6826.82 99.85 68.25 6814.76 6814.76 20.80 3.05 96.45 67.70 6529.67 98.55 68.05 6706.33 6529.67 27.90 4.27

Sam

ple

2

98.60 67.95 6699.87 99.00 68.30 6761.70 6699.87 28.40 4.24

3.9 Soluble Salt Content

Fragments of 10 bricks from the compressive strength test were randomly

selected to represent the exterior and interior of the bricks to make up the sample for

tests on soluble salts content. The sample was prepared by the crushing method as

given in BS : 3921 1985. About 25 gm. of ground brick passing sieve size 150 µm.

were then collected as the sample and dried in the oven at 110 °C.

73

The chemical test to determine the soluble salt content was carried out in the

laboratory of the Science Faculty of the Universiti Teknologi Malaysia. The soluble

salt comprises of water-soluble salts of calcium, magnesium, sodium and potassium

and acid-soluble sulphate. The acid-soluble sulphate was extracted in accordance to

the methods found in BS 3921 Appendix B.3.1 and the water-soluble salts,

Appendix B.4.1.

Sulphate was determined by the gravimetric method as described in BS

3921, Appendix B.3.2.2. In this traditional analytical process sulphate was

precipitated, filtered, and finally burned in a crucible. The mass of the acid soluble

sulphate M in gram was determined using equation 3.5 (BS 3921:1985). Results

showing the percentage of sulphates present in the various samples are shown in

Table 3.11.

( )1 00.4115= −M m m …(3.5)

Where,

0m is the mass of the crucible in gm.

1m is the mass of the crucible and burnt precipitate and paper in gm.

Table 3.11: Percentage of sulphate content in the samples from all batches

Sample

Mass of precipitate in gm. ( )1 0m m−

Mass of sample, W

Mass of sulphate ( )1 00.4115M m m= −

Percentage of sulphate in sample

100%MW

×

1 0.0049 2.6889 0.00202 0.07

Batch 1 2 0.0045 2.5288 0.00185 0.07 1 0.0056 2.4917 0.0023 0.09 2 0.0031 2.0387 0.00128 0.06

Batch 2

3 0.0045 2.0255 0.00185 0.09 1 0.0010 2.0315 0.00041 0.02 2 0.0043 2.0224 0.00177 0.09 3 0.0020 2.0224 0.00082 0.04

Batch 3

4 0.0010 2.0465 0.00041 0.02 1 0.0011 2.0819 0.00045 0.02 2 0.0009 2.0371 0.00037 0.02

Batch 4

3 0.0009 2.0072 0.00037 0.02

74

Calcium, magnesium, sodium and potassium were determined by the

instrumental method. The instrument used was the atomic absorption spectroscopy

(AAS) called GBC Avanta PGF 3000 Spectrometer. The AAS, which measures the

presence of metals in liquid samples works on the principal of atomising a sample

and quantitatively determining the concentration of atoms in the gas phase by

measuring the intensity of light absorbed. The schematic presentation of the process

is shown in Figure 3.8.

Flame

Light source

Sample

Atomizer-burnerMonochromator

Photomultiplier

Figure 3.8: A schematic diagram of an atomic absorption

spectrometer (Hammer, 1996)

Before testing the samples in the AAS, calibration curves for the salts of

calcium, magnesium, sodium and potassium were determined. This was carried out

by running standard solution, with known concentrations of the respective salts, on

the AAS and observing the absorbance readings from AAS (Table 3.12, 3.14 and

3.17). The salts concentrations (x) were plotted against the absorbance (y) to produce

calibration curves for each salt and the relationship between absorbance and

concentration were determined as shown by the equations in Figures 3.9, 3.10 and

3.11 for calcium, sodium and potassium and magnesium respectively.

Salts of calcium, sodium, potassium and magnesium were extracted from the

samples as given in Appendix B of BS 3921:1985. The filtrate from the samples was

run in the AAS which gave the readings of absorbance for each salts. Using the

equations from the calibration curves and with readings of the absorbance from

75 AAS, the concentration of the salts in the samples could be determined. Tables 3.13,

3.15, 3.16 and 3.18 show the corresponding percentage of calcium, potassium,

sodium and magnesium in the samples.

Table 3.12: Standard calibration data for calcium Sample label

Concentration mg/l

Mean Absorbance from AAS

Replicates

Blank 0.002 0.002 0.002 0.002

Standard 1 5 0.202 0.203 0.201 0.202

Standard 2 10 0.41 0.409 0.413 0.41

Standard 3 15 0.618 0.615 0.619 0.62

Standard 4 20 0.814 0.811 0.81 0.82

Standard 5 25 1.023 1.023 1.023 1.023

y = 0,0409x - 0,0004R2 = 0,9999

00,20,40,60,8

11,2

0 5 10 15 20 25 30Concentration,mg/l

Abs

orba

nce

Figure 3.9: Calibration curve for detection of calcium

76

Table 3. 13: Percentage of calcium in samples for all batches

Sample Absorbance from AAS,

y

Concentration, x 0.0004

0.0409yx +

=

mg/l

Volume of solution, v

mL

Weight of sample, w

gm.

Percentage of calcium in sample

6 10010

x vw

××

×

1 0.543 13.286 100.0 10.1117 0.013

Bat

ch 1

2 0.580 14.185 100.0 10.3982 0.014

1 0.122 3.013 100.0 10.1036 0.003

2 0.238 5.854 100.0 10.0147 0.006

Bat

ch 2

3 0.647 15.813 100.0 10.0549 0.016

1 0.414 10.147 100.0 10.0096 0.010

2 0.281 6.904 100.0 10.0337 0.007

3 0.450 11.023 100.0 10.0844 0.011 Bat

ch 3

4 0.284 6.977 100.0 10.0238 0.007

1 0.311 7.636 100.0 10.0161 0.008

2 0.390 9.562 100.0 10.0294 0.009

Bat

ch 4

3 0.420 10.293 100.0 10.0366 0.010

Table 3.14: Standard calibration for sodium and potassium

Sodium Potassium Sample

Label Concentration

mg/l Mean

Absorbance from AAS

Concentration mg/l

Mean Absorbance from AAS

Blank 0.004 0.002

Standard 1 1 0.222 2 0.172

Standard 2 2 0.44 4 0.338

Standard 3 3 0.681 6 0.514

Standard 4 4 0.887 8 0.682

Standard 5 5 1.099 10 0.865

77

y = 0,0865x - 0,0048R2 = 0,9998

y = 0,2201x + 0,0055R2 = 0,9993

0

0,2

0,4

0,6

0,8

1

1,2

0 2 4 6 8 10 12

Concentration Mg/lA

bsor

banc

e

Figure 3.10: Calibration curve for detection of sodium and potassium Table 3. 15: Percentage of potassium in samples for all batches


y


0.0865yx +

=

mg/l


mL

Weight of sample, w

gm.

Percentage of potassium in sample

6 10010

x vw

××

×

1 0.282 13.286 100.0 10.1117 0.003

Bat

ch 1

2 0.276 14.185 100.0 10.3982 0.003

1 0.549 3.013 100.0 10.1036 0.006

2 0.743 5.854 100.0 10.0147 0.009

Bat

ch 2

3 0.623 15.813 100.0 10.0549 0.007

1 0.297 10.147 100.0 10.0096 0.003

2 0.511 6.904 100.0 10.0337 0.006

3 0.399 11.023 100.0 10.0844 0.005 Bat

ch 3

4 0.290 6.977 100.0 10.0238 0.003

1 0.352 7.636 100.0 10.0161 0.004

2 0.356 9.562 100.0 10.0294 0.004

Bat

ch 4

3 0.367 10.293 100.0 10.0366 0.004

Potassium Sodium

78

Table 3. 16: Percentage of sodium in samples for all batches


y


0.2201yx −

=

mg/l


mL

Weight of sample, w

gm.

Percentage of sodium in sample

6 10010

x vw

××

×

1 0.587 2.642 100.0 10.1117 0.003

Bat

ch 1

2 0.427 1.915 100.0 10.3982 0.002

1 0.791 3.569 100.0 10.1036 0.004

2 0.546 2.456 100.0 10.0147 0.002

Bat

ch 2

3 0.564 2.537 100.0 10.0549 0.003

1 0.316 1.411 100.0 10.0096 0.001

2 0.574 2.583 100.0 10.0337 0.003

3 0.355 1.588 100.0 10.0844 0.002 Bat

ch 3

4 0.332 1.483 100.0 10.0238 0.001

1 0.538 2.419 100.0 10.0161 0.002

2 0.498 2.238 100.0 10.0294 0.002

Bat

ch 4

3 0.374 1.674 100.0 10.0366 0.002

Table 3.17: Standard calibration for magnesium Sample label

Concentration mg/l

Mean Absorbance from

AAS

Blank 0.001 Standard 1 1 0.176 Standard 2 2 0.349 Standard 3 3 0.514 Standard 4 4 0.701 Standard 5 5 0.887

y = 0,1774x - 0,0068R2 = 0,9993

0

0,2

0,4

0,6

0,8

1

0 1 2 3 4 5 6

Concentration mg/l

Abs

orba

nce

Figure 3.11: Calibration curve for detection of magnesium

79

Table 3. 18: Percentage of magnesium in samples for all batches


y


0.1774yx +

=

mg/l


mL

Weight of sample, w

gm.

Percentage of magnesium in

sample

6 10010

x vw

××

×

1 0.476 2.722 100.0 10.1117 0.003

Bat

ch 1

2 0.29 1.673 100.0 10.3982 0.002 1 0.428 2.451 100.0 10.1036 0.002 2 0.57 3.251 100.0 10.0147 0.003

Bat

ch 2

3 1.069 6.064 100.0 10.0549 0.006 1 0.694 3.950 100.0 10.0096 0.004 2 0.588 3.353 100.0 10.0337 0.003 3 0.747 4.249 100.0 10.0844 0.004 B

atch

3

4 0.573 3.268 100.0 10.0238 0.003 1 0.477 2.727 100.0 10.0161 0.003 2 0.513 2.930 100.0 10.0294 0.003

Bat

ch 4

3 0.832 4.728 100.0 10.0366 0.005

3.10 Efflorescence

Ten bricks were required for the efflorescence test. Each brick was covered

with plastic sheet around the three sides, leaving one side exposed to the atmosphere

(Figure 3.12). A wide mouth bottle filled with distilled water was then inverted on

top of this exposed surface for a duration of 48 hours. The bottle should always

contain water and toped up whenever necessary. After 48 hours, the bottle was

removed and the exposed surface left to dry for 9 days in the laboratory conditions.

A warm place in the laboratory with natural air circulating was selected for this

purpose. This procedure was repeated but for the second time a drying period of 16

days was allowed. After these cycles of wetting and drying the exposed surface of

each specimen was examined for efflorescence. Efflorescence was rated in

accordance to the bricks that showed maximum effects.

80

Figure 3.12: Efflorescence test

CHAPTER 4

STATISTICAL ANALYSIS OF TEST SPECIMENS

4.1 Introduction

This chapter presents the theoretical approaches to statistical calculations and

methods of sample analyses in deriving estimates of population representation.

4.2 General Approach for Analysing Samples

In principle, the processing of sample data involves several steps. The first

step is usually to describe data characteristics by showing its averages and

dispersion. Data could be represented graphically by the histograms and frequency

curve. Besides showing data distribution, the histogram and frequency curve

provides selection on the probability functions to be used as a mathematical model

in deducing the estimate of population mean from samples.

In a typical statistical analysis, before any estimates could be accepted,

results from samples have to be tested and this is referred to as hypothetical testing.

Quality control charts developed from normally distributed data could be regarded

as a form of hypothetical testing (BS 2846:Part 1:1991- Guide to statistical

interpretation of data). In this graphical form, a quick assessment could be made to

detect the homogeneity of data.

82

The analysis of variance (ANOVA) is another form of statistic hypothetical

testing. In an ANOVA, the F-test is carried out to test the null hypothesis (N.H.) of

no significance difference between variances in samples. From the ANOVA the

components of variance could be analysed and the best estimate of population

variance derived.

4.2.1 Description of Data

A group of observations or data is usually described by computing its

descriptive statistics comprising of its averages which include the mean, median and

mode and its dispersion, consisting of the standard deviation, variance and the range.

The sample mean shows the average value of data in a sample, given by

Equation 4.1 (Bland, 1985)

1Sample Mean = ni ix

xn=∑ …(4.1)

For a set of n values 1 2, ,... nx x x

Where,

x= the measurements or observations

n= the numbers of observations.

The median and the mode are also averages that described the sample. The

median in a set of data is the central observation, the values being ranked in order of

size. In other words, half of the data will have a value less than the median, and the

other half of the data will have a value greater than the median.

Mode is a value that occurs with the greatest frequency. A comparison of the

mean and median and mode can reveal information about skewness of the

distribution curve as illustrated in Figure 4.1.

83

The spread of the data or the dispersion can be measured by the standard

deviation, range, variance and the coefficient of variation (c.v.). These

measurements show the variation of each data from their mean. Variance and

standard deviation is computed using equation 4.2 and 4.3 respectively (Bland,

1985). The standard deviation for a sample is a square root of the variance and is

more often used to describe data. The standard deviation has an advantage over the

variance since it has the same unit as the variable tested. The c.v. given in equation

4.4 is a measurement of relative dispersion since it is given on a percentage basis.

Range (equation 4.5), is the difference between the highest and the lowest data. It is

a quick way of analysing data variation. However, its use is limited to small sample

only since it is obtained from two extreme values without giving consideration on

other data in the range.

The range and standard deviation are related so that for any given value of

observations n, an estimate of the standard deviation, estimates can be made from the

mean value of sample range R (equation 4.6).

( )2

2 1Sample variance, 1

n

ix x

sn

=

−

=−

∑ …(4.2)

( )2

1Sample standard deviation, = 1

n

ii

x xs

n=

−

−

∑ …(4.3)

Coefficient of variation, c.v. = 100 %sx× …(4.4)

Range, = max min i iR x x− …(4.5)

estimates R d= × (BS 2846: Part 1, 1991) …(4.6)

Where,

d is a coefficient based on the number of observations n, given in Appendix

B Table B3.

84

Figure 4.1: Mean, median and mode in a distribution

skewed to the right

4.2.2 Histograms and Normal Distribution Curve

Histograms are statistical graphs showing frequency of data where horizontal

axis and vertical axis represent the class interval (i) and the frequency respectively.

In a histogram, if the number of data were increases, the number of classes will

increase and subsequently the class widths decreases. As a result the histogram

approaches a smooth curve, thus called the frequency distribution curve.

Past observations revealed that most physical measurements could be

approximated to a normal distribution curve (Chatfield, 1979, Paradine and Rivettes,

1960); the approximation improves as number of variables increased. In virtue of the

central limit theorem, we can assume that data would eventually approach a normal

distribution for greater number of data. The normal distribution function also known

as normal probability density functions is given by equation 4.7 (Grimm, 1988).

1 2( ) (2 ) exp ( ) / 2f x x x sπ −= − − …(4.7)

Value of observation Mode

Median

Mean

Frequency

85

Where,

( )f x = normal probability density function for a sample. This refers to the

height of an ordinate at a distance x x− from the mean.

s = standard deviation of sample.

Equation 4.7 is transformed to the standard normal distribution function by

putting ( )z x x s= − as shown by equation 4.8 (Grimm, 1988).

( ) ( )1 2 2( ) 2 exp 2 f z zπ −= − …(4.8)

Where,

( )f z is the normal probability density function for a sample in terms of z.

The computed frequency illustrated in the form of a histogram is given by equation

4.9 (Grimm, 1988).

( )y ni f z s= …(4.9)

Where,

n= number of samples

i= number of units in a class interval

s= standard deviation of sample

The integration of equation 4.8 between any values of z produces the normal

probability function, i.e. the area under the curve between the stated values of z. The

area under the probability curve divided into hundred equal parts gives the percentile

values and a 33-percentile value divides the curve into three parts. Grimm (1988),

highlighted that values falling in the upper 33 percentile could be grouped as those

of high values. The lower 33 percentile are regarded as low values whilst normal

values are those lying in the middle third of the distribution.

4.2.3 Log-normal Distribution Curve

If distribution of data is skewed, where the mean, mode and median are not

coincident as in normal distribution then log normal distribution could be used. The

log-normal distribution is essentially the same as the normal, but with ln (x)

86

substituted for x. The log-normal has probability distribution function given by

equation 4.10. Grimm (1988) suggested that log-normal distribution is useful for

data with c.v. (ν ) exceeding 30%.

( )20.5 1 2( ) (2 ) ( ) exp ln / 2f x x xπ β α β− − = − − …(4.10)

( ) 0.52ln 1xα ν− = +

…(4.11)

s xν = …(4.12)

( ) 0.52ln 1β ν = + …(4.13)

Where,

( ) 1lnz x α β −= − …(4.14)

( )0.5 1 2( ) (2 ) exp 2f z z zπ β β α− − = − − − …(4.15)

( )y ni f z= …(4.16)

Where,

y = the histogram ordinate at any value of x in the histogram,

n = number of data in the histogram,

i = x interval in the histogram,

ν = c.v. in decimal.

An application of this statistical analysis will be demonstrated in section 4.3

for samples used in this research.

4.2.4 Derivation of Population Estimates

Assuming that data is normally distributed, therefore the functions of the

normal distribution curve could be used to derive estimates for the population.

For a normal distribution curve the integration of equation 4.8 of the normal

curve between specified limits is a probability function, which represents the area

87

under the normal curve. The full range of this probability function could be found in

statistical table. However, limits, which are of importance to this work is shown here

in Figure 4.2. From Figure 4.2 it can be seen that approximately 70 % of sample

data will lie within the area covered by a point on each side of the mean value,

denoted by one unit of standard deviation i.e.1σ . About 95 % will lie within the

area bounded by 1.96σ on each side of the mean and 99 % at 3.09σ from each side

of the mean. The distribution at 95 % probability is important in a production. It

provides a 95 % confidence that not more than 1 in 40 results would be below the

required specification limits. Therefore, a 95 % confidence of the population mean

can be estimated from sampling distribution using equation 4.17 (Bland, 1985).

1.96x s nµ = ± …(4.17)

Where,

µ = population mean

x = sample mean

s = sample standard deviation

n = sample size

Figure 4.2: Areas under normal probability curve

In virtue of the central limit theorem, the estimate is good on normally

distributed data with large samples size, i.e. n greater than 30 (Bland, 1985 and

Triola, 1989). If n is smaller than 30 the distribution of sample data will follow, the t

3413

%

3413

%

13.6

0%

13.6

0% 2.14% 2.14%

f(x), f(z)

x = -1σ x= -1.96σ x=1σ x=1.96σ x x= -3.09σ x= 3.09σ x= 0 z=-3.09 z=-1.96 z=-1 z=0 z=1 z=1.96 z=3.09 z

88

distribution and value of 1.96 from equation 4.7 will be replaced by ct (the

percentage point of the t distribution which can be obtained from Appendix B Table

B2). Thus, the population estimate of the mean (µ ) for a small sample is given by

equation 4.18 (Bland, 1985).

csx tn

µ = ± …(4.18)

The t-distribution, formulated by W.S. Gosset in 1908 has similar properties

to the normal distribution except that it has more spread about the mean as shown in

Figure 4.3. Another important feature of the t-distribution is that it has different

curves for different sample sizes. The t distribution depends on a parameter called

degrees of freedom (df) given by n-1, where n denotes the samples size.

(Mean)x

N orm al distribution

distribution w ith n=10t −

distribution w ith n=20t −

Figure 4.3: T-distribution curves for various values of n

(Chatfield, 1978)

The sample size in this research is smaller than 30, therefore, the t-

distribution was used in conjunction with equation 4.18 to arrive at the mean value

of the population. Example of these will be illustrated in section 4.3.4.

89

4.2.5 Hypothesis Testing

4.2.5.1 Analysis of Variance (ANOVA)

The analysis of variance (ANOVA) is a statistical tool developed from

normal distribution theory and is used for testing the significance difference of

several means. The ANOVA in testing a hypothesis that there is no difference in the

means between samples is called a single factor ANOVA.

A single factor ANOVA is accomplished by analysing the variance and by

partitioning the total variance into two, the component due to true random error i.e.

within samples ( withinMS ) and the component due to differences between means of

several samples ( betweenMS ). These two components are compared by means of an F-

test as shown in equation 4.19.

calc between withinF MS MS= …(4.19)

If calcF is smaller than the value of the critF given in statistical table of the F-

distribution (Appendix B Table B1), then the N.H. is accepted. This implies that

there is no significant difference between the means of the several samples and

within samples and therefore, the best estimate for the variance is the total variance

from within and between samples. On the other hand if calcF is larger than critF , then

the differences between the variance is considered significant. Therefore, the null

hypothesis of no differences between means is rejected and the alternative

hypothesis that the means are significantly different is accepted. Table 4.1 shows the

components of variance for the case when the N.H. is accepted or rejected.

90

Table 4.1: Components of variance from ANOVA Source of Variation

Sum of Squares

SS

Degrees of Freedom

df

Mean square MS

(2)÷(3)

When the N.H. is accepted the mean square is an estimate of

When the N.H. is rejected the mean square (MS) is an

estimate of (1) (2) (3) (4) (5) (6)

Between samples

betweenSS . 1No of samples − betweenSS df÷ 2σ 2 2

rcσ σ+ c= sample size

Within samples

withinSS

. Total specimensin samples No of

samples− withinSS df÷ 2σ 2σ

Total between

within

SSSS+

1

Total specimensin samples −

Total SSTotal df

÷ Best estimate of

2σ -

Referring to Table 4.1 of the ANOVA, when the N.H. is rejected, the mean

square (MS) is an estimate of 2 2rcσ σ+ . With c known i.e. size of sample and the

value of 2 2rcσ σ+ can be obtained from col. (4) of Table 4.1, 2

rσ the variance

between samples can be computed. This gives the new estimate of population

variance from the ANOVA as 2 2rσ σ+ (Loveday). In this study, the ANOVA was

particularly used to derive the best estimate for the variance between and within

samples in estimating the population means.

4.2.5.2 Control Charts

Control charts are graphical techniques used mainly to assess quality of a

production in an industry since it gives a rapid indication of the population quality

and enables appropriate action to be undertaken when necessary. A process is said to

be in control if there is no significant changes in the means and standard deviation.

Thus two control charts are required, one for monitoring the mean and the other one

for monitoring the variations. Examples of control charts for means and ranges are

as shown in Figures 4.4 and 4.5 respectively.

The three basic components of a control charts (Figure 4.4) are:

(i) A centre line, which represents the mean, for the respective mean or

range chart of samples.

91

(ii) Statistical control limits, i.e. the upper and lower action and warning

lines. These define the constraints for variations and if exceeded

shows that the process is out of control or data is not homogeneous.

(iii) Performance data plotted over time of production.

Two pairs of control limits are used. The first pair represents warning or

inner limits. These are set so that there is a 2.5 % probability (1 in 40) of a sample

mean having a value below the lower limit and a 2.5 % probability of its having a

value above the upper limit. The action or outer limits are set so that there is a

probability of 0.1 % (1 in 1000) of the mean falling above the upper limit and a

probability of 0.1 % of its falling below the lower limit. A process is said to be in

statistical control if only 1 out of 40 samples is found outside the warning lines and

1 out of 1000 samples outside the action lines.

Control charts could also be used to test homogeneity of data in samples (BS

2846: Part 1:1991- Guide to statistical interpretation of data). In terms of

homogeneity the occurrence of a single point outside 1 in 1000 control lines or of

more than one or two outside the 1 in 40 control lines is considered to be evidence

that data are not homogeneous.

The upper and lower warning and action lines for means are given by

equation 4.20 and 4.21.

Warning lines = 1.96 xx σ± …(4.20)

Action lines = 3.09 xx σ± …(4.21)

Where,

x = mean of sample means

xσ = standard deviation of mean

xsn

σ = …(4.22)

Where s is the estimate of the population standard deviation and n the sample size.

The value s is given in equation 4.6.

s Rd= …(4.23)

92

Hence, the warning limits for the mean (MWL)= 1.96Rdxn

± …(4.24)

Putting '0.025

1.96d An

= , the warning limit for the mean become

MWL = '0.025x A R± …(4.25)

Similarly the action limits for the mean (MAL) are

MAL = 3.09Rdxn

± …(4.26)

Putting '0.001

3.09d An

= , the action limits for the mean become

MAL = '0.001x A R± …(4.27)

In the range chart, warning (RWL) and action (RAL) lines are given by

equation 4.28, 4.29, 4.30 and 4.31 respectively (BS 2846: Part 1:1991).

The upper RWL = '0.025D R …(4.28)

The lower RWL = '0.975D R …(4.29)

The upper RAL = '0.001D R …(4.30)

The lower RAL = '0.999D R …(4.31)

The control limit factors ' ' for mean and for rangeA D can be obtained from

Appendix B, Table B4.

93

1 5

Sam

ple

mea

n

1 5

Sam

ple

rang

e

Figure 4.4: Control charts for sample means and ranges

(Neville, 1985)

4.3 Application of Statistical Methods for Samples Under Investigation

The statistical principles explained in section 4.2 were used throughout the

work for processing sample data. The statistical computations in this work were

facilitated by the computer software, Microsoft Excel 2000.

Mean

Upper warning line

Upper action line

Lower warning line

Lower action line

10 15 20 25 Sample Number

115

120

125

130

110

Mean

Upper warning line

Upper action line

Lower warning line Lower action line

10 15 20 25 Sample Number

5

10

15

20

0

94

An example of the application of these analyses is shown here with the

results of water absorption test. The statistical process as shown in Figure 4.5 is

described below:

i) First, the average and dispersion of data from samples in all batches

were determined through the computations of the descriptive

statistics consisting of the mean, median, mode, standard deviation,

range, and c.v. (Table 4.2).

ii) The distribution of data was shown graphically by plotting the

histogram. Assuming data to be normally distributed a normal curve

fit was computed (Table 4.4) and the normal curve superimposed on

the histogram as shown in Figure 4.6. Using the normal probability

function the 33-percentile values were determined to identify the

distribution of data for good, medium and low values corresponding

to the upper, middle and lower 33-percentile values.

iii) Control charts of samples means and ranges were plotted to check the

homogeneity of data. The data were examined for outliers i.e. data

not complying with control charts criteria for homogeneity and would

be regarded as not representing the population in the study and thus

ignored in the analysis of estimates.

iv) The F-test from ANOVA was performed to test the null hypothesis

that there was no significant difference between the variances in the

samples. From the ANOVA the components of variance were used to

derive estimate of population variance.

v) Lastly, estimates of population mean for small sample i.e. n< 30 at 95

% confidence were deduced using equation 4.18. Since the size of

samples i.e. number of specimens in a sample were less than 30 for

all the tests considered in this research therefore, equation 4.18 were

used throughout in this study.

95

Figure 4.5: Process of statistical analysis

Descriptive statistics

Mean Median Mode Standard deviation Range Coefficient. of variation

Histogram and frequency curve

ANOVA /F-test

Control charts

To test data homogeneity

To test significance of difference in the variance of samples

Deducing population estimates

Homogeneous

No significance difference in the variance

Non-homogeneous

Examine data for outliers

Components of variance

Significant

Data

Deriving estimates from normal probability function

Assuming data to be normally distributed

96

4.3.1 Description and Presentation of Sample Data

Water absorption in every specimen of bricks from samples in Batches 1, 2,

3 and 4 were determined and the descriptive statistics consisting of the mean,

median, mode, standard deviation, variance, range, and c.v. for all data were

computed and tabulated (Table 4.2).

The graphical presentation of data is shown by plotting the histogram and the

normal curve fit. To plot the histogram, data were grouped into 10 classes. In

accordance to BS 2849 (Guide to statistical interpretation of data), groupings could

consist of between 10 and 20 classes. Having decided on the number of classes, the

class intervals (i) were determined. From Table 4.2, the maximum value was 14.376

and the minimum was 7.655. The range (R) is the difference between the maximum

and the minimum. If there were 10 class intervals, there were about R/10 or 0.7 units

per class interval, i.e. i = 0.7. The frequency of data occurrence against these

selected class intervals could then be determined. Data frequency distribution is

given in Table 4.3 and its histogram plotted as shown in Figure 4.6. It could be

observed from the histogram that a few range of high values were located

approximately towards the centre of the distribution and smaller values tailing on

both sides from the centre, a typical feature of a normally distributed data.

Therefore, in virtue of the central limit theorem, with greater number of data it could

be assumed that the contour of the histogram would eventually approach a normal

curve.

Since data were assumed to be normally distributed a curve normalised to fit

in the distribution were constructed. In the construction of the normal curve, the

ordinates were computed at every midpoint of the intervals in the histogram using

equation 4.9. These ordinates as shown in column 5 of Table 4.4 were used to plot

the normal curve, which is superimposed on the histogram (Figure 4.6). From the

normal curve, it was seen that the values of the mean, median and mode did not

coincide meaning that it was skewed. In cases like this, Grimm (1988) suggested

that normal curve function could still be used for the probability analysis if the c.v.

of data in the samples does not exceed 30%.

97

Coefficient of variation was found to be 11.4 % which is less than 30 % and

therefore, in accordance to Grimm do not require a log-normal function for its

probability analysis. However, a log-normal curve was plotted to verify this theory

by Grimm. The ordinates for the log-normal curve were derived using equations

4.11 through equations 4.16.These ordinates as shown in column 8 of Table 4.4 were

used to plot the log-normal curve (Figure 4.6). It was found that it almost overlap

with the normal curve. Hence, this proved Grimm’s theory that a log-normal curve is

only useful for data with c.v. of more than 30%.

To enhance the application of this theory further, some verifications

regarding this application for a case of higher c.v. was felt necessary. Therefore,

results for compressive strength of common bricks having a c.v. of 25.4 %, was

computed for its log-normal curve. Table 4.5 shows the computed normal and log-

normal frequency at the midpoint of each interval in the histogram and with these

data, the normal and log-normal curves were drawn on the histogram (Figure 4.7). It

was found that there was a greater shift between these two curves. In order to check

the reliability of results, if probability is based on normal curve for such cases, the

33 percentile values for both the normal and log-normal curve were computed. The

33 percentile values for the normal curve were computed with the aid of the

Microsoft Excel statistical programme. As for the log-normal curve, since,

1(ln )z x α β −= −

Therefore, exp( )x zβ α= + …(4.32)

The upper 33 percentile was at z = 0.4317 and lower 33 percentile was at

z = -0.4317 (From Table 4.7). Using equation 4.11 and 4.13 to calculate values of

α and β , x could then be determined from equation 4.32 for both the upper and

lower 33 percentile values. These values were compared against the values from the

normal curve and tabulated in Table 4.6. It was found that the differences were

relatively small, approximately 2.5%. Therefore, this verified Grimm’s theory that

the normal distribution probability function could be used for data with c.v. less than

30 %.

98

Table 4.2: Water absorption of specimens in each sample for facing bricks

Sample

Water Absorption in specimens (%)

1 10.56 10.16 10.92 12.66 9.54 11.60 10.76 10.58 13.73 10.46 2 8.37 13.35 10.35 8.83 9.53 11.93 10.54 8.02 11.62 12.07

Batch

1 3 10.45 10.95 11.20 11.59 10.63 11.41 10.79 12.96 12.32 11.07 4 11.58 12.59 10.71 10.80 11.57 12.03 10.83 11.25 13.37 10.58 5 11.83 12.93 12.22 13.79 11.13 10.40 12.40 11.18 12.44 10.91 6 10.82 13.12 12.37 12.43 10.87 11.49 10.04 11.93 11.26 11.20 7 12.03 11.45 10.85 11.60 11.74 12.33 12.21 12.98 12.95 11.93 8 12.36 10.36 10.12 12.37 11.56 10.65 11.99 11.53 12.25 10.45 9 11.89 12.70 11.20 9.65 11.56 11.94 11.12 12.75 13.15 12.02 10 12.01 10.37 11.63 10.03 11.70 12.79 10.29 9.40 12.15 13.55

Batch 2

11 13.14 11.45 12.67 12.10 11.03 12.25 12.15 11.14 11.76 11.52 12 11.89 11.30 12.05 12.70 10.49 10.52 10.38 12.74 10.43 11.29 13 9.86 8.95 11.01 11.40 11.77 10.21 11.55 11.95 12.25 10.78 14 12.37 11.16 12.21 10.55 12.12 12.83 11.12 10.66 11.31 11.01 15 11.87 11.63 10.50 10.30 11.08 11.79 9.15 10.84 11.71 10.00 16 7.66 10.31 11.33 12.03 9.67 11.36 11.55 10.30 10.84 9.84 17 8.84 9.18 9.27 8.80 10.13 9.59 9.25 9.12 9.49 10.37 18 10.37 10.24 11.05 10.29 11.51 11.91 11.41 11.41 9.46 10.57

Batch 3

19 11.15 10.82 12.09 9.35 9.86 10.11 10.24 10.45 12.17 11.41 20 8.57 13.61 11.63 12.40 11.04 11.47 8.47 11.64 9.97 11.69 21 12.61 8.64 12.14 11.74 9.67 12.09 12.03 8.61 11.78 8.25 22 10.32 9.64 11.44 11.08 10.62 13.99 13.33 11.10 9.86 10.03 23 9.31 13.14 11.98 10.36 12.74 12.94 9.31 12.74 13.52 11.34 24 12.29 10.95 13.03 12.61 13.48 12.44 12.75 14.38 12.11 11.91 25 12.71 8.94 9.56 11.69 12.36 13.39 10.69 11.76 12.67 11.13 26 11.70 7.93 9.34 10.06 11.65 12.09 8.58 9.23 11.05 13.02

Batch 4

27 12.54 12.17 12.00 7.92 12.67 12.40 11.33 8.83 11.46 11.76 Descriptive Statistics Mean, x = 11.23% Median = 11.35 % Mode = 12.25 % Variance = 1.649 Standard deviation, s = 1.284 % Maximum = 14.377 Minimum = 7.655 Range, R = 6.72 % Coefficient of variation, c.v. = 11.43 %

99

Table 4.3: Frequency distribution of data for facing bricks

Class interval Frequency 7.555-8.255 6 8.255-8.955 15 8.955-9.655 19

9.655-10.355 24 10.355-11.055 48 11.055-11.755 59 11.755-12.455 58 12.455-13.155 28 13.155-13.855 10 13.855-14.555 3

010203040506070

7.55

5-8.

255

8.25

5-8.

955

8.95

5-9.

655

9.65

5-10

.355

10.3

55-1

1.05

5

11.0

55-1

1.75

5

11.7

55-1

2.45

5

12.4

55-1

3.15

5

13.1

55-1

3.85

5

13.8

55-1

4.55

5

Water absorption in percentage

Freq

uenc

y

Figure 4.6: Histogram, normal curve and log-normal curve, for water


Normal curve

Log- normal curve

11.23%11.3%

12.25%1.28

. . 11.4%

==

===

xMedianModesc v

Low<10.68 % Normal=10.68- 11.85 % High >11.85 %

100

Table 4.4: Normal and log-normal curve fit for water absorption

Normal curve Log-normal curve

Interval midpoint

Observed frequency

Number of standard deviations, z (x - x) s

( )f z

( ) ( )-1 2 22π exp - z 2

Computed frequency ordinate, y

( )ni f z s (Normal curve in Fig. 4.6 shown in red.)

Number of standard deviations, z ( ) -1ln x - α β

( )f z

( )( )

-0.5 -1

2

2π β

exp - z 2 - βz - α


ni f(z) (Log-normal curve in Fig. 4.6 shown as broken line.)

(1) (2) (3) (4) (5) (6) (7) (8)

7.905 6 -2.589 0.014 2.059 -3.023 0.005 0.866 8.605 15 -2.043 0.049 7.278 -2.279 0.030 5.728 9.305 19 -1.498 0.130 19.112 -1.593 0.106 19.995 10.005 24 -0.953 0.253 37.282 -0.956 0.221 41.849 10.705 48 -0.408 0.367 54.029 -0.363 0.306 57.851 11.405 59 0.137 0.395 58.167 0.193 0.301 56.933 12.105 58 0.682 0.316 46.520 0.715 0.224 42.312 12.805 28 1.228 0.188 27.639 1.208 0.132 24.889 13.505 10 1.773 0.083 12.199 1.675 0.064 12.035 14.205 3 2.318 0.027 4.000 2.119 0.026 4.934

101

Table 4.5: Normal and log-normal curve fit for compressive strengths of common bricks

Normal curve Log-normal curve

Interval midpoint

Observed frequency

Number of standard deviations, z (x - x) s

( )f z =

( ) ( )-0.5 22π exp - z 2


( )ni f z s

Number of standard

deviations, z ( ) -1ln x - α β

( )f z =

( )( )

-0.5 -1

2

2π β

exp - z 2 - βz - α


( )y ni f z=

(1) (2) (3) (4) (5) (6) (7) (8)

20.35 14 -1.695 0.095 5.025 -2.126 0.0082 3.9287 24.35 11 -1.253 0.182 9.630 -1.408 0.0243 11.6834 28.35 11 -0.812 0.287 15.191 -0.799 0.0409 19.6463 32.35 14 -0.371 0.372 19.721 -0.271 0.0476 22.8401 36.35 18 0.070 0.398 21.071 0.196 0.0431 20.6849 40.35 24 0.512 0.349 18.530 0.614 0.0328 15.73416 44.35 10 0.953 0.253 13.412 0.992 0.0220 10.5646 48.35 13 1.394 0.151 7.990 1.338 0.0135 6.4784 52.35 4 1.836 0.074 3.918 1.656 0.0077 3.7163 56.35 1 2.277 0.029 1.581 1.951 0.00423 2.0291

102

0

5

10

15

20

25

30

18.3

5-22

.35

22.3

5-26

.35

26.3

5-30

.35

30.3

5-34

.35

34.3

5-38

.35

38.3

5-42

.35

42.3

5-46

.35

46.3

5-50

.35

50.3

5-54

.35

54.3

5-58

.35


Freq

uenc

y

Figure 4.7: Histogram, normal curve and log-normal curve for compressive

strength of common bricks (c.v. approaching 30%)

Table 4.6: Comparisons of 33 percentile values from normal and log-normal

curve for compressive strength of common brick Percentile Normal curve Log-normal curve

33 31.86735 31.07525

67 39.53042 38.55586

Table 4.7: Probability that x will not be exceeded (adapted

From Grimm, 1988) Probability, % z 1 -2.3267 5 -1.645 10 -1.28 20 -0.842 25 -0.674 30 -0.524 33.3 -0.4317 40 -0.253 Mode β− 50 (median) 0 Mean 2β 60 0.253 66.7 0.4317 70 0.524 80 0.842 90 1.28 95 1.645 99 2.3267 99.5 2.575 99.9 3.10

Log-normal curve

Normal curve

103

4.3.2 Test for Data Homogeneity

The control chart was used for testing data homogeneity. The first step in the

construction of the control chart was to divide the observations into a convenient

subgroup on a time basis. The 27 samples constitute the subgroups. The means and

ranges of each sample were then determined (Table 4.8).

The means and ranges for every sample were plotted for the respective mean

and range chart (Figure 4.8 and 4.9).The upper and lower warning limits (MWL)

and action limits (MAL) for the mean chart were determined using equations 4.25

and 4.27, respectively. With respect to the range chart, the upper and lower warning

limit (RWL), were computed from equations 4.28 and 4.29 respectively. While, the

upper and lower action limits (RAL) were determined from equation 4.30 and 4.31,

respectively. These values for control limits were shown in Table 4.9.

From the control chart for sample means in Figure 4.8 it could be seen that

there were 2 points each located outside the upper and the lower action lines. These

two points from sample 17 and 24 were considered as outliers and were assumed to

contribute to the non-homogeneity of data. Therefore, to be reasonably confident

that estimates derived from samples were representative of the population these two

data points were disregarded in the analysis of the population mean. On the other

hand, the range chart in Figure 4.9 was found to be in compliance with the

requirements of homogeneity criteria of a control chart since all the data points are

within the inner control limits (RWL). This may indicate that the production had

achieved a reasonably good control over the variance.

104

Table 4.8: Sample means and ranges for water absorption

Sample no. Mean Range

1 11.098 4.186

2 10.461 5.322

3 11.337 2.512

4 11.531 2.796

5 11.923 3.396

6 11.552 3.074

7 12.007 2.131

8 11.367 2.246

9 11.797 3.496

10 11.393 4.145

11 11.921 2.117

12 11.379 2.362

13 10.973 3.297

14 11.534 2.279

15 10.887 2.718

16 10.489 4.374

17 9.404 1.572

18 10.822 2.452

19 10.765 2.816

20 11.048 5.137

21 10.756 4.358

22 11.141 4.355

23 11.738 4.210

24 12.592 3.430

25 11.489 4.454

26 10.464 5.088

27 11.309 4.751

Grand Mean, x 11.229

Mean Range, R 3.788

Table 4.9: Control limits for means and ranges for water absorption

Grand mean, x = 11.229 Mean range, R = 3.788

For means For ranges Warning lines Action lines Lower

action line Lower warning line

Upper warning line

Upper action line

0.202x R± =11.994, 10.464

0.317x R± =12.430, 10.028

0.35R× = 1.326

0.54R× =2.046

1.55R× =5.872

1.94R× =7.349

105

9,009,50

10,0010,5011,0011,5012,0012,5013,00

0 5 10 15 20 25 30

Sample NumbersW

ater

Abs

rptio

n (%

)M

ean

Figure 4.8: Control chart for mean values of water absorption

0.001.002.003.004.005.006.007.008.00

0 5 10 15 20 25 30

Sample Numbers

Wat

er A

bsor

ptio

n (%

)R

ange

Figure 4.9: Control chart for ranges of water absorption

4.3.3 Determination of Sample Variance Using the ANOVA

A single factor ANOVA at 95 % confidence was carried out on the

remaining 25 samples (Table 4.10), after ignoring the two samples i.e. sample no

17 and 24, which were found to contribute to the non-homogeneity of data. Table

4.11 shows the results from ANOVA a single factor analysis carried out using a

statistical programme by Microsoft Excel 2000. From ANOVA it was found

that calcF was smaller than critF which indicates that the differences between the

means in the samples from the different batches were not significant and therefore

Upper action line Upper warning line

Mean

Lower warning line Lower action line

Lower action line Lower warning line

Upper warning line Upper action line

Mean

106

the N.H. is accepted. From here the best estimate for the variance derived was 1.53

as shown in column 4 of Table 4.11

Table 4.10: Samples accounted for in the estimate of population

mean for water absorption

Sample

Water Absorption in specimens (%)

1 10.56 10.16 10.92 12.66 9.54 11.60 10.76 10.58 13.73 10.46 2 8.37 13.35 10.35 8.83 9.53 11.93 10.54 8.02 11.62 12.07

Batch

1 3 10.45 10.95 11.20 11.59 10.63 11.41 10.79 12.96 12.32 11.07 4 11.58 12.59 10.71 10.80 11.57 12.03 10.83 11.25 13.37 10.58 5 11.83 12.93 12.22 13.79 11.13 10.40 12.40 11.18 12.44 10.91 6 10.82 13.12 12.37 12.43 10.87 11.49 10.04 11.93 11.26 11.20 7 12.03 11.45 10.85 11.60 11.74 12.33 12.21 12.98 12.95 11.93 8 12.36 10.36 10.12 12.37 11.56 10.65 11.99 11.53 12.25 10.45 9 11.89 12.70 11.20 9.65 11.56 11.94 11.12 12.75 13.15 12.02 10 12.01 10.37 11.63 10.03 11.70 12.79 10.29 9.40 12.15 13.55

Batch 2

11 13.14 11.45 12.67 12.10 11.03 12.25 12.15 11.14 11.76 11.52 12 11.89 11.30 12.05 12.70 10.49 10.52 10.38 12.74 10.43 11.29 13 9.86 8.95 11.01 11.40 11.77 10.21 11.55 11.95 12.25 10.78 14 12.37 11.16 12.21 10.55 12.12 12.83 11.12 10.66 11.31 11.01 15 11.87 11.63 10.50 10.30 11.08 11.79 9.15 10.84 11.71 10.00 16 7.66 10.31 11.33 12.03 9.67 11.36 11.55 10.30 10.84 9.84 18 10.37 10.24 11.05 10.29 11.51 11.91 11.41 11.41 9.46 10.57

Batch 3

19 11.15 10.82 12.09 9.35 9.86 10.11 10.24 10.45 12.17 11.41 20 8.57 13.61 11.63 12.40 11.04 11.47 8.47 11.64 9.97 11.69 21 12.61 8.64 12.14 11.74 9.67 12.09 12.03 8.61 11.78 8.25 22 10.32 9.64 11.44 11.08 10.62 13.99 13.33 11.10 9.86 10.03 23 9.31 13.14 11.98 10.36 12.74 12.94 9.31 12.74 13.52 11.34 25 12.71 8.94 9.56 11.69 12.36 13.39 10.69 11.76 12.67 11.13 26 11.70 7.93 9.34 10.06 11.65 12.09 8.58 9.23 11.05 13.02

Batch 4

27 12.54 12.17 12.00 7.92 12.67 12.40 11.33 8.83 11.46 11.76 Mean = 11.247

Table 4.11: ANOVA and components of variance for water absorption Source of Variation

Sum of square

(SS)

Degrees of

freedom (df)

Mean square (MS)


When the N.H. is rejected the mean square is an estimate of

calc.F

between

within

MSMS

÷

crit.F From

F-Table

(1) (2) (3) (4) (5) (6) (7) (8)

Between rows 51.487 24 2.1453 2σ 2 2rcσ σ+

Within rows 329.94 225 1.4664 2σ 2σ

Total 381.43 249 1.53 Best estimate of

2σ

1.463 1.566

107

4.3.4 Estimates of Population Mean

The estimates for the population meanµ , were determined using equation

4.18. This estimate was based on the remaining 25 samples (Table 4.10) after

ignoring data from sample 17 and 24, which were considered as not representative

of the population.

csx tn

µ = ±

Where,

x = mean for sample = 11.247 (Table 4.10)

tc = 2.262 (From Appendix B, Table B2)

s =sample standard deviation = 1.53 ( 2 1.53s = derived from ANOVA)

n = sample size = 10

1.5311.247 2.262 10.36 12.1310

toµ∴ = ± =

The mean for water absorption in percentage was11.247 0.885± i.e. ranging

from 10.36 % to 12.13 %. Therefore, water absorption for the population falls in the

range of 10 % - 12 %.

4.4 Conclusions

In norm with the central limit theorem it is widely acknowledged that most

physical measurements could be assumed normally distributed. On this basis

therefore, the normal probability function has been used throughout this work for

processing sample data. The validity of the normally distributed assumption is

verified as shown by the results of the histogram plot for the various tests. A typical

example taken for the water absorption tests showed that most data were

concentrated about the mean and it could be assumed that the histogram would

approach a normal curve as the size of data increases. Similarly, the other results

108

comprising of the dimensional tolerance, IRS, density and compressive strength also

displayed comparable characteristics of a normally distributed data.

The population mean derived from normal probability curve is good if size

of sample is large i.e. a sample having more than 30 data. In this work, however,

there were less than 30 bricks in a sample. Hence, the sample was considered small.

Under this condition the percentage points from the t-distribution curve was used to

derive the population estimates.

Control charts are graphical techniques used mainly to assess quality of a

production. It consists of performance data plotted against the control limits, i.e. the

upper and lower action and warning lines. These control limits define the constraints

for variations and if exceeded shows that the process is out of control or data is not

homogeneous. For this research samples, which did not satisfy the homogeneity

criteria, set by these control limits were considered as not representative of the

population and were not accounted for in the derivation of population estimates.

In a normal curve, data are symmetrically distributed about the mean, i.e. the

mean, median and mode are all coincident on the curve. The histogram plotted for

data in this work reveals some skewness in the data distribution for which the mean,

median and mode were not coincident. For this case, the coefficient of variation

(c.v.) is used to indicate the reliability of the assumption of a normal curve. Grimm

suggested that the log-normal probability function would be found helpful for data

having c.v.’s exceeding 30 %. In the log-normal distribution the natural logarithm is

normally distributed. With respect to this, the c.v.’s determined for dimensional

tolerance, density, IRS, water absorption and compressive strengths, for facing

bricks loaded on its bed and stretcher face and common bricks were all below 30 %

and therefore did not need the log-normal probability function. However, to further

justify the appropriateness of the normal probability function application in the

analyses, the 33-percentile values for the compressive strength of common bricks

with a c.v. of 25.4 % were computed for both the normal and log-normal curves.

Results showed comparatively small differences between the two values verifying

that the normal probability function could be used for data with c.v. less than 30 %.

109

In this research samples were taken from the factory in different batches at

intervals of approximately two months. Therefore to ascertain that the differences of

the means in the different batches were not significant a single factor ANOVA was

computed. From the ANOVA the components of variance between the several

samples in the different batches were determined. The variance was then used in

arriving at the population mean.

CHAPTER 5

RESULTS AND DISCUSSIONS

5.1 Introduction

This chapter presents results for the compressive strength, dimensional

tolerance, water absorption, initial rate of suction, density, efflorescence effects and

soluble salt content of bricks. The results were analysed and interpreted through the

process as described in Chapter IV. Comparisons and correlations of the results with

specified limits of other standards were also carried out for the purpose of

evaluation.

Results from efflorescence test and soluble salt content were deduced from

observations based on small samples and hence found not required to be analysed by

the statistical approach as described in Chapter IV.


The compressive strength of facing brick was determined with respect to the

different orientations of testing i.e. on its bed face, stretcher face and header face.

The common bricks were only tested on their bed face. The loaded area used in the

calculation of compressive strength in all cases was the gross area. However,

111

compressive strength for results tests conducted on the bed face was also compared

with results based on calculations using net loaded area. The net loaded area is the

gross area less the area of perforations.

Table 5.1, 5.2 and 5.3 show the compressive strengths of specimens in the

samples for all batches of facing bricks when tested on their bed, stretcher and

header face respectively.

Table 5.1: Compressive strength of specimens in each sample for facing

bricks tested on bed face Sample Compressive strength N/mm2

1 42.0 46.5 43.7 47.6 38.1 38.0 35.3 42.2 33.1 39.6

Batch 1 2 48.8 43.2 44.6 43.8 50.3 51.3 51.7 55.0 44.5 54.0

3 35.6 41.8 44.7 35.8 31.0 45.5 40.6 35.5 42.9 36.2 4 36.5 41.1 48.4 38.5 30.6 29.4 27.1 38.3 35.6 29.7 5 56.3 41.0 57.7 41.8 34.1 46.5 52.0 59.0 40.0 42.1

Batch 2

6 39.9 39.0 45.8 48.6 40.4 43.3 38.7 48.8 54.6 57.6 7 61.8 59.1 54.8 72.5 60.0 59.5 63.6 66.1 46.8 44.4 8 45.5 51.1 50.3 49.9 28.8 55.4 56.6 53.1 68.4 53.2 9 53.5 42.1 53.8 48.5 47.7 50.4 50.7 54.5 60.7 47.7

Batch 3

10 48.2 52.2 52.4 40.6 55.5 53.5 50.2 47.0 49.9 48.7 11 45.4 43.2 42.6 53.5 38.4 40.4 41.2 48.8 44.3 43.6 12 51.8 35.2 47.8 40.0 41.9 45.3 42.4 59.0 34.0 36.1 13 64.1 48.9 40.9 57.8 51.2 38.5 39.2 42.7 39.5 36.8

Batch 4

14 39.4 41.5 50.1 41.6 39.8 41.2 56.6 48.6 43.5 40.6 Descriptive Statistics Mean, x = 46.07 N/mm2 Median = 45.01 N/mm2 Mode = NA Standard deviation, s = 8.55 N/mm2 Maximum = 72.5 N/mm2 Minimum = 27.1 N/mm2 Range, R = 45.4 N/mm2 Coefficient of variation, c.v. = 18.5 %

112

Table 5.2: Compressive strength of specimens in each sample for facing

bricks tested on stretcher face Sample Compressive strength of specimens N/mm2

1 39.3 39.4 34.8 38.9 39.4 37.1 36.9 36.8 37.0 33.4

Batch 1 2 33.8 26.8 33.5 32.6 28.9 38.0 31.4 27.9 30.9 27.0

3 35.3 37.7 43.5 34.0 34.4 29.7 22.5 34.4 35.0 35.4 Batch 2 4 34.4 35.7 33.2 40.2 34.5 35.3 37.7 43.5 34.0 27.5

5 40.9 49.5 44.6 45.3 38.9 44.8 44.0 35.6 55.0 43.0 Batch 3 6 37.9 28.3 33.7 38.0 34.0 47.8 37.5 37.9 35.1 36.9

7 22.2 31.3 45.5 37.8 25.9 30.0 32.7 30.1 27.8 24.0 Batch 4 8 28.9 23.8 26.5 25.6 25.3 27.9 29.7 30.9 30.9 34.4

Descriptive Statistics Mean, x = 34.74 N/mm2 Median = 34.49 N/mm2 Mode = 35.27 N/mm2 Standard deviation, s = 6.45 N/mm2 Maximum = 55.0 N/mm2 Minimum =22.2 N/mm2 Range, R = 32.8 N/mm2 Coefficient of variation, c.v. = 18.6%

Table 5.3: Compressive strength of specimens in each sample for

facing bricks tested on header face. Sample Compressive strength N/mm2

1 9.5 9.3 9.0 9.2 8.0 8.4 7.9 9.2 8.8 9.1

Batch 1 2 2.7 4.0 3.5 3.9 2.3 4.5 3.6 3.1 4.3 4.2

3 5.0 4.3 4.6 2.2 4.6 6.9 4.7 4.7 5.4 2.5 Batch 2 4 5.4 5.4 5.1 6.2 4.1 5.0 4.3 4.6 5.1 4.6

5 10.6 5.6 4.3 7.2 5.5 11.4 7.6 6.7 6.1 7.6 Batch 3 6 4.5 5.6 3.9 4.7 4.2 5.0 4.7 3.2 3.0 6.9

7 5.5 2.4 3.2 3.7 5.6 3.2 4.3 5.6 0.8 3.0 Batch 4 8 8.4 8.9 5.5 6.0 7.3 6.4 6.1 6.9 4.8 5.8

Descriptive Statistics Mean, x = 5.51 N/mm2 Median = 5.07 N/mm2 Mode = 5.03 N/mm2 Standard deviation, s = 2.15 N/mm2 Maximum = 11.4 N/mm2 Minimum = 0.8 N/mm2 Range R =10.06 N/mm2 Coefficient of variation, c.v. =39.0 %

The descriptive statistics consisting of the mean, median, mode, standard

deviation, range and coefficient of variation were shown in Table 5.1, 5.2 and 5.3.

The mean compressive strength was 46.1, 34.7 and 5.51 N/mm2 when tested on bed,

stretcher and header face respectively. With a mean strength of 46 N/mm2 when

tested on the bed face, the bricks from this research easily surpass the top range of

113

the specified limits for ASTM, AS and the SS with exception of the Engineering

category of the BS (Table 5.8).

Data distribution was presented by the histograms as shown in Figure 5.1.

The histogram could be seen to represent a normally distributed data and in virtue of

the central limit theorem the histogram would eventually form a normal curve with

increasing number of data. Hence, assuming data to be normally distributed the

normal curve fit (Table 5.4) was computed for the compressive strengths tested on

the bed and stretcher face (having c.v.’s of 18.5 % and 18.6 % respectively). With

respect to the bricks tested on the header face the c.v. was 39.0 % which was greater

than 30 %. Therefore, the compressive strengths tested on the header face were fitted

with a log-normal curve (Table 5.5). The normal and log-normal curves were plotted

superimposed on the histograms as shown in Figure 5.1.

Table 5.4: Normal curve fit for compressive strength of facing bricks tested

on bed and stretcher face Testing

orientations Interval midpoint

x

Observed frequency

Number of standard

deviations, z (x - x) s

( )f z =

( ) ( )π -1 2 22 exp - z 2


( )nif z s 29.269 6 -1.966 0.0577 4.2918 33.807 9 -1.435 0.1424 10.587 38.345 24 -0.904 0.265 19.701 42.883 31 -0.373 0.3721 27.655 47.421 23 0.1576 0.394 29.285 51.959 23 0.6886 0.3147 23.392 56.497 12 1.2195 0.1896 14.096 61.035 7 1.7505 0.0862 6.4072 65.573 3 2.2814 0.0296 2.197 70.111 1 2.8124 0.0076 0.5683

Bed face

74.649 1 3.3433 0.0015 0.1109 23.642 4 -1.727 0.0898 3.6622 26.925 11 -1.217 0.1902 7.7552 30.208 11 -0.707 0.3106 12.6652 33.491 18 -0.198 0.3912 15.9513 36.774 18 0.312 0.3799 15.4933 40.057 7 0.822 0.2846 11.6054 43.340 6 1.331 0.1644 6.7041 46.623 3 1.841 0.0732 2.9866 49.906 1 2.351 0.0252 1.0261 53.189 0 2.861 0.0067 0.2719

Stretcher face

56.472 1 3.370 0.0014 0.0556

114

Table 5.5: Log-normal curve fit for compressive strength of facing

brick tested on header face Interval midpoint

x

Observed frequency

Number of standard

deviations, z ( ) -1ln x - α β

( )f z =

( )( )

-0.5 -1

2

2π β

exp - z 2 - βz - α


ni f(z)

1.034 1 -4.253 0.000 0.010 2.101 4 -2.370 0.030 2.594 3.168 9 -1.280 0.147 12.587 4.235 22 -0.509 0.220 18.759 5.302 17 0.088 0.199 16.988 6.369 9 0.575 0.141 12.035 7.436 6 0.986 0.088 7.478 8.503 5 1.342 0.051 4.321 9.570 5 1.656 0.028 2.398 10.637 1 1.937 0.015 1.303 11.704 1 2.190 0.008 0.701

From the normal and log-normal probability functions the 33-percentile

values for all the three cases of loadings were determined and are shown in Figures

5.1 (a), (b) and (c). The high and low values were meant for the upper and lower 33-

percentile while the medium values were for the middle third distribution. The upper

33-percentile for bricks tested on the bed face i.e. about one-third of the distribution

had compressive strengths exceeding 50 N/mm2 i.e. the minimum requirements for

Engineering B bricks of the BS.

The mean compressive strength representative of the population of bricks in

the study was computed after examining the homogeneity of data using the control

charts for means and ranges of samples (Figure 5.2). Data not complying with the

homogeneity criteria as explained in Chapter IV were not taken into account when

determining the population mean. In this case the control charts showed that data

from samples 4 and 7 of the bed face compressive strengths, 5 and 8 of the stretcher

face and 1, 2, 5 and 7 of the header face were lying outside the upper and lower

action lines and thus data from these samples were ignored for the computation of

population mean.

115

0

5

10

15

20

25

30

35

27.0

00-3

1.53

8

31.5

38-3

6.07

6

36.0

76-4

0.61

4

40.6

14-4

5.15

2

45.1

52-4

9.69

0

49.6

90-5

4.22

8

54.2

28-5

8.76

6

58.7

66-6

3.30

4

63.3

04-6

7.84

2

67.8

42-7

2.38

0

72.3

80-7

6.91

8

Compressive Strength, N/mm2Fr

eque

ncy

(a) Bed face

0

5

10

15

20

22.0

0-25

.283

25.2

83-2

8.56

6

28.5

66-3

1.84

9

31.8

49-3

5.13

2

35.1

32-3

8.41

5

38.4

15-4

1.69

8

41.6

98-4

4.98

1

44.9

81-4

8.26

4

48.2

64-5

1.54

7

51.5

47-5

4.83

54 8

3-58

.113

Compressive strength, N/mm2

Freq

uenc

y

(b) Stretcher face

0

5

10

15

20

25

0.50

0-1.

567

1.56

7-2.

634

2.63

4-3.

701

3.70

1-4.

768

4.76

8-5.

835

5.83

5-6.

902

6.90

2-7.

969

7.96

9-9.

036

9.03

6-10

.103

10.1

03-1

1.17

11.1

7-12

.237

Compressive strength, N/mm2

Freq

uenc

y

(c) Header face

Figure 5.1: Histogram, normal and log-normal curve for compressive

strength of facing bricks tested on (a) bed face (b)

stretcher face (c) header face

2

2

2

2

5.5 /2.15 /

. . 39.0%5.1 /

mod 5.0 /

x N mms N mmc vmedian N mm

e N mm

===

==

Low < 42.0 N/mm2 Medium 42.0 – 50.0 N/mm2 High > 50.0N/mm2



Log-normal curve

Normal curve

Normal curve

2

2

2

2

34.7 /6.45 /

. . 18.56%34.5 /

mod 35.3 /


e N mm

===

==

2

2

2

46.1 /8.55 /

. . 18.55%45.0 /

mod


e NA

===

==

116

30

40

50

60

70

0 5 10 15

Sample

Com

pres

sive

stre

ngth

Mea

n

20253035404550

0 5 10

Sample

Com

pres

sive

stre

ngth

M

ean

2

4

6

8

10

0 5 10

Sample

Com

pres

sive

stre

ngth

M

ean

01020304050

0 5 10 15

Sample

Com

pres

sive

stre

ngth

Ran

ge

0

10

20

30

40

0 5 10

Sample

Com

ress

ive

stre

ngth

sR

ange

0

2

4

6

8

0 5 10

Sample

Com

pres

sive

stre

ngth

Ran

ge

(a) Bed face (b) Stretcher face (c) Header face

UAL – Upper action line UWL –Upper warning line LAL – Lower action line LWL – Lower warning line

Figure 5.2: Control charts of mean values and ranges for compressive strength tested on (a) bed face

(b) stretcher face (c) header face

UAL

xUWL

LWL LAL

UAL UWL x LWL LAL

UAL UWL

LWL LAL

x

UAL

UWL

x LWL LAL

UAL UWL

x LWL LAL

UAL UWL x

LAL LWL

117

The ANOVA for compressive strengths tested on the different orientations

were carried out on the remaining samples. From the ANOVA, shown in Table 5.7

Fcal. for all cases were found greater than Fcrit and therefore, the N.H. was rejected

indicating that there was significant difference in the variances of the various

samples. The ANOVA from Table 5.7 also gave the components of variance, which

were used to determine the population mean. Detail explanation of the procedures

for the determination of variance from ANOVA and derivation of population mean

is shown in Chapter IV. The estimate of variances for the different orientations of

loading were 54.40, 28.32 and 10.757 tested on bed, stretcher and header face

respectively.

Table 5.6: ANOVA and variance components for compressive strengths of

facing bricks tested on bed, stretcher and header faces Testing

orientations Source of Variation

Sum of Squares

(SS)

Degree of

freedom

(df)

Mean Square


When the N.H. is

rejected the mean square is an estimate

of

calc.F crit.F

(1) (2) (3) (4) (5) (6) (7) (8) Between samples 1672.023 11 152.002 2σ 2 2

rcσ σ+

Within samples 4704.06 108 43.556 2σ 2σ

Bed face


2σ

3.489 1.878

Between samples 398.699 5 79.740 2σ 2 2

rcσ σ+

Within samples 1220.659 54 22.605 2σ 2σ Stretcher

face


2σ

3.528 2.386

Between samples 29.687 3 9.896 2σ 2 2

rcσ σ+

Within samples 46.151 36 1.282 2σ 2σ Header face


2σ

7.719 2.866

The corresponding mean compressive strengths for the population tested on

bed, stretcher and header face were in the range of 40 to 51 N/mm2, 30 to 38 N/mm2

and 4.1 to 6.2 N/mm2.

118

Comparisons with other standards shows that the population mean, like the

sample mean supersedes the top range compressive strengths of ASTM, AS and SS.

However, the population did not fit in the category of Engineering A and B of the

BS which requires a minimum compressive strength of 70 N/mm2 and 50 N/mm2

respectively.

Results from the tests clearly demonstrated that a considerable amount of

compressive strength reduction occurred with increased slenderness ratio for the

bricks orientations. Samples results show that a maximum strength of 46 N/mm2

was achieved when brick was tested on its bed face. When tested on the header face

the compressive strength was less than 20 % of that on bed face. Similarly, the

compressive strength when tested on the stretcher face reduced to 34.74 N/mm2, i.e.

a reduction by about 20 % in comparison to bed face.

These results, showing the relative compressive strength reduction

corresponding to the different orientations of testing were approximately in

agreement with the study reported by Hendry (1997). Hendry showed that, bricks

tested on the stretcher and header faces produced compressive strength of about 80

% and 20 % respectively of the strength when tested on the bed face (Table 2.1).

The reduction in compressive strength was due to the effects of platen

restraint, which imposed a degree of confinement to the specimens, the greater the

height of specimen during testing the lesser was the platen effects. In the Australian

Standard the effect of platen restraint are being considered by multiplying the

compressive strength with a factor depending on the height to thickness ratio

(Table 2.2) and it diminishes at height to thickness ratio of 5 and above.

A relationship between compressive strength and height to thickness ratio

was developed in this study. The mean values ( x ) for the three orientations of

testing i.e. on bed (46.1 N/mm2), stretcher (34.7 N/mm2) and header faces (5.5

N/mm2) were plotted against the height to thickness ratio as shown by the graph in

Figure 5.3. The value of the height to thickness ratio (h/t) was based on the mean

measurements of both dimensions for samples used in the study. The graph for the

119

compressive strength versus h/t ratio was plotted and joined with a best fit line

described by equation 5.1 with a regression coefficient of R2 = 0.998

16.353 58.168f x= − + …(5.1)

Where,

f = compressive strengths in N/mm2

x = ratio of height to thickness (h/t).

Where,

h = the height in relation to the orientation of tests

t = the smallest dimension of the loaded face.

This relationship was derived specifically for standard format bricks with 5

rectangular slots. The equation can also provide estimation on the compressive

strength of bricks for the same standard format made from the same material or

comprised of the same amount of perforations. In this respect, the perforations are

rectangular with an average area of 3375 mm2 i.e. about 16 % of the total gross area.

The results could also be used to estimate the compressive strength of the same brick

format with circular holes as generally used in other manufacturing, however the

prediction is expected to be conservative in view that shearing will occur at higher

levels at failure.

f = -16.353x + 58.168R2 = 0.998

0

10

20

30

40

50

0 0.5 1 1.5 2 2.5 3 3.5Height to thickness ratio, h/t

Com

pres

sive

stre

ngth

, fN

/mm

2

Figure 5.3: Relationship between compressive strength and h/t ratio of bricks

Bed face h/t = 0.7

Stretcher face h/t =1.5

Header face h/t =3.2

120

The calculation for compressive strength specified in standards could either

be based on the net or gross area of loaded face. Australian Standard uses the net

area i.e. gross area less the area of perforations while ASTM specifies that the

compressive strength to be calculated using gross area. BS specified the area used in

the calculation as the overall dimension.

Compressive strengths of bricks tested on bed face determined using net area

i.e. the mean area of bed face less the area of the 5 rectangular slots is shown in

Table 5.7. The mean compressive strength was 54.4 N/mm2, which indicates an

increase of about 20 % compared to values obtained using the gross area. The

population mean was in the range of 50 to 60 N/mm2. Thus, taking into account the

net area resulted in a higher value, which qualifies the bricks as Engineering B of the

BS.

Table 5.7: Compressive strengths of facing brick tested on bed face as

computed from net areas Sample Compressive strength based on net area, N/mm2

1 49.9 55.2 51.8 56.3 45.0 45.1 41.7 50.0 39.4 47.0

Batch 1 2 57.7 51.0 52.9 51.6 59.5 60.9 61.4 65.1 52.7 64.1

3 41.8 49.9 53.3 42.1 36.6 54.3 48.0 41.8 50.7 42.9 4 43.4 48.5 57.6 45.4 36.1 35.0 32.1 45.1 42.1 35.2 5 66.9 48.2 68.1 49.2 40.2 55.2 61.6 69.9 47.2 49.6

Batch 2

6 46.9 45.9 54.0 57.5 47.6 51.1 45.5 57.8 65.2 68.3 7 73.3 70.0 64.8 86.5 71.2 70.5 75.7 78.6 55.5 52.5 8 53.8 60.5 59.6 59.1 34.2 65.8 67.2 63.1 81.5 63.1 9 63.7 49.9 63.6 57.2 56.7 59.7 60.2 64.7 72.1 56.3

Batch 3

10 57.2 62.1 62.1 48.1 65.9 63.5 59.4 55.8 59.2 57.7 11 53.8 51.2 50.5 63.6 45.4 48.1 48.8 58.1 52.8 51.6 12 61.4 41.3 57.0 47.3 49.6 53.8 50.2 70.0 40.0 42.4 13 76.1 58.0 48.4 68.9 60.6 45.5 46.1 50.6 46.7 43.7

Batch 4

14 20.0 49.5 60.3 49.2 47.1 48.8 67.6 58.0 51.6 48.0 Descriptive Statistics Mean, x = 54.4 N/mm2 Median = 53.5 N/mm2 Mode = NA Standard deviation, s = 10.62 N/mm2 Maximum = 86.5 N/mm2 Minimum = 20.0 N/mm2 Range, R = 66.5 N/mm2 Coefficient of variation, c.v. = 19.5 %

121

A relationship between compressive strength with h/t ratio considering net

loaded area for the bed face orientation is shown in Figure 5.4. The relationship

shows an increase of about 13 % in the compressive strength compared to the results

obtained by considering gross area of the bed face. Thus, the relationship of

compressive strength to h/t ratios given by equation 5.1 for perforated bricks is

considered as conservative.

f = -19.187x + 66.07R2 = 0.9913

0102030405060

0 0.5 1 1.5 2 2.5 3 3.5

Height to thickness ratio, h/t

Com

pres

sive

stre

ngth

, fN

/mm

2

Figure 5.4: Relationship between the computed compressive strength

(based on net loaded area of bed face) to h/t ratio

It should be noted that in this study compressive strength tests were carried

out after the test for water absorption. In this case, the bricks were in a saturated

condition and research has shown that wet bricks tend to show lower strengths than

dry ones. Grimm, (1975), reported that dry brick can be 15% stronger than wet ones.

Some compressive tests done on dry bricks in this study also showed that the dry

bricks had strengths of about 15 to 20 % higher than the wet bricks.

The tests conducted on wet bricks based on gross area yield lower

compressive strengths as the effects of curing and gross loaded area contribute to

both physical and theoretical determination of strength. Consequently, the evaluation

of compressive strength of bricks studied in this research implies conservative

results compared to values stated in ASTM.

Bed face h/t = 0.7

Stretcher face h/t = 1.5

Header face h/t = 3.2

122

Table 5.8: Compressive strength of facing and common bricks and standard requirements

Compressive strength from research results BS (Mean of 10

bricks) ASTM (Mean of

5 bricks) AS

(Characteristic strength)

SS (Mean of 10 bricks)

Mean Engineering Ratio of manufacturing height to width

Testing orientations Population

µ

Sample x

High (Upper 33-percentile)

Normal (Middle 33-percentile)

Low (Lower 33-percentile) A B Others

SW

MW

NW

≤ 0.7 ≥ 2

Firs

t gra

de

Seco

nd g

rade

Thi

rd g

rade

Bed face . 67 0.7

98ht= ≈

40.0 – 51.0 46.00 >50.0 42.0 – 50.0 <42.0 ≥ 70

≥ 50 ≥ 5

Not less than 20.7

Not less than 17.2

Not less than 10.3

Not less than 7.0

Not less than 5.0

Not less than 35.0

Not less than 20.0

Not less than 5.2

Stretcher face 98 1.567

ht= ≈

30.0 – 38.0 34.7 >37.0 33.0 – 37.0 <33.0

Facing brick

Header face 216 3.267

ht= ≈

4.12 – 6.20 5.5 >6.0 4.0– 6.0 <4.0

Common bricks

Bed face 30.0 – 40.0 35.7 >40.0 32.0 – 40.0 <32.0

123

Results for compressive strength of common bricks are shown in Table 5.9.

In this study common bricks were referred to bricks for general building works with

no aesthetic application

Table 5.9: Compressive strength of specimens in each sample for common

bricks Sample Compressive strength determined from net area, N/mm2

1 38.5 39.5 29.0 40.0 31.1 36.1 25.2 39.4 27.8 34.0 2 39.6 38.0 36.1 27.2 39.5 33.5 25.1 36.3 34.2 32.3

Batch

1 3 38.8 37.7 29.3 38.9 26.5 36.5 25.1 37.8 27.8 34.0 4 28.5 25.9 22.5 25.2 22.7 24.7 21.3 24.4 20.1 22.2 5 21.0 27.2 39.1 39.0 33.7 32.9 35.4 31.7 39.2 40.2 Batch

2 6 20.6 26.2 19.0 25.3 23.1 24.6 20.7 36.2 18.4 21.7 7 29.6 37.9 26.8 30.8 28.6 33.6 31.7 21.2 20.2 46.0 8 41.6 42.8 36.4 38.4 41.4 48.6 49.8 39.6 43.6 40.9 Batch

3 9 34.1 38.4 36.7 35.7 40.5 47.3 49.0 36.9 45.5 40.9 10 51.4 58.0 51.7 49.2 50.4 49.1 47.0 46.7 47.2 34.2 11 38.4 44.1 44.4 38.1 49.1 45.2 48.9 39.6 48.2 33.1 Batch

4 12 48.6 34.6 44.5 25.8 41.9 50.1 45.0 43.7 41.6 34.2 Descriptive Statistics Mean, x = 35.71 N/mm2 Median = 36.42 N/mm2 Mode = 40.86 N/mm2 Standard deviation, s = 9.06 N/mm2 Maximum = 58.0 N/mm2 Minimum = 18.4 N/mm2 Range, R = 39.6 N/mm2 Coefficient of variation, c.v. = 25.4 %

0

5

10

15

20

25

30

18.3

5-22

.35

22.3

5-26

.35

26.3

5-30

.35

30.3

5-34

.35

34.3

5-38

.35

38.3

5-42

.35

42.3

5-46

.35

46.3

5-50

.35

50.3

5-54

.35

54.3

5-58

.35

Compressive strength N/mm2

Freq

uenc

y

Normal curve

Figure 5. 5: Histogram and normal curve for compressive strength of

common bricks

2

2

2

2

35.7 /9.06 /

. . 25.38%36.4 /

mod 40.9 /


e N mm

===

==

Low < 31.87 N/mm2 Medium 31.87 – 39.50 N/mm2 High > 39.50 N/mm2

124

The histogram and the normal curve fit is shown in Figure 5.5. The sample

mean was 36 N/mm2, which lie within the ranges specified for structural bricks of

ASTM for the category of SW bricks and just exceed the minimal requirement

specified of First Grade brick in Singapore Standard. However, from the normal

curve function the middle 33-percentile comprises of strengths in the range of 31.9

to 39.5 N/mm2 exceeding values for the top range of the structural bricks of ASTM

(Table 5.7).

The quality control charts (Figure 5.6) shows that 5 out of 12 samples lie

outside the upper and lower action lines thus indicating considerable scatter of

compressive strengths. This is in contrast with the results observed for facing bricks.

The wide scatter of data for common bricks shows lacking of production control.

However, it must be borne in mind that some of the common bricks were rejected

products of facing brick, therefore the properties might not be consistent with actual

common bricks production.

The population mean was derived after ignoring these 5 data points. The

variance from the ANOVA was 48.55 from which the standard deviation of the

population is estimated as 6.968 N/mm2. The population mean range computed

using this standard deviation was 30.38 to 40.34 N/mm2 and this value exceeds the

requirements for SW bricks of ASTM. and Second grade bricks of the Singapore

Standard.

The compressive strength ranged from 30 to 40 N/mm2, therefore the

common bricks in this study suffice the requirements for structural bricks under the

classification of SW bricks of the ASTM. The common bricks investigated in this

study could be used as load-bearing applications although not suitable for facing

brickwork due to lacking of other physical and dimensional properties. Previous

research on common bricks of the same manufacturer’s product showed water

absorption exceeding 10%.

125

20,0

30,0

40,0

50,0

0 2 4 6 8 10 12 14

Sample

Com

pres

sive

stre

ngth

M

ean

0,0

10,0

20,0

30,0

40,0

0 2 4 6 8 10 12 14

Sample

Com

pres

sive

stre

ngth

Ran

ge

UAL

UWL

xLWLLAL

Figure 5.6: Control charts of mean values and ranges of samples for

compressive strength of common bricks

5.3 Dimensional Tolerance

5.3.1 Overall Dimensions of 24 Bricks

Table 5.10 shows the results of overall dimension of length, width and height

of 24 bricks and the deviations of these dimensions from the work sizes for the

individual brick. These deviations were derived from the results of the overall

dimensions as shown in Table 5.10 columns (4), (6) and (8). The work sizes were as

given in the BS for length, width and height i.e. 215 mm, 102.5 mm and 65 mm

respectively. The mean value of overall length was 5218 mm, which is within the

limits of BS i.e. 5085 mm to 5235 mm. The mean value of overall width of

2412 mm was slightly out of range compared to the BS limits of 2415 mm to 2505

mm. The height had a mean value of 1642 mm, exceeding the limit of BS by 37 mm.

UAL UWL xLWL LAL

126

Table 5.10: Overall measurement of length, width and height of 24 bricks

and individual brick dimensional deviations from work size

Sam

ple

Overall Length of 24

bricks

Deviations of Individual

length of brick from work

size [(3)÷ 24]- 215

Overall width of

24 bricks

Deviations of individual width

of brick from work size

[(5)÷ 24]- 102.5

Overall height of 24

bricks

Deviations of individual

height of brick from work size

[(7)÷ 24]- 65 (2) (3) (4) (5) (6) (7) (8) 1 5240 3.33 2415 -1.88 1638 3.25

(1)

Batch 1

2 5254 3.92 2410 -2.08 1646 3.58 3 5216 2.33 2408 -2.17 1648 3.67 4 5263 4.29 2426 -1.42 1651 3.79 5 5241 3.38 2421 -1.63 1650 3.75

Batch

2 6 5243 3.46 2419 -1.71 1653 3.88 7 5175 0.63 2405 -2.29 1628 2.83 8 5218 2.42 2412 -2.00 1640 3.33 9 5185 1.04 2413 -1.96 1625 2.71

Batch

3 10 5178 0.75 2397 -2.63 1634 3.08 11 5203 1.79 2416 -1.83 1638 3.25 12 5211 2.13 2400 -2.50 1643 3.46 13 5210 2.08 2409 -2.13 1643 3.46

Batch

4 14 5213 2.21 2414 -1.92 1644 3.50

Descriptive statistics Mean, x 5218 2.41 2412 -2.01 1642 3.40 Median 5215 2413 1643 Mode #N/A #N/A 1638 Standard deviation, s 27.55

7.86

8.35

Maximum 5263 2426 1653 Minimum 5175 2397 1625 Range, R 88 29 28 c.v. 0.53% 0.33% 0.51%

Max. Min. Max. Min. Max. Min. British Standard 5235 5085 2505 2415 1605 1515 Note: Work sizes as in BS 3921:1985 – Length = 215 mm, width = 102.5 mm, height = 65 mm

A plot of sample overall dimensions against specified limits of BS and SS is

shown in Figure 5.7. The SS provides three grades of dimensional tolerance i.e. first,

second and third grade, depending on the degree of dimensional accuracy required,

however bricks under the category of the third grade are not limited to any

dimensional tolerance.

Figure 5.7 clearly demonstrates that the bricks in this research had lengths

and widths marginally in agreement with the BS and SS first grade bricks but the

height was oversize. The length belongs to the higher range of the BS as evident by

127

5 samples lying outside the upper range [Figure 5.7 (a)], while the width were in the

lower range of the BS with 5 samples lying below the lower range of the width

measurement [Figure 5.7 (b)]. On the other hand, all samples for the height exceeds

the maximum limit of the British Standard.

5000

5100

5200

5300

5400

5500

0 5 10 15 20

Sample

Ove

rall

Len

gth

(mm

)

(a)

2350

2400

2450

2500

2550

2600

0 5 10 15 20

Sample

Ove

rall

Wid

th (m

m)

BS and SS First Grade

SS Second Grade

(b)

1460

1510

1560

1610

1660

1710

1760

1810

0 5 10 15 20Sample

Ove

rall

Hei

ght (

mm

)

BS SS First Grade

SS Second Grade

(c)

Figure 5.7: Comparison of overall dimensions of (a) length (b) width and

(c) height with allowable range of British and Singapore Standard.

SS Second Grade

BS and SS First Grade

128

The dimensional tolerance of the bricks investigated in this research was also

evaluated against values of tolerances provided in the European Standard

prEN 771-1 and the derived tolerance limit for individual brick based on the

cumulative measurement of 24 bricks. Table 5.11 shows the comparisons of

dimensional tolerances for individual brick from results of this research (col. 2) with

values derived from specified tolerance for 24 bricks of BS 3921 (col.5) and the

tolerance categories of T1 and T2 in prEN 771-1 (col. 3 and 4). In the prEN 771-1

the mean dimensions of 10 bricks in a sample should not differ from the declared

value of either categories T1 and T2, which correspond to the following:

T1: 0.4 (work size dimension)± mm or 3 mm whichever is greater.

T2: 0.25 (work size dimension)± mm or 2 mm whichever is greater.

The dimensional deviations for individual brick derived from BS 3921

(col.5), was calculated based on the limits given for the overall dimensions of 24

bricks. For example, the overall length of 24 bricks should not exceed 5235 mm and

not less than 5085 mm, which equal to a tolerance of 6.25 mm or 3± .125 mm for

the length of individual brick.

Table 5.11: Dimensional deviations of brick from work size and comparisons

with values of dimensional tolerance for BS 3921:1985 and prEN

771-1

prEN 771-1 Dimensional tolerance for BS work

size.

Dim

ensi

ons

Test results of mean dimensional deviations from work size derived from measurement of

24 bricks (mm) (From Table 5.10) T1

(mm) T2

(mm)

BS 3921 Individual brick deviations from

work size derived from

tolerances of 24 bricks

(1) (2) (3) (4) (5)

Len

gth

+ 2.41 0.4 215 5.9± = ±

0.25 215 3.7± = ±

3.125±

Wid

th

- 2.01

0.4 102.5 4.0± = ±

0.25 102.5 2.5± = ±

1.875±

Hei

ght

+ 3.4 0.4 65 3.2± = ± 0.25 65 2.0± = ±

1.875±

129

Therefore, from the comparisons of individual bricks dimensional tolerance

of prEN 771-1 and BS 3921 it could be observed that the dimensional tolerance for

individual bricks derived from BS tolerance for 24 bricks is more stringent than the

prEN 771-1 for both the T1 and T2 categories. Research results showed that the

mean deviations of the dimensions of bricks from the work size (Table 5.11, col. 2)

for length i.e. +2.41 mm was within the derived deviation of the BS (± 3 mm)

however the width and height had a deviation of –2.01 mm and +3.4 mm which

exceeded the deviations i.e. 1.875± for both width and height. Nevertheless, it

should be borne in mind that the strict dimensional deviations provided in the British

Standard was derived from the cumulative dimensions of 24 bricks. Moreover, these

deviations are restricted to bricks of the standard format specified in BS 3921.

Table 5.11 shows that the bricks investigated fulfil the requirements for category T1

of the dimensional tolerance specified in the prEN 771-1. The bricks however could

not satisfy the tolerance limit for category T2 due to the height exceeding the range

specified for the T2 category.

5.3.2 Dimension of Individual Brick for Length, Width and Height

Table 5.12 shows sample data with the mean, ranges, standard deviations,

and coefficient of variation for length, width and height of individual brick. The

mean for length, width and height were 216 mm (s =1.91 mm), 100 mm (s =1.12

mm) and 67 mm (s =1.91 mm) respectively and the normal values which is in the

middle third of the 33-percentile values were 216 to 218 mm for length, 98 to100

mm for width and 67 to 68 mm for height (Figure 5.8).

130

Table 5.12: Individual brick dimensions for length, width and height in all samples Length Width Height

Sample Mean

x

Range

R

Standard deviation

s

c.v. %

Mean

Range

R

Standard deviation

s

c.v. %

Mean

x

Range

R

Standard deviation

s

c.v. %

1 218.4 1.6 0.57 0.26 100.2 2.4 0.81 0.81 67.1 1.2 0.41 0.62 2 218.4 2.6 0.94 0.43 99.8 1.9 0.78 0.78 67.2 1.6 0.68 1.02 3 216.6 6.2 2.12 0.98 99.0 2.2 0.94 0.95 67.5 2.6 0.91 1.35 4 218.0 2.7 1.00 0.46 99.6 1.1 0.37 0.37 67.2 5.5 2.05 3.04 5 216.6 1.5 0.61 0.28 99.0 2.5 0.95 0.96 66.4 1.1 0.39 0.59 6 217.7 2.8 0.99 0.45 99.8 1.8 0.80 0.80 67.2 1.1 0.44 0.65 7 217.7 2.8 1.13 0.52 100.0 1.9 0.66 0.66 67.9 1.0 0.42 0.62

Batch 1

8 219.1 3.2 1.36 0.62 99.9 2.3 0.81 0.81 68.0 2.0 0.82 1.21 9 216.6 4.1 1.62 0.75 99.9 4.4 1.64 1.64 68.2 4.3 1.45 2.13

10 215.5 10.5 3.63 1.68 99.3 4.1 1.43 1.44 67.8 3.4 1.19 1.75 11 216.1 3.9 1.57 0.72 99.3 2.4 0.95 0.95 68.1 2.5 0.83 1.22 12 216.4 5.8 2.29 1.06 98.9 4.8 1.82 1.84 67.7 2.5 0.83 1.22 13 218.0 6.5 2.72 1.25 100.4 4.3 1.57 1.56 68.2 2.0 0.65 0.95 14 217.7 3.7 1.67 0.77 100.3 2.8 1.16 1.15 67.3 1.9 0.86 1.28 15 217.7 6.2 2.16 0.99 99.8 3.7 1.39 1.39 67.7 1.7 0.73 1.08 16 218.8 4.5 1.77 0.81 100.7 3.9 1.52 1.51 68.8 4.3 1.42 2.06 17 216.8 1.7 0.73 0.34 99.8 2.2 0.88 0.88 67.6 1.6 0.62 0.91 18 219.0 2.6 0.94 0.43 100.9 1.2 0.44 0.44 68.2 1.9 0.81 1.18 19 216.7 4.0 1.76 0.81 99.8 2.3 0.86 0.86 68.2 2.2 0.75 1.11 20 217.7 3.7 1.43 0.66 100.2 2.6 0.85 0.85 68.1 1.6 0.61 0.89 21 219.1 4.7 1.85 0.84 101.0 4.4 1.65 1.63 68.1 3.1 1.09 1.60 22 217.5 7.0 2.60 1.20 99.8 5.9 2.07 2.07 68.6 3.4 1.21 1.77 23 216.3 4.9 1.91 0.88 99.4 3.3 1.43 1.44 67.9 2.0 0.69 1.02

Batch 2

24 218.0 11.0 4.14 1.90 100.0 4.2 1.60 1.60 67.9 2.7 0.95 1.39

131

Table 5.12 (cont.): Brick dimensions for length, width and height in all samples. Length Width Height

Sample Mean

x

Range,

R

Standard deviation

s

c.v. % Mean

x

Range

R

Standard deviation

s

c.v. % Mean

x

Range

R

Standard deviation

s

c.v. %

25 215.7 2.1 0.98 0.46 99.7 2.3 0.89 0.89 67.2 1.1 0.37 0.55 26 214.6 2.5 0.98 0.46 99.5 1.7 0.71 0.71 66.9 1.0 0.40 0.60 27 215.1 2.2 0.89 0.42 99.8 3.2 1.22 1.22 67.1 2.0 0.67 1.00 28 214.7 3.3 1.19 0.55 99.9 1.7 0.73 0.73 67.1 1.0 0.34 0.51 29 215.4 2.3 0.80 0.37 99.7 2.2 0.79 0.79 67.4 0.6 0.25 0.38 30 216.3 2.3 0.82 0.38 100.5 1.8 0.60 0.60 67.7 0.8 0.34 0.51 31 214.7 3.9 1.33 0.62 99.4 3.3 1.13 1.14 67.4 2.6 1.03 1.52 32 215.7 2.2 0.79 0.37 100.3 2.1 0.74 0.74 67.5 1.5 0.53 0.79 33 215.2 3.1 1.26 0.59 99.4 2.3 0.97 0.97 67.4 2.9 0.94 1.40 34 215.5 2.8 1.21 0.56 100.0 0.9 0.32 0.32 67.2 1.6 0.57 0.85 35 215.1 1.8 0.72 0.34 99.0 3.0 1.13 1.15 67.0 0.4 0.11 0.17 36 215.1 2.2 0.75 0.35 98.7 1.3 0.43 0.43 67.1 1.8 0.58 0.86 37 216.1 2.3 0.80 0.37 99.8 3.0 1.08 1.08 67.0 1.1 0.38 0.57 38 215.0 1.5 0.51 0.24 99.2 1.4 0.54 0.54 66.8 1.0 0.38 0.57 39 214.8 1.4 0.57 0.26 99.6 1.4 0.61 0.62 67.0 0.6 0.20 0.30

Batch 3

40 215.2 2.2 0.94 0.44 100.2 1.4 0.49 0.49 67.1 1.3 0.44 0.65

132

Table 5.12 (cont.): Brick dimensions for length, width and height in all samples. Length Width Height

Sample

Mean x

Ranges

R

Standard deviation

s

c.v. %

Mean x

Ranges

R

Standard deviation

s

c.v. %

Mean x

Ranges

R

Standard deviation

s

c.v. %

41 216.4 1.6 0.54 0.25 100.2 1.8 0.65 0.65 67.7 1.4 0.51 0.75 42 216.2 3.4 1.24 0.57 99.8 2.8 1.03 1.03 67.5 1.4 0.49 0.72 43 215.6 2.7 1.02 0.48 99.6 3.0 1.24 1.24 67.4 1.2 0.40 0.60 44 215.1 3.5 1.46 0.68 98.9 4.3 1.64 1.66 67.1 1.9 0.74 1.10 45 215.1 3.5 1.27 0.59 98.7 3.3 1.15 1.17 67.3 1.7 0.66 0.97 46 215.7 3.3 1.12 0.52 99.4 3.2 1.18 1.19 67.4 1.6 0.62 0.93 47 215.7 3.8 1.30 0.60 99.1 2.5 1.02 1.03 66.6 2.8 1.06 1.59 48 216.2 4.9 1.81 0.84 99.2 3.2 1.32 1.33 67.6 2.9 1.12 1.66 49 216.9 5.7 2.63 1.21 100.2 4.4 1.93 1.93 67.4 1.6 0.71 1.05 50 214.6 3.2 1.18 0.55 99.0 1.7 0.62 0.62 67.0 2.2 0.71 1.06 51 216.8 6.2 2.04 0.94 100.0 3.2 1.10 1.10 67.5 1.9 0.74 1.10 52 217.0 6.9 2.37 1.09 99.7 2.2 0.79 0.79 67.0 3.3 1.06 1.59 53 215.8 4.1 1.56 0.72 100.0 1.1 0.40 0.40 68.3 2.1 0.82 1.21 54 215.4 1.6 0.59 0.27 99.5 3.1 1.00 1.00 67.2 1.1 0.37 0.55 55 216.1 2.1 0.72 0.33 100.3 1.2 0.40 0.40 67.4 1.7 0.61 0.90

Batch 4

56 216.3 1.5 0.58 0.27 99.8 1.4 0.55 0.56 67.5 0.6 0.27 0.40

133

0102030405060708090

209.

75-2

10.9

1

210.

91-2

12.0

7

212.

07-2

13.2

3

213.

23-2

14.3

9

214.

39-2

15.5

5

215.

55-2

16.7

0

216.

70-2

17.8

6

217.

86-2

19.0

2

219.

02-2

20.1

8

220.

18-2

21.3

4

221.

34-2

22.5

0

Individual length (mm)

Freq

uenc

y

Normal Curve

0102030405060708090

100

96.3

0-96

.96

96.9

6-97

.62

97.6

2-98

.28

98.2

8-98

.94

98.9

4-99

.60

99.6

-100

.26

100.

26-1

00.9

2

100.

92-1

01.5

8

101.

58-1

02.2

4

102.

24-1

02.9

0

102.

90-1

03.5

6

Individual width (mm)

Freq

uenc

y Normal curve

0

20

40

60

80

100

120

63.5

0-64

.21

64.2

1-64

.91

64.9

1-65

.62

65.6

2-66

.32

66.3

2-67

.03

67.0

3-67

.73

67.7

3-68

.44

68.4

4-69

.14

69.1

4-69

.85

69.8

5-70

.55

70.5

5-71

.26

Individual height (mm)

Freq

uenc

y

Normal curve

Figure 5.8: Histogram and normal curve for individual dimensions

of length, width and height of bricks

Control charts for the dimensions shows that all data points for the width

were lying within the upper and lower action line and showing less scatter about the

mean (Figure 5.9). All samples were then considered to represent the population

estimates for the width. For length and height, sample data lying outside the upper

and lower warning and action lines were ignored for the derivation of the population

mean.

216.4 mm1.91mm

. . 0.88 %Median= 216.2 mmMode= 215.0 mm

xsc v

===

Low <216 mm Normal 216–218 mm High >218 mm

Low < 98 mm Normal 98 – 100 mm High > 100 mm

Low < 67 mm Normal 67 – 68 mm High > 68 mm

99.7 mm1.12 mm

. . 1.12 %Median= 99.8 mmMode= 100 mm

xsc v

===

67.5 mm0.89 mm

. . 1.32 %Median= 67.4 mmMode= 67.0 mm

xsc v

===

134

214.0215.0216.0217.0218.0219.0220.0

0 10 20 30 40 50 60Sample

Len

gth

(mm

)M

ean

0.0

3.0

6.0

9.0

12.0

0 10 20 30 40 50 60

Sample

Len

gth

(mm

) R

ange

(a)

98,098,599,099,5

100,0100,5101,0101,5

0 10 20 30 40 50 60

Sample

Wid

th (m

m)

Mea

n

0,01,02,03,04,05,06,07,0

0 10 20 30 40 50 60

Sample

Wid

th (m

m)

Ran

ge

(b)

66,066,567,067,568,068,569,069,5

0 10 20 30 40 50 60

Sample

Hei

ght (

mm

)M

ean

0,01,02,03,04,05,06,0

0 10 20 30 40 50 60

Sample

Hei

ght (

mm

)R

ange

(c)

Figure 5.9: Control charts for mean values and ranges of samples for (a)

length (b) width and (c) height of bricks

The components of variances for samples from the different batches were

computed from the ANOVA. A single factor ANOVA was carried out on the

remaining samples after ignoring those outliers from the control charts. The

variances computed from the ANOVA were 1.98, 1.25 and 0.49 for length, width

and height respectively. Table 5.13 shows the comparisons of mean dimension from

results of this research with specified values of BS 3921. It could be seen that the

population mean dimensions of length i.e. 215 to 218 mm, width 99 to 101 mm and

height 67 to 68 mm were within the allowable dimensions of the BS (i.e. less than

the coordinating size for the respective length, width and height). Moreover,

individual measurements also showed that none of the bricks in the sample had

135

dimensions exceeding the specified coordinating size (Appendix A1, Table A1-1,

A1-2, A1-3)

Table 5.13: Mean dimensions of individual length, width and height of

bricks compared with British Standard (BS 3921:1985)

Mean dimensions (mm)

British standard Specification

High (upper 33-percentile)

Normal (middle 33-percentile)

Low (lower 33-percentile)

Population estimates @ 95 %

confidence (mm)

Work size (mm)

Coordinating size (mm)

Length

>218 216 – 218 < 216 215 – 218 215 225

Width >100 98 – 100 < 98 99 – 101 102.5 112.5

Height >68 67 – 68 < 67 67 – 68 65 75

5.4 Water Absorption

Table 5.14 shows specimens results for water absorption for all samples.

The descriptive statistics computed shows that the mean water absorption in

percentage was 11.23 with a standard deviation of 1.284 and c.v. of 11.43 %.

Table 5.14: Water absorption of specimens in each sample for facing bricks

Sample Water absorption of bricks (%)

1 10.6 10.2 10.9 12.7 9.5 11.6 10.8 10.6 13.7 10.5 2 8.4 13.4 10.4 8.8 9.5 11.9 10.5 8.0 11.6 12.1

Batch

1

3 10.5 11.0 11.2 11.6 10.6 11.4 10.8 13.0 12.3 11.1 4 11.6 12.6 10.7 10.8 11.6 12.0 10.8 11.3 13.4 10.6 5 11.8 12.9 12.2 13.8 11.1 10.4 12.4 11.2 12.4 10.9 6 10.8 13.1 12.4 12.4 10.9 11.5 10.0 11.9 11.3 11.2 7 12.0 11.5 10.9 11.6 11.7 12.3 12.2 13.0 13.0 11.9 8 12.4 10.4 10.1 12.4 11.6 10.7 12.0 11.5 12.3 10.5 9 11.9 12.7 11.2 9.7 11.6 11.9 11.1 12.8 13.2 12.0 10 12.0 10.4 11.6 10.0 11.7 12.8 10.3 9.4 12.2 13.6

Batch 2

11 13.1 11.5 12.7 12.1 11.0 12.3 12.2 11.1 11.8 11.5

136

Table 5.14 (cont.) 12 11.9 11.3 12.1 12.7 10.5 10.5 10.4 12.7 10.4 11.3 13 9.9 9.0 11.0 11.4 11.8 10.2 11.6 12.0 12.3 10.8 14 12.4 11.2 12.2 10.6 12.1 12.8 11.1 10.7 11.3 11.0 15 11.9 11.6 10.5 10.3 11.1 11.8 9.2 10.8 11.7 10.0 16 7.7 10.3 11.3 12.0 9.7 11.4 11.6 10.3 10.8 9.8 17 8.8 9.2 9.3 8.8 10.1 9.6 9.3 9.1 9.5 10.4 18 10.4 10.2 11.1 10.3 11.5 11.9 11.4 11.4 9.5 10.6

Batch 3

19 11.2 10.8 12.1 9.4 9.9 10.1 10.2 10.5 12.2 11.4 20 8.6 13.6 11.6 12.4 11.0 11.5 8.5 11.6 10.0 11.7 21 12.6 8.6 12.1 11.7 9.7 12.1 12.0 8.6 11.8 8.3 22 10.3 9.6 11.4 11.1 10.6 14.0 13.3 11.1 9.9 10.0 23 9.3 13.1 12.0 10.4 12.7 12.9 9.3 12.7 13.5 11.3 24 12.3 11.0 13.0 12.6 13.5 12.4 12.8 14.4 12.1 11.9 25 12.7 8.9 9.6 11.7 12.4 13.4 10.7 11.8 12.7 11.1 26 11.7 7.9 9.3 10.1 11.7 12.1 8.6 9.2 11.1 13.0

Batch 4

27 12.5 12.2 12.0 7.9 12.7 12.4 11.3 8.8 11.5 11.8 Descriptive Statistics Mean, x = 11.2 % Median = 11.4 % Mode = 12.3 % Standard deviation, s = 1.28 % Maximum = 14.4 % Minimum = 7.7 % Range, R = 6.7 % Coefficient of variation, c.v. = 11.44 %

The histogram with the normal curve superimposed to represent the data

distribution is shown in Figure 5.10.

010203040506070

7.55

-8.2

5

8.25

-8.9

5

8.95

-9.6

5

9.65

-10.

35

10.3

5-11

.05

11.0

5-11

.75

11.7

5-12

.45

12.4

5-13

.15

13.1

5-13

.85

13.8

5-14

.55

Absorption in percentage

Freq

uenc

y

Figure 5.10: The histogram and the normal curve fit for water


The 33-percentile values were computed from the normal curve. The middle

third of the distribution, which refers to the normal values of water absorption was

11 to 12 %. The control charts as shown in Figure 5.11 shows that sample 17 and

11.2 %1.28 %

. . 11.43%Median = 11.4 %Mode = 12.3 %

xsc v

===

Low < 11% Normal 11 – 12% High > 12%

Normal curve

137

24 were lying outside the upper and lower action line. Therefore, these two samples

were ignored in the determination of the population mean. The variance derived

from ANOVA was 1.53 with the standard deviation of 1.24 %. The population

mean for water absorption at 95 % confidence falls in the range of 10 to 12 %.

9,010,011,012,013,0

0 10 20 30

Sample

Wat

er A

bsrp

tion

(%)

Mea

n

0,02,04,06,08,0

0 10 20 30

Sample

Wat

er A

bsor

ptio

n (%

)R

ange

Figure 5.11: Control chart of mean values and ranges of samples for

water absorption of bricks

In most standards water absorption is often specified against compressive

strength to designate bricks classification. In conjunction with this classification the

bricks population under investigation have a mean compressive strengths of 40 to

over 50 N/mm2 with water absorption of 10 to12 %, appears to supersede the top

range of SW bricks meant for structural application in ASTM.

Table 5.15: Comparison of water absorption with limits specified by British

Standard and ASTM Water absorption %

British Standard (BS 3921) ASTM C 62 – 89a

Research results

at 95% confidence Engineering A Engineering B Grade

SW Grade MW

Grade NW

10 – 12 % ≤4.5 % ≤7.0 % Maximum

17 % Maximum 22 %

No limit

Comparison of the values for water absorption tests with limits specified in

BS and ASTM (Table 5.15) shows that water absorption of bricks for the

population in this study did not lie in the range of the Engineering A and B of the

BS. However, it can be seen that this range was within the requirements in ASTM

for bricks of the SW and MW category.

138

The British standard specifies bricks of high strength and low water

absorption for their Engineering bricks, which are meant for structural masonry.

Corresponding characteristic flexural strength to three levels of water absorption is

provided in BS 5628: Part 1 i.e. less than 7 %; between 7 % and 12 % and over 12

% to be used in designs (Table 5.16). In this respect, the water absorption

characterised by the bricks in this investigation relates to second level of water

absorption i.e. between 7 and 12 % to yield an estimated characteristic flexural

strength of 0.35 to 1.5 depending upon the mortar designation and plane of failure.

Table 5.16: Relationship between characteristic flexural strengths and levels

of water absorption (BS 5628 Pt. 1) Characteristic flexural strength , fkx N/mm2

Plane of failure parallel to bed joints

Plane of failure perpendicular to bed joints

Mortar designation

(i) (ii) and (iii) (iv) (i) (ii) and (iii) (iv)

Water absorption less than 7%

0.7 0.5 0.4 2.0 1.5 1.2

Between 7 % and 12 % 0.5 0.4 0.35 1.5 1.1 1.0

Over 12 % 0.4 0.3 0.25 1.1 0.9 0.8

A relationship between water absorption and porosity was developed for

bricks investigated in this research. The relation was a projection from results

obtained by Khalaf (2002) and is shown in Chapter VI.


The initial rate of suction for bricks in this investigation was computed based

on gross and net area of immersion. In the BS, IRS is determined based on gross

area of immersion without considering the reduced area due to perforations for cored

bricks. However, in the ASTM and AS/NZS the IRS for cored bricks is calculated

based on the net area of immersion i.e. the gross area less the area of perforations

139

Table 5.17 shows the results of IRS in the specimens for all samples. The

sample mean based on gross area of immersion was 1.6 kg/m2.min. with a standard

deviation of 0.49 kg/m2.min. and a c.v. of 29.6 %.

Table 5.17: Computed values for initial rate of suction of specimens

for facing bricks based on gross area of immersion Sample IRS kg/(m2.min.)

1 1.8 1.4 1.6 1.4 2.2 1.6 2.3 0.9 1.6 1.2 2 1.4 1.6 1.4 0.9 1.6 1.6 1.4 1.2 1.4 1.8

Batch

1

3 1.4 1.6 2.6 1.2 1.9 1.6 1.6 1.6 2.1 1.6 4 1.6 1.7 1.6 1.9 2.2 1.6 1.8 1.8 1.7 1.7 5 1.7 1.8 2.0 1.4 1.7 2.0 2.1 1.7 2.1 2.3 6 1.8 1.6 1.8 1.4 2.0 2.9 1.6 1.7 1.5 1.5 7 2.0 2.0 2.0 2.0 1.7 2.2 1.9 1.7 1.8 1.8 8 2.0 2.3 2.4 2.0 1.3 1.5 1.7 1.4 1.9 2.3 9 1.9 1.3 2.0 1.7 1.6 1.6 1.4 1.1 2.0 1.9 10 1.6 1.1 1.8 2.6 1.7 1.8 1.5 1.5 1.9 1.9

Batch 2

11 2.0 1.9 1.9 2.1 2.2 0.8 1.7 1.7 1.7 1.1 12 1.4 2.0 1.2 2.0 2.1 1.4 2.0 1.6 1.5 2.3 13 1.7 1.9 1.5 1.6 2.1 1.9 1.7 1.2 1.4 2.4 14 2.0 1.6 2.1 1.8 1.3 1.9 1.6 1.9 1.6 2.5 15 1.4 1.5 2.5 1.2 2.0 1.9 1.1 1.5 2.0 1.6 16 0.1 1.0 1.8 1.1 1.2 1.5 1.4 1.5 1.0 1.8 17 2.0 1.2 1.5 1.4 1.4 1.4 1.1 1.4 1.0 0.7 18 1.1 1.5 1.1 1.0 1.8 1.0 1.9 1.7 1.2 1.7

19 1.9 1.9 1.7 1.6 1.9 1.8 1.2 1.6 1.5 1.1 20 2.1 0.6 1.1 2.0 1.8 1.6 2.0 0.7 1.2 1.9 21 1.7 0.9 2.0 2.1 0.9 2.1 0.8 1.8 1.5 1.7 22 1.9 2.1 1.6 2.1 1.5 1.3 0.4 1.5 0.6 2.7 23 1.8 2.1 1.8 1.8 0.8 1.6 2.5 0.7 2.3 1.5 24 2.5 3.1 1.5 1.6 2.3 2.1 2.4 2.5 0.8 1.1 25 2.3 0.8 2.2 2.5 2.2 1.5 2.3 1.8 0.7 2.3 26 1.2 0.2 0.6 2.2 0.8 2.3 2.5 0.9 2.4 0.9

Batch 4

27 1.1 2.3 0.9 0.2 0.9 1.9 1.3 1.0 1.1 2.2 Descriptive Statistics Mean, x = 1.6 kg/(m2.min.) Median = 1.7 kg/(m2.min.) Mode = 2.3 kg/(m2.min.) Standard deviation, s = 0.49 kg/(m2.min.) Maximum = 3.1 kg/(m2.min.) Minimum =0.1 kg/(m2.min.) Range, R = 3.0 kg/(m2.min.) Coefficient of variation, c.v. = 29.6 %

The c.v. for IRS in the samples was almost 30.0 % and therefore the log-

normal probability curve was used to represent the data distribution. Figure 5.12

shows the histogram with the log-normal curve superimposed. The 33-percentile

140

values in the sample data were computed from the log-normal probability curve and

data in the middle third i.e. 1.0 to1.30 kg/m2.min. indicated normal values for IRS.

These values were within the limits of IRS denoted to produce good bond.

01020304050607080

0.14

- 0.

417

0.41

7 - 0

.694

0.69

4 - 0

.971

0.97

1 - 1

.248

1.24

8 - 1

.525

1.52

5- 1

.802

1.80

2 - 2

.079

2.07

9 - 2

.356

2.35

6 - 2

.633

2.63

3 - 2

.910

Initial rate of suction kg/(m2.min)

freq

uenc

y

Log-normalcurve

Figure 5.12: Histogram and normal curve fit for IRS based on


1.00

1.50

2.00

2.50

0 5 10 15 20 25 30

Sample

IRS

kg/(m

2 .min

)M

ean

0.00

1.00

2.00

3.00

0 5 10 15 20 25 30

Sample

IRS

kg/(m

2 .min

)R

ange

Figure 5.13: Control charts for means and ranges for IRS based on


The control charts of means and ranges (Figure 5.13) shows that some

samples were lying outside the control limits i.e. the upper and lower warning and

action lines. Therefore, these samples i.e. samples 4, 7, 16, 17, 22, 24, 26 and 27

were taken as not representative of the population and were ignored in the

determination of the population mean. The estimate of variance derived from

ANOVA for all data after ignoring the samples described above was 0.178. The

corresponding standard deviation was 0.422 kg/m2.min.and the population mean

ranging from 1.4 to 2.0 kg/m2.min i.e. at 95 % confidence (5 % reject).

2

2

2

2

1.6 / .min0.49 / .min

. . 30.0%1.7 / .min

mod 2.3 / .min

x kg ms kg mc vmedian kg m

e kg m

===

==

Low < 1.0 kg/m2.min Normal =1.0 – 1.30 kg/m2.min High > 1.30 kg/m2.min

141

ASTM specifies that bricks with IRS greater than 1.5 kg/m2.min should be

well wetted before laying and recommended that the wetting be carried out 3 to 24

hours before use. On the other hand there is no provision of IRS limits in the BS

3921:1985. However, a test method for determining IRS is included in the British

standard as this parameter is important for highly stressed masonry structures. In

prEN 771-1 the IRS values are only required in application where the work warrant

its use and in this respect the value should be declared by the manufacturer.

Although the normal values of IRS in the middle third distribution, ranged

from 1.0 to 1.3 kg/m2.min is within the recommended limit of the ASTM the upper

range of the 95 % confidence limits were higher than 1.5 kg/m2.min. Hence,

consideration for wetting of the bricks should be emphasised especially in

application where bond strength is critical.

Wetting bricks before laying is more critical in hot weather construction

since suction rate of bricks is influenced by the temperature of the bricks and the

surrounding temperature (Davidson, 1982). Warmer units will absorb more water

from the mortar and in addition, the water from mortar is evaporated at a faster rate.

For this reason, in hot weather construction, bricks with high suction rates (over 1.5

kg/m2.min) should be well wetted before laying. On this basis, the IRS should be

regarded as an important property of brick for this country, which experience hot

weather throughout the year.

Table 5.18 shows the results for IRS based on net area of immersion. The

mean IRS was 1.9 kg/m2.min, which showed a considerable increase of about 20 %

from the IRS determined by gross area of immersion. The ASTM considers this

factor and specified that the IRS should be calculated based on the net area of

immersion for perforated bricks while the AS/NZS 4456:1997 specifies both values

of IRS due to net and gross area of immersion.

142

Table 5.18: Computed values for initial rate of suction of specimens of

facing bricks based on net area of immersion

Sample IRS kg/(m2.min.)

1 2.11 1.65 1.89 1.66 2.60 1.86 2.67 1.10 1.90 1.36 2 1.64 1.90 1.62 1.11 1.90 1.92 1.63 1.37 1.63 2.17 3 1.64 1.90 3.01 1.37 2.23 1.91 1.90 1.91 2.43 1.91 4 1.90 1.96 1.93 2.18 2.62 1.88 2.13 2.08 1.97 1.99 5 1.95 2.08 2.38 1.62 1.99 2.38 2.48 2.05 2.50 2.74 6 2.14 1.83 2.06 1.65 2.35 3.43 1.89 2.00 1.74 1.74 7 2.40 2.33 2.33 2.30 1.98 2.53 2.29 2.00 2.12 2.12 8 2.37 2.65 2.82 2.41 1.49 1.71 1.96 1.62 2.24 2.71 9 2.23 1.48 2.35 1.97 1.85 1.88 1.70 1.31 2.30 2.26 10 1.92 1.31 2.11 3.07 1.98 2.06 1.78 1.80 2.22 2.18

Batch 1

11 2.35 2.19 2.27 2.42 2.60 0.89 2.01 2.04 2.02 1.26 12 1.67 2.34 1.39 2.39 2.42 1.59 2.34 1.86 1.73 2.73 13 2.02 2.28 1.71 1.88 2.44 2.19 1.99 1.40 1.67 2.81 14 2.38 1.93 2.43 2.09 1.55 2.22 1.87 2.25 1.87 2.94 15 1.59 1.71 2.94 1.40 2.38 2.21 1.24 1.75 2.35 1.89 16 0.17 1.21 2.07 1.27 1.35 1.70 1.60 1.75 1.17 2.11 17 2.37 1.44 1.80 1.65 1.69 1.70 1.27 1.70 1.16 0.83 18 1.32 1.73 1.34 1.17 2.17 1.23 2.28 1.98 1.39 2.02

Batch 3

19 2.19 2.17 2.03 1.91 2.22 2.13 1.44 1.93 1.76 1.29 20 2.45 0.68 1.28 2.29 2.09 1.89 2.32 0.79 1.35 2.19 21 2.02 1.06 2.29 2.49 1.11 2.50 0.89 2.16 1.80 1.98 22 2.25 2.44 1.90 2.53 1.78 1.49 0.45 1.73 0.68 3.19 23 2.08 2.46 2.07 2.11 0.96 1.86 3.00 0.85 2.73 1.78 24 2.97 3.59 1.81 1.92 2.71 2.52 2.78 2.92 0.98 1.28 25 2.66 0.94 2.57 2.92 2.55 1.70 2.68 2.07 0.82 2.66 26 1.45 0.22 0.71 2.60 0.99 2.71 2.93 1.06 2.77 1.04

Batch 4

27 1.24 2.66 1.04 0.28 1.04 2.19 1.52 1.20 1.30 2.59 Mean x = 1.933 kg/(m2.min.)

5.6 Density

Table 5.19 shows the results for the density test in the specimens for all

samples. The mean density from sample data was 1781.51 kg/m3 with a standard

deviation of 35.858 kg/m3 and a c.v. of 2.013 %.

143

Table 5.19: Density of specimens in each sample for facing bricks

Sample Density kg/m3

1 1761.03 1848.48 1777.78 1803.70 1770.37 1787.31 1868.00 1785.19 1793.48 1751.85 2 1751.80 1805.15 1748.12 1795.62 1804.51 1775.36 1791.97 1797.71 1834.59 1800.00

Batch

1 3 1794.57 1773.08 1671.33 1767.61 1792.59 1715.83 1759.69 1792.59 1812.50 1794.78 4 1776.60 1782.95 1731.06 1794.57 1775.74 1734.85 1781.48 1746.48 1802.33 1765.38 5 1785.27 1784.96 1757.64 1783.46 1780.85 1792.03 1755.47 1754.74 1721.01 1740.58 6 1781.69 1754.29 1800.75 1794.78 1752.67 1756.12 1780.14 1780.14 1779.70 1785.21 7 1705.15 1794.96 1771.74 1795.62 1778.52 1738.89 1750.35 1815.56 1747.33 1781.29 8 1847.73 1754.55 1770.21 1773.53 1760.31 1769.23 1757.86 1775.00 1759.85 1772.22 9 1782.48 1778.10 1786.86 1748.57 1789.78 1783.94 1749.29 1756.12 1789.05 1778.99

10 1773.91 1823.13 1784.44 1794.16 1771.18 1775.36 1831.58 1755.71 1774.64 1814.81

Batch 2

11 1797.81 1761.59 1778.99 1810.29 1805.88 1793.38 1820.44 1783.45 1819.12 1830.08 12 1802.17 1789.05 1822.39 1802.21 1795.59 1836.09 1774.64 1834.81 1800.73 1824.26 13 1783.94 1770.29 1784.67 1814.07 1820.90 1828.15 1807.41 1836.09 1843.28 1827.61 14 1856.72 1836.30 1805.15 1842.22 1756.83 1766.91 1813.33 1786.86 1822.06 1781.02 15 1796.27 1842.97 1764.93 1792.42 1813.85 1833.86 1771.64 1902.27 1747.76 1878.74 16 1851.16 1763.16 1763.70 1799.25 1749.62 1817.56 1784.09 1791.85 1787.97 1716.79 17 1766.92 1891.27 1775.56 1809.85 1751.82 1806.15 1762.12 1788.64 1761.65 1856.25 18 1834.38 1797.66 1767.65 1760.00 1773.33 1759.84 1840.94 1773.48 1817.32 1775.38

Batch 3

19 1733.82 1762.69 1817.69 1800.76 1754.74 1692.09 1800.00 1725.18 1739.42 1695.71 20 1784.44 1685.00 1696.40 1810.24 1793.02 1739.85 1770.00 1793.28 1755.56 1751.11 21 1768.15 1705.93 1742.96 1736.09 1716.18 1798.50 1754.55 1737.31 1790.15 1739.10 22 1829.46 1770.45 1743.61 1725.19 1760.00 1761.48 1739.10 1791.73 1747.37 1747.73 23 1821.54 1778.63 1738.35 1719.05 1765.12 1754.81 1758.02 1782.71 1738.35 1766.92 24 1783.58 1766.21 1789.84 1728.56 1792.77 1773.95 1720.93 1763.33 1788.46 1768.82 25 1767.45 1742.24 1748.89 1830.37 1803.45 1792.74 1810.54 1780.34 1811.22 1795.16 26 1756.83 1879.38 1795.56 1805.85 1741.94 1795.26 1761.12 1768.64 1759.74 1806.25

Batch 4

27 1836.83 1806.39 1805.15 1842.22 1726.54 1716.82 1797.33 1825.95 1802.17 1781.02 Descriptive Statistics Mean, x = 1781.51 kg/m3 Median = 1781.158 kg/m3 Mode = 1805.147 kg/m3 Standard deviation, s = 35.858 kg/m3 Maximum = 1902.273 kg/m3 Minimum =1671.329 kg/m3 Range, R = 230.944 kg/m3 Coefficient of variation, c.v. =2.013%

Figure 5.14 shows the histogram to represent data distribution. Assuming

that the data is normally distributed, the normal curve fit is analysed and the curve

superimposed on the histogram. From the normal curve the 33-percentile computed

from sample data shows the middle third distribution, which consists of the normal

values for density ranging from 1766 to 1795 kg/m3.

144

From Control charts for means and ranges of density (Figure 5.15), the

samples lying outside the upper and lower warning and action lines were ignored to

determine the population mean. A single factor ANOVA was carried out on the

remaining sample data to determine the components of variance in the samples

among the different batches. The variance determined from the ANOVA was 1114.0

with standard deviation of 33.38 kg/m3. The population mean neglecting the samples

outside the zones mentioned above, and with 95 % confidence limits was 1757

to1804 kg/m3. This value was higher than the average value of density i.e.1610

kg/m3 (Table 5.20) required for sound insulation purposes of the Building

Regulations of the United Kingdom.

01020304050607080

1670

.0-1

693.

1

1693

.1-1

716.

217

16.2

-173

9.3

1739

.3-1

762.

417

62.4

-178

5.5

1785

.5-1

808.

6

1808

.6-1

831.

718

31.7

-185

4.8

1854

.8-1

877.

918

77.9

-190

1.0

1901

.0-1

924.

1

Density kg/m3

Freq

uenc

y

Figure 5.14: Histogram and normal curve fit for density of

bricks

1740

1760

1780

1800

1820

0 5 10 15 20 25 30

Sample

Den

sity

kg/

m3

Mea

n

0

50

100

150

200

0 10 20 30

Sample

Den

sity

kg/

m3

Ran

ge

Figure 5.15: Control charts for mean values and ranges of samples for

density of bricks

3

3

3

3

1781.51 /35.86 /

1781.16 /mod 1805.15 /. . 2.013%

x kg ms kg mmedian kg m

e kg mc v

==

==

=

Low < 1767 kg/m3 Normal 1767 – 1795 kg/m3 High > 1795 kg/m3

145

Table 5.20: Density of bricks for sound insulation in walls and walls

with plaster finish for (Building regulations of the UK)

Wall

Plaster finish

Material

and dimensions

(mm)

Thickness

(mm)

Specified

weight at least (kg/m2) includes

finish

Number of sides

Type

Average

density of brick to be

used (kg/m3)

Solid wall Brick size mm 65 x 102.5 x 215

215

375

2

2

Lightweight

Gypsum

1610

1610

Cavity wall

255

415

2

2

Lightweight

Gypsum

1970

1970

Density of brick has been given more emphasis recently in masonry

standards. The prEN 771-1 included density as a requirement especially to identify

the acoustic property of a brick. A brick wall with thickness 102.5 mm could give a

sound reduction index of 46 dB (Curtin, et. al). Table 5.21 shows the typical sound

insulation values of masonry walls with respect to its thickness and weight.

Loudness of 40 to 50 dB is considered as faint to moderate loudness suitable for an

average home and general to private office (Drysdale, et.al).

Table 5.21: Typical sound insulation values of masonry walls

(Curtin, et. al)

Material and construction

Thickness (mm)

Weight (kg/m2)

Approximate sound

reduction index (dB)


215

415

49.5


102.5

220

46

146

5.7 Efflorescence

The results in the test for efflorescence were based on the 4 samples

(1 sample in each batch). Every brick in a sample of 10 bricks were examined for

efflorescence after the test. Based on visual examination of the exposed surfaces for

all the samples in the 4 batches no deposits of salts or any other effects of

efflorescence such as powdering or flaking could be detected.

5.8 Soluble Salt Content

Bricks were tested for the presence of acid soluble sulphates and water-

soluble salts of calcium, magnesium, potassium and sodium. Table 5.22 shows the

content of soluble salt in the samples from the various batches and the maximum

limit of salt content provided by BS 3921:1985 for the category of low salt.

Table 5.22: Percentage of soluble salts in samples from all batches Sample Calcium Sodium Potassium Magnesium Sulphate

1 0.013 0.003 0.003 0.003 0.07

Batch

1 2 0.014 0.002 0.003 0.002 0.07 3 0.003 0.004 0.006 0.002 0.09 4 0.006 0.002 0.009 0.003 0.06

Batch 2

5 0.016 0.003 0.007 0.006 0.09 6 0.010 0.001 0.003 0.004 0.02 7 0.007 0.003 0.006 0.003 0.09 8 0.011 0.002 0.005 0.004 0.04

Batch 3

9 0.007 0.001 0.003 0.003 0.02 10 0.008 0.002 0.004 0.003 0.02 11 0.009 0.002 0.004 0.003 0.02

Batch 4

12 0.010 0.002 0.004 0.005 0.02

Mean, x % 0.010 0.002 0.005 0.003 0.05 Sample standard deviation, s 0.004 0.0006 0.002 0.001 0.03

c.v. % 40.0 30.0 40.0 33.3 60.0

BS 3921:1985 0.3 % 0.03 % 0.03 % 0.03 % 0.50 %

147

The results indicated that the percentage of salts i.e. calcium, sodium,

magnesium, potassium and sulphate in the bricks were very small in comparisons

with the limits for the category of Low salt content as defined in BS 3921:1985.

The c.v. in the test for sulphate was considerably high which was about

60 %. The reason for this was most probably due to the test method used. Sulphate

was determined by the gravimetric method, which is confined to relatively high

sulphate content. The method was also considered as rather complicated and this

may contributed to the significant variability in the results (Brachtel, 2003).

The results of salt content compared with the European Standard prEN 771-1

also showed that the bricks investigated had very low salt content. The combined

content of sodium and potassium in the bricks from this research was 0.007 %,

which is very much below the maximum limits provided in prEN 771-1 for category

S1 (0.17 %) and S2 (0.06 %). Similarly, with a mean percentage of 0.003,

magnesium was also below the specified maximum limit i.e. 0.08 and 0.03 for

category S1 and S2 respectively. Thus the bricks fit into the category of application

of S1 and S2 as defined in the European Standard; S1 is for normal exposure and S2

is suitable for prolonged saturation applications.

CHAPTER 6

APPLICATIONS OF RESEARCH FINDINGS

6.1 Relationship of Aspect Ratio to Compressive Strength

In masonry construction bricks are normally laid on the bed face, which yield

the greatest compressive strength compared to if laid in the stretcher or header faces.

A relationship between the compressive strengths of units and their aspect ratio (h/t),

was proposed through the research findings described in the earlier chapters. The

compressive strengths are related to h/t as described by the following relationship:

16.35 58.17f x= − + …(6.1)

Where,

f = compressive strengths of a brick (N/mm2)

x =aspect ratio (height to thickness ratio, h/t).

The above relationship was obtained by the best-fit line with a regression

coefficient of R2 = 0.998 (Figure 6.1)

149

f = -16.353x + 58.168R2 = 0.998

0

10

20

30

40

50

0 0.5 1 1.5 2 2.5 3 3.5

Height to thickness ratio, h/tC

ompr

essi

ve st

reng

th, f

N/m

m2

Figure 6.1: Relationship between compressive strength

and h/t ratio of bricks.

Equation 6.1 can be used to estimate compressive strength of a brick for

various h/t ratio greater than 0.7 but less than 3.2. The dimensions h and t are

defined accordingly to the orientation of bricks in a brick laying (Figure 6.2), where

h = height of the brick normal to the loading axis,

t = smaller dimension of the loaded surface area.

W= direction of loading on wallW

WW

(c)

t

h

(b)(a) t

hh

t

(b) bed face (c) stretcher face

Figure 6.2: Orientation of bricks in a brick laying (a) header face

150

The estimated strength provides useful information to manufacturers as well

as designers in assessing the compressive strength of a brick when loaded in the

various orientations without conducting any tests, as yet giving an important data for

use in preliminary design or strength assessment. The proposed relationship is also

convenient to users where facilities for testing are not available at hand. The

applicability of the proposed estimated relationship is only valid under the following

conditions:

• The bricks are fired clay bricks.

• Percentage of perforations is about 20 %

• The aspect ratio h/t must lie between 0.7 to 3.2

It should be noted that the estimated compressive strengths for bricks loaded

on the bed face as derived in equation 6.1 is based on gross loaded area whereby

perforated areas were ignored. This tends to yield a smaller compressive strength

than if computed using net area. Hence, the prediction given by this formula for

perforated bricks tested on bed face is conservative.

Conventionally the compressive strength test provides the strength of bricks

when loaded on bed face. The relationship between the compressive strength of

bricks when loaded on the bed face and in other test orientations are considered

important for design and preliminary assessment purposes.

An attempt is made to establish this relationship, based on the research

findings described in previous chapters and illustrated below. The compressive

strength of bricks when loaded on the bed face is used as a standard measure as it is

the only available data in any compressive test.

Assuming fb, fs and fh are the corresponding compressive strength of bricks

in the bed, stretcher and header faces. Substituting the values of fb and fs as 46.1 and

34.7 N/mm2 for compressive strengths of bricks in this research, therefore a ratio of

fs : fb can be established as shown in equation 6.2.

151

34.7 0.7546.1

s

b

ff

= = …(6.2)

or,

0.75s bf f= …(6.3)

Similarly, the compressive strength due to loading on the header face (fh=

5.5 N/mm2) can be derived in terms of fb as shown in equation 6.4.

5.5 0.1246.1

h

b

ff

= = …(6.4)

fh = 0.12 fb …(6.5)

For fired clay bricks the ratio of compressive strength for bricks tested on the

stretcher face to bed face, 0.75s

b

ff

= . The ratio of compressive strength for bricks

tested on the header face to the bed face, 0.12h

b

ff

= .

This is a convenient method of projecting the test results to other orientations

in the absence of laboratory facilities, and also acts as a guide to some preliminary

design work. It is to be noted, however, that the relationship of equation 6.3 and 6.5,

are valid provided that the conditions stated earlier are satisfied.

6.2 Relationship of Water Absorption to Porosity and Compressive Strength

Recent investigation on brick porosity and water absorption (Khalaf, 2002)

has indicated that there is a relationship between water absorption, porosity and

compressive strength. Table 6.1 shows the results of bricks compressive strength,

water absorption and porosity obtained by Khalaf.

152

Table 6.1: Relationship between bricks compressive strength, water

absorption and porosity (Khalaf, 2002)

Brick Type

Full-brick compressive

strength (N/mm2)

Water absorption of brick units BS 3921

(5-hr boil) (%)

Porosity of brick lumps by

vacuum (%)

Class B engineering 92 6.0 14.85 Clay 10 hole 81 6.2 16.75 Clay 3 slot and 8 hole 68 5.8 17.39 Clay frogged common 39 12.9 25.04 Granite - 2.63 6.15

Using the results from Table 6.1 the graphs as shown in Figure 6.3 and 6.4

were plotted to show the relationship of water absorption to porosity and

compressive strength of bricks respectively.

y = 0.74x - 6.05R2 = 0.9348

468

101214

14 16 18 20 22 24 26

Porosity (%)

Wat

er a

bsor

ptio

n,%

( 5

-hr

boili

ng)

Figure 6.3: Relationship of water absorption with porosity

from Table 6.1

f = -4.97x + 161.96R2 = 0.9497

020406080

100

14 16 18 20 22 24 26

Porosity (%)

Full-

bric

k co

mpr

essi

vest

reng

th, f

(N/m

m2 )

Figure 6.4: Relationship of porosity with compressive strength

from Table 6.1

The relationship of water absorption with porosity (Figure 6.3) was used to

determine the porosity of the bricks in this investigation as shown in equation 6.6

153

0.74 6.05y x= − …(6.6)

Where,

y = water absorption (%)

x = porosity (%)

Substituting y = 11.2% i.e. the mean water absorption for the bricks in this

investigation, in equation 6.6, the porosity, x = 23 %

The relationship of porosity with compressive strength is shown in Figure

6.4. Knowing the porosity the compressive strength could be derived from the

relationship as described by equation 6.7

4.97 161.96f x= − + …(6.7)

Where,

f = compressive strength (N/mm2)

x = porosity ( %)

Substituting the porosity, x = 23 % in equation 6.7, the compressive strength

computed was 47.65 N/mm2, which was close to the value of the mean compressive

strength in this research i.e. 46.1 N/mm2. Thus it could be assumed that the bricks in

this investigation had a porosity of about 23 %. However it is to be noted that the

porosity derived in this equation was based on results of 20 mm bricks lumps.

CHAPTER 7

CONCLUSIONS AND RECOMMENDATIONS

FOR FURTHER WORK

7.1 Conclusions

The conclusions are divided into two sections i.e. the general conclusions

and the detailed conclusions. The general conclusions dealt with properties found in

the present Malaysian standards (MS 76 Part 2:1972) i.e. compressive strengths,

water absorption, dimensional tolerance and soluble salt content. The detailed

conclusions consist of other aspects of the properties evaluation arising from

comparisons conducted with other international standards and the varying test

methods and measurements used by these standards. The section also contains new

properties consisting of initial rate of suction and density useful for the development

of masonry standards.

7.2 General Conclusions

The mean compressive strength of facing bricks falls in the range of

40 N/mm2 to 50 N/mm2 and common bricks 30 N/mm2 to 40 N/mm2. The bricks fall

within the higher range of compressive strengths specified in Malaysian Standard

MS 76:1972 and therefore regarded as load bearing units.

155

The mean water absorption of the bricks investigated was 10 % to 12 %,

which lied outside the specified limits for Engineering A (≤4.5 %) and Engineering

B (≤7 %) of the Malaysian/British Standard.

The results on the overall dimensions of 24 bricks showed that both the

length and the width fall within the permissible tolerance of the Malaysian

Standard/British Standard. However, the height exceeded the Malaysian Standard/

British Standard tolerance limit considerably by about 37 mm. Therefore, the

category of dimensional deviations in existing Malaysian standard, which was based

on the BS overall measurement of 24 bricks need to be modified accordingly.

The content of calcium, magnesium, potassium, sodium and sulphate in the

bricks was very negligible and thus they fall under the durability designation of

“Low” (L) of soluble salt content as per BS 3921:1985. In accordance to European

Standard, the bricks could be applied even for the worst condition of construction

application i.e. S2, which is meant for masonry structures subjected to prolonged

wet situation.

7.3 Detailed Conclusions

7.3.1 Compressive strengths

The range of mean compressive strength obtained in the bricks surpass the

minimum value i.e. 20.7 N/mm2 specified for compressive strength of facing brick

in ASTM C216-90a to be used in SW (severe weathering) regions. Under Singapore

Standard SS 103:1974, the bricks could be categorised as the First Grade bricks.

Considerable reduction of compressive strength was observed when bricks

were tested in the different orientations. When tested on the stretcher face the

compressive strength was approximately 60 % to 90 % of the compressive strength

tested on bed face. On the header face the compressive strength was further reduced

156

to about 10 % to 15 % of the strength tested on bed face. Hence, compressive

strength should be indicated with the brick orientation for testing.

Compressive strength of bricks is affected by curing conditions before

testing. Dry bricks show higher compressive strengths than wet bricks. The

compressive strength of bricks evaluated in the tests was based on saturated

condition, therefore, providing conservative values by about 15 to 20 %.

Additionally, the compressive strength was computed based on gross area, further

reducing the compressive strength by approximately 20 %.


Although the bricks researched could not satisfy the requirements for the

water absorption in the Malaysian Standard (MS 76:1972), the values were well

within the requirements provided in ASTM for Grade SW and MW bricks with

water absorption limits of 17 % and 22 % respectively.

Malaysian bricks tend to have high water absorption, typically greater than

10 %, and this can be explained by the limestone content in the soil. This is not a

characteristic of British soil, therefore water absorption in British bricks are usually

lower.

The water absorption of the bricks investigated corresponds to the second

level of the characteristic flexural strength of BS 5628: Part 1, denoted by strengths

of 0.35 to 1.5 N/mm2, which depend on the mortar designation and the plane of

failure. These values are required in the design of masonry structures.

The relation of water absorption to porosity showed that the porosity of the

bricks in this investigation was about 23 %. Compressive strength of bricks could be

related to their porosity and this relationship would be useful for a preliminary

estimation of compressive strength.

157


Comparison of results with the recent European Standard shows that the

bricks investigated satisfy the category of T1 of prEN 771-1.

7.3.4 Initial Rate of Suction

The bricks in this investigation had a mean initial rate of suction of 1.4 to 2.0

kg/m2.min, which fall under the high range of IRS. Ideally, the value of IRS should

be between 0.25 to 1.5 kg/min.m2 for the development of appropriate bond strength

between the bricks and the mortar interface. ASTM recommends that bricks with

IRS exceeding 1.5 kg/min.m2 should be wetted before laying. The bricks indicted

high values of IRS hence requiring pre-wetted surface before laying in order to

optimise bonding upon laying on to mortar. This is considered more critical in hot

weather construction since hot bricks will absorb more water and the water in mortar

will be depreciated at a faster rate with high temperature.

The range of IRS values of 1.4 to 2.0 kg/m2.min demonstrated by the bricks

in this investigation was determined using gross area i.e. without reducing the area

of immersion by the area of perforations. The IRS calculated using net area of

immersion shows an IRS value higher than about 18 % if based on gross area. The

BS 3921:1985 computed the IRS based on gross area while the ASTM and AS/NZS

use the net area. It is therefore significant that IRS values be clearly indicated for

both cases of calculation to avoid confusion. Therefore, specification for IRS values

should be denoted as IRSgross or IRSnet depending on the surface area of immersion.

158

7.3.5 Soluble Salt Content

The soluble salt content for all the minerals under investigations i.e. calcium,

sodium, potassium, magnesium and sulphate were all below the maximum limits

specified in the British Standard. This justifies the reason why salt does not appear

on the brick surfaces in the efflorescence test. The effects of sulphate have been

given a considerable attention in existing standards, however this is not the case for

EN 771-1. The European standard considered the sulphate action a complex matter

to be dealt with in the national design codes. Sodium and potassium has been

analysed as a combined effect in the EN, with maximum values of 0.17 %

depending on the application category. In this case the research results of 0.007 %

does not exceed the recommended percentage of the EN. The percentage of sulphate

present in the bricks was 0.05 %. This value is much below the maximum of 0.5 %

allowed for in the BS 3921.

7.3.6 Density

The density of the bricks in this investigation is within the range of 1757

kg/m3 to 1804 kg/m3. Previous works imply that the bricks in this range use in a

102.5 mm thick wall could give a sound insulation of 40 to 50 dB (Curtin et al.,

1995) which is considered as faint to moderate loudness suitable for an average

home and general to private office (Drysdale et al., 1994). The density of the bricks,

also suffice the requirements for sound insulation specified in the building

regulations in the United Kingdom.

7.4 Recommendations for Further Work

The bricks properties reported herein was based on a production from a

single manufacturer of clay bricks. Future studies should include other

manufacturers of clay bricks in order to achieve results representative of the entire

159

population of bricks in the country. The results representing the whole population

would characterise local production and therefore useful in the development of

national standards. Recommendations for future research should include the

following:

(i) Sampling should be obtained from a larger number of manufacturers

across the country for a more representative estimate of the properties and to

include various types of bricks in local production.

(ii) In order to get a more comprehensive relationship of the compressive

strengths with the bricks aspect ratio (h/t), bricks samples should comprise

other formats and configurations to include a wider range of bricks types.

In this research, bricks were generally tested in accordance to the British

standard procedure. However, procedures from other standards were also looked

into and regarded as more reliable and accurate. Some recommendations to be

considered in the testing methods for future studies include:

(i) Investigation on the density of bricks should be determined for both

the dry and ambient condition.

(ii) Evaluation of water absorption by the 5-hr boiling test involving the

use of small brick lumps as specimen instead of the normal whole brick may

be considered. This new method would certainly be more economical

because less fuel would be needed in boiling the small specimen. Moreover,

the handling of experiments would be more convenient with small specimens

especially in testing that implicate a large amount of samples as experienced

in this research. Further, it was claimed that this new method could produce

results that are more accurate.

(iii) In the preparation of specimens for the tests of water absorption and

IRS, BS 3921 procedure for attaining constant mass when drying bricks in

the oven is by heating the bricks for at least 48 hrs. The ASTM and

Australian standard monitor the change of mass at specified intervals. Bricks,

160

which are recently manufactured, normally have very small moisture content.

Thus, they may not need too long a duration for example the 48 hours

assumed to attain constant mass. Therefore, by monitoring the weight loss

may reduce the time of heating and consequently economise on the use of

energy. For this matter, it is recommended that the AS/NZS 4456 or the

ASTM C 67 be adopted in the laboratory procedure for attaining constant

mass of bricks.

(iv) In the test for IRS, standard method should incorporate ways of

ensuring a consistent 3 mm immersion during the test. This could be helpful

in attaining more precise results.

REFERENCES

American Concrete Institute, Detroit (1992). “Specifications for Masonry Structures

ACI 530.1-92/ASCE 6-92/TMS 602-92, Reference manual.

American Society for Testing Materials (1990), “Standard Specification for Facing

Brick” (Solid Masonry Units Made from Clay or Shale). United States of

America, ASTM C 216-90a.

American Society for Testing Materials (1989), “Standard Specification for Hollow

Brick” (Hollow Masonry Units Made from Clay or Shale). United States of


American Society for Testing Materials (1990), “Standard Specification for Building

Brick” (Solid Masonry Units Made from Clay or Shale). United States of


American Society for Testing Materials (1991), “Standard Test Methods of

Sampling and Testing Brick and Structural Clay Tile”. United States of America,

ASTM C 67-90a.

Beall, Christine (1993). “Masonry design and detailing.” Third Edition. New York.

McGraw-Hill Inc.

Bland, J. A. (1985). “Statistics for construction students.” London: Construction

Press.

162

Brachtel, G. “Water-soluble and acid-soluble sulphate content of heavy products.”

[Online] Available http://www.fh-koblenz.de/fachbereiche/fbker/f-und-e-

engl.html, April 6, 2003.

British Standards Institution (1985). “British Standard Code of Practice for use of

Masonry, Part 1. Structural Use of unreinforced masonry.” London, BS 5628

British Standards Institution (1985). “British Standard Code of Practice for use of

Masonry, Part 2. Structural Use of reinforced and Prestressed masonry.”

London, BS 5628

British Standards Institution (1985). “British Standard Specification for Clay

Bricks.” London, BS 3921

British Standards Institution (1991). “Guide to Statistical Interpretation of Data.”

London, BS 2846: Part 1

British Standards Institution (2000). “ Specification for masonry units (draft

candidate harmonised standard).” London, Draft: pr EN 771-1

Chatfield, C. (1978). “Statistics for technology.” London: Chapman and Hall.

Curtin, W.G., Shaw, G., Beck J. K. and Bray W.A. (1995). “Structural Masonry

Designers Manual.” Second Edition. London: Blackwell Science Ltd.

Davidson, J. I. (1982). “Effect of temperature on brick suction.” Journal of Testing

and Evaluation (ASTM) Vol. 10, No.3, pp81 – 82.

Drysdale, R.G., Hamid, A.A. and Baker, L.R. (1994). “Masonry Structures

Behaviour and Design.” Prentice Hall.

Experimental Building Station (Department of Construction) (1976). “Bond

Strength in Masonry.” Australian Governor Publishing Service.

163

Grimm, C.T. (1975). “Strength and related properties of brick masonry.” Journal of

The Structural Division. Technical Publications ASCE.

Grimm, C. T. (1988). “Statistical Primer for Brick Masonry.” Masonry: Materials,

Design, Construction, and Maintenance, pp. 169-192.

Grimm, C. T. (1996). “Clay Brick Masonry Weight Variation.” Journal of

Architectural Engineering, Vol. 2, No. 4, pp. 135-137

Hammer, M. J. and Hammer M. J. Jr. (1996). “Water & Wastewater Treatment.”

Singapore: Prentice Hall.

Hendry, A.W. (2001). “Masonry walls: materials and constrution”. Construction and

building Materials, 15. 323-330. Elsevier.

Hendry, A.W., Sinha, B.P., Davies S.R. (1981). “An introduction to load bearing

brickwork design.” U.K.: Ellis Horwood Limited.

Khalaf, F. M. and DeVenny, A. S. (2002). “New Tests for Porosity and Water

Absorption of Fired Clay Bricks.” Journal of Material in Civil Engineering.

Kennedy, J. B. and Neville A. M. (1985). “Basic Statistical methods for engineers

and scientist”. New York: Harper & Row Publishers.

Lenczner, D. (1972). “Elements of Load-bearing Brickwork”. Oxford, New York,

Toronto, Sydney, Braunschweig.: Pergamon Press,

Loveday, R. (1969). “Statistics A second Course in Statistics.” Cambridge, London,

New York, Melbourne: Cambridge University Press.

Montgomery, D. C. (2001). “Design and analysis of experiments.” 5 th. Edition.

John Wiley & Sons.

164

Morton, J. (1986). “The design of laterally loaded walls.” TGV Publications.

Morton, J. (1987). “Limit state philosophy Partial safety factors and the design of

walls for compression and shear.” TGV Publications.

Paradine, C. G. and Rivett, B. H. P. (1960). “ Statistical Methods for Technologists.”

England: English Universities Press.

Singapore Institute of Standard and Industrial Research (1974). “Specification for

Burnt Clay and Shale bricks.” (Singapore Standard 103:1974)

Standard Australia and Standard New Zealand (1997). “Masonry units and

Segmental pavers- Methods of test.” (AS/NZS 4456.0- 4456.18:1997)

Standards Association of Australia (1984). “Clay Building Bricks.” (AS 1225-1984)

Standards Institution of Malaysia (1972). “Specification for Bricks And Blocks Of

Fired Brickearth, Clay Or Shale.” (MS 76 Part 2).

Surej, R. K., Fazio, P. and Feldman, D. (1998). “Comparative Study of Durability

Indices For Clay Bricks.” Journal Of Architectural Engineering.

Surej, R. K., Fazio, P. and Feldman, D. (1998). “Development of New Durability

Index For Clay Bricks.” Journal Of Architectural Engineering.

Triola, M. F. (1989). “Elementary Statistics.” Fourth Edition. New York: The

Benjamin/Cummings.

Weldon, K. L. (1986). “Statistics A conceptual approach.” New Jersey: Prentice-

Hall.

APPENDICES

A 1

RESULTS OF TESTS SPECIMENS

FOR DIMENSIONAL TOLERANCE OF

INDIVIDUAL BRICKS

167 Table A1-1: Individual measurement for length

Sample Length 1 218.00 218.60 217.55 218.50 218.85 219.10 2 218.45 220.20 217.70 218.35 218.30 217.60 3 217.05 219.45 216.90 213.30 215.15 217.65 4 218.60 219.55 216.90 217.90 218.20 217.00 5 216.20 217.20 217.45 215.95 216.35 216.25 6 219.10 217.90 217.45 218.30 217.00 216.30 7 217.40 216.90 216.60 218.75 217.00 219.40

Batch 1

8 220.60 217.40 219.85 218.30 220.35 217.95 9 215.75 218.00 217.85 216.50 217.85 213.90 10 214.50 220.45 214.25 218.40 215.60 210.00 11 217.10 214.50 217.20 216.10 217.85 214.00 12 213.55 217.25 219.35 218.30 214.75 214.90 13 217.20 220.65 219.00 215.30 221.20 214.70 14 217.70 216.10 216.30 219.80 216.50 219.60 15 219.45 217.80 220.55 217.00 214.40 216.85 16 221.30 217.25 218.00 219.25 216.80 220.30 17 217.00 215.75 215.95 217.35 217.20 217.40 18 218.35 217.70 220.25 218.50 219.50 219.50 19 217.80 218.30 214.35 217.95 217.00 214.55 20 217.25 217.00 217.25 217.30 220.65 217.00 21 220.00 220.70 216.00 217.70 220.55 219.35 22 218.25 218.50 214.15 221.15 214.80 218.10 23 214.95 214.95 214.35 219.25 216.50 217.75

Batch 2

24 218.25 209.75 220.30 220.75 220.00 218.75 25 217.00 214.90 215.10 217.00 215.20 215.25 26 215.00 214.70 213.40 213.50 215.25 215.85 27 214.75 215.50 214.25 215.85 216.20 214.00 28 215.00 215.60 212.70 214.70 216.00 214.00 29 215.60 214.65 216.90 215.35 214.85 215.25 30 215.00 216.25 217.00 215.75 217.25 216.30 31 215.30 214.00 215.00 216.80 214.25 212.90 32 215.20 215.00 215.65 215.25 217.15 216.00 33 215.75 216.30 213.30 215.45 214.00 216.35 34 216.90 214.15 214.70 216.95 215.35 214.65 35 215.25 215.55 216.00 215.45 214.25 214.25 36 215.00 215.00 213.85 215.75 216.00 215.00 37 215.50 216.55 217.30 216.00 216.00 215.00 38 215.15 215.00 215.25 215.00 214.00 215.45 39 215.40 214.25 215.00 214.65 214.00 215.30

Batch 3

40 216.10 214.35 214.45 215.25 214.40 216.50 41 216.60 216.60 215.70 216.35 217.25 216.00 42 215.50 216.85 218.00 214.65 215.45 216.95 43 214.75 214.85 216.20 215.00 215.6 217.40 44 216.20 213.55 214.75 216.10 213.25 216.70 45 213.75 215.10 214.05 215.70 217.25 214.70 46 216.50 217.25 215.75 214.00 215.40 215.25 47 216.50 215.00 215.75 217.75 214.00 215.30 48 218.50 217.75 216.00 213.65 216.40 214.75 49 215.55 214.60 215.15 215.65 220.30 220.25 50 215.95 212.75 215.10 214.10 214.00 215.50 51 214.25 216.60 215.75 220.40 216.8 217.25 52 220.95 216.00 216.60 216.00 214.10 218.35 53 215.95 216.75 216.70 212.75 216.00 216.85 54 215.45 215.45 216.00 214.40 215.00 215.85 55 216.25 215.25 216.40 215.55 216.10 217.30

Batch 4

56 216.95 215.50 216.00 216.25 216.00 216.95

168 Table A1-2: Individual measurement for width

Sample Width 1 100.75 100.2 100.3 98.8 101.2 100.1 2 99.85 101 99.3 100.4 99.1 99.1 3 99.2 99.85 99.35 97.7 98 99.9 4 99.8 100.1 99.8 99.65 99.05 99.4 5 99.3 98 100.5 98.25 99.4 98.3 6 100.1 100.7 99.35 100.75 99 99 7 99.35 100 99.9 99.9 99.45 101.2

Batch 1

8 101.1 99.55 99.7 98.85 100.6 99.65 9 98.20 102.50 100.75 100.00 100.00 98.15 10 98.30 101.80 97.70 99.80 99.25 99.00 11 100.05 98.35 100.35 99.75 99.50 98.00 12 97.60 100.00 101.15 100.00 98.00 96.35 13 99.65 102.15 101.35 100.00 101.45 97.85 14 101.75 99.00 99.65 101.25 99.15 100.80 15 100.95 100.50 101.35 99.60 97.65 98.95 16 102.65 99.55 98.80 101.10 100.10 102.20 17 100.65 98.65 99.85 100.85 98.95 99.65 18 101.10 100.85 101.30 100.75 100.10 101.25 19 100.50 100.90 98.65 100.00 99.25 99.25 20 100.00 99.00 99.95 100.25 101.60 100.50 21 102.00 102.30 98.40 100.00 102.75 100.75 22 101.00 100.50 98.45 102.70 96.80 99.40 23 98.75 98.00 98.00 101.25 99.50 100.95

Batch 2

24 98.75 98.80 99.25 99.55 102.95 100.50 25 100.75 98.50 99.40 100.60 99.10 100.05 26 100.10 98.85 98.80 99.10 99.80 100.50 27 99.90 100.55 99.30 100.75 100.75 97.60 28 100.00 100.75 99.25 99.55 100.75 99.10 29 99.20 99.25 100.90 100.25 98.75 99.65 30 99.55 100.55 100.20 100.30 101.35 100.75 31 97.60 99.15 100.00 100.85 99.90 98.80 32 99.85 99.50 100.45 99.75 101.55 100.50 33 99.65 100.45 98.50 100.50 98.25 99.00 34 100.35 100.25 99.75 100.10 99.50 100.00 35 100.00 98.80 100.30 98.25 99.50 97.30 36 99.25 99.00 98.55 98.75 98.65 98.00 37 100.25 100.50 101.30 98.30 99.45 99.10 38 99.50 99.65 99.25 99.65 99.00 98.25 39 100.50 99.25 99.15 99.15 99.25 100.25

Batch 3

40 100.35 100.25 99.75 99.55 100.15 100.95 41 101.10 100.00 99.80 99.30 100.60 100.60 42 100.10 100.55 100.30 97.75 100.25 99.70 43 98.95 98.00 100.95 98.70 100.45 100.75 44 99.25 97.50 97.00 100.20 98.15 101.25 45 98.35 98.30 97.45 99.30 100.75 98.20 46 100.25 100.30 99.70 97.15 99.25 99.90 47 99.75 99.75 99.25 100.25 98.00 97.75 48 100.00 100.25 98.50 97.50 100.65 98.00 49 99.55 99.20 98.45 98.85 102.50 102.85 50 99.20 98.75 99.65 98.00 99.60 98.85 51 98.80 99.95 99.25 102.00 99.95 100.20 52 100.75 99.30 99.65 99.60 98.60 100.50 53 99.85 100.25 99.25 100.15 99.90 100.35 54 99.70 101.00 99.50 99.70 97.95 99.00 55 100.75 99.55 100.25 100.30 100.50 100.25

Batch 4

56 99.70 100.00 100.50 99.10 100.25 99.25

169

Table A1-3: Individual measurement for height.

Sample Height 1 67.10 67.10 67.75 66.60 66.70 67.25 2 66.75 67.80 67.80 67.90 66.30 66.85 3 69.05 67.20 67.40 66.75 66.50 67.80 4 69.40 67.00 63.95 66.10 69.25 67.45 5 66.20 66.40 65.90 66.60 66.10 67.00 6 67.50 66.75 67.45 67.65 67.00 66.60 7 67.50 67.30 68.20 68.25 68.30 67.90

Batch 1

8 67.50 67.30 69.30 67.75 68.75 67.45 9 67.85 67.65 71.00 67.80 68.00 66.75 10 67.20 68.50 68.00 69.20 68.25 65.80 11 68.10 67.00 68.30 67.50 69.45 68.00 12 67.35 67.65 69.10 67.40 67.90 66.60 13 67.20 68.05 68.25 68.35 68.00 69.20 14 67.95 66.20 66.35 67.95 66.95 68.10 15 68.50 67.75 68.45 66.85 67.60 66.85 16 68.70 66.75 71.00 69.25 69.15 68.00 17 67.00 68.55 67.55 67.50 66.95 68.05 18 68.95 67.25 68.80 67.50 67.85 69.10 19 69.25 67.05 68.00 68.75 68.00 68.00 20 68.75 67.90 68.75 67.75 68.25 67.20 21 68.65 69.10 66.00 68.15 68.55 68.05 22 69.90 69.25 67.95 68.55 66.50 69.25 23 66.75 68.25 68.75 67.75 68.15 67.50

Batch 2

24 68.25 66.10 67.75 68.00 68.75 68.50 25 67.65 67.20 67.00 67.50 67.15 66.60 26 67.15 67.25 66.65 66.25 67.00 67.25 27 67.00 67.20 66.85 67.50 68.00 66.00 28 67.00 67.25 66.50 67.00 67.50 67.25 29 67.15 67.20 67.75 67.45 67.70 67.30 30 67.55 67.95 68.00 67.95 67.25 67.30 31 66.75 66.00 68.30 67.90 68.55 66.70 32 67.25 67.25 67.75 67.00 68.50 67.50 33 67.65 67.50 66.00 67.25 66.85 68.85 34 67.80 67.00 67.75 67.35 66.25 67.20 35 67.20 67.00 67.00 67.00 66.85 67.00 36 66.75 66.25 68.00 67.00 67.25 67.05 37 67.00 67.35 67.60 66.75 67.00 66.55 38 66.60 67.45 66.55 67.15 66.75 66.50 39 66.75 67.00 66.75 66.95 67.00 67.30

Batch 3

40 67.75 67.00 66.50 67.25 66.75 67.25 41 67.30 68.00 67.55 68.35 68.00 67.00 42 67.70 67.55 68.00 66.60 67.50 67.80 43 67.45 67.15 67.50 66.80 68.00 67.55 44 67.60 66.35 66.50 68.25 66.70 67.35 45 66.80 67.50 66.85 67.20 68.50 66.85 46 67.80 67.80 67.90 66.35 67.75 67.00 47 67.80 65.95 67.65 65.00 66.30 66.75 48 69.25 68.25 67.75 66.35 67.50 66.35 49 66.70 66.90 67.00 67.00 68.25 68.25 50 68.25 66.10 67.10 66.85 66.70 67.20 51 66.30 67.00 67.90 68.20 67.60 68.15 52 68.55 67.35 65.25 66.75 67.10 67.05 53 67.75 68.95 69.25 68.80 67.20 67.75 54 67.00 67.35 67.70 67.25 66.60 67.25 55 67.25 67.00 67.75 67.25 66.85 68.50

Batch 4

56 67.25 67.25 67.20 67.80 67.75 67.50

A 2

RESULTS OF TEST SPECIMENS

FOR DENSITY OF BRICKS

171

Brick Weight (mo) Weight after Immersed Volume (V) Density (Da) identification as received 2 hrs soaking (m1) weight (m2) V=(m1-m2)*1000 mo/V*1,000,000

(gm) (gm.) (gm) mm3 kg/m3 51 2295 2630 1270 1360000 1687.50 27 2450 2590 1270 1320000 1856.06 48 2475 2620 1270 1350000 1833.33 67 2351 2650 1300 1350000 1741.48 32 2545 2630 1280 1350000 1885.19 6 2410 2600 1260 1340000 1798.51

19 2435 2470 1220 1250000 1948.00 22 2415 2610 1260 1350000 1788.89 50 2477 2690 1310 1380000 1794.93

Sam

ple

1

9 2545 2600 1250 1350000 1885.19 36 2435 2690 1300 1390000 1751.80 44 2455 2640 1280 1360000 1805.15 43 2325 2570 1240 1330000 1748.12 64 2460 2670 1300 1370000 1795.62 38 2400 2600 1270 1330000 1804.51 45 2450 2680 1300 1380000 1775.36 62 2455 2670 1300 1370000 1791.97 30 2355 2560 1250 1310000 1797.71 70 2440 2620 1290 1330000 1834.59

Sam

ple

2

66 2430 2630 1280 1350000 1800.00 85 2315 2520 1230 1290000 1794.57 92 2305 2530 1230 1300000 1773.08 41 2390 2680 1250 1430000 1671.33 96 2510 2770 1350 1420000 1767.61 87 2420 2650 1300 1350000 1792.59 43 2385 2680 1290 1390000 1715.83 91 2270 2490 1200 1290000 1759.69 42 2420 2640 1290 1350000 1792.59 81 2465 2690 1330 1360000 1812.50

Sam

ple

3

99 2405 2650 1310 1340000 1794.78 82 2505 2760 1350 1410000 1776.60 88 2300 2510 1220 1290000 1782.95 95 2285 2540 1220 1320000 1731.06 84 2315 2530 1240 1290000 1794.57 98 2415 2650 1290 1360000 1775.74 86 2290 2540 1220 1320000 1734.85 100 2405 2640 1290 1350000 1781.48 97 2480 2740 1320 1420000 1746.48 90 2325 2530 1240 1290000 1802.33

Sam

ple

4

89 2295 2560 1260 1300000 1765.38 2 2303 2510 1220 1290000 1785.27

52 2374 2600 1270 1330000 1784.96 3 2531 2790 1350 1440000 1757.64 1 2372 2630 1300 1330000 1783.46 9 2511 2740 1330 1410000 1780.85

14 2473 2690 1310 1380000 1792.03 6 2405 2630 1260 1370000 1755.47

50 2404 2610 1240 1370000 1754.74 10 2375 2600 1220 1380000 1721.01

Sam

ple

5

7 2402 2660 1280 1380000 1740.58 46 2530 2750 1330 1420000 1781.69 49 2456 2710 1310 1400000 1754.29 55 2395 2600 1270 1330000 1800.75 4 2405 2630 1290 1340000 1794.78

56 2296 2520 1210 1310000 1752.67 57 2441 2700 1310 1390000 1756.12 12 2510 2740 1330 1410000 1780.14 48 2510 2740 1330 1410000 1780.14 54 2367 2620 1290 1330000 1779.70

Sam

ple

6

5 2535 2760 1340 1420000 1785.21 26 2319 2560 1200 1360000 1705.15 69 2495 2720 1330 1390000 1794.96 33 2445 2700 1320 1380000 1771.74 30 2460 2710 1340 1370000 1795.62 35 2401 2630 1280 1350000 1778.52 29 2504 2780 1340 1440000 1738.89 31 2503 2770 1340 1430000 1750.35 59 2451 2660 1310 1350000 1815.56 37 2289 2520 1210 1310000 1747.33

Sam

ple

7

22 2476 2710 1320 1390000 1781.29

172

66 2439 2610 1290 1320000 1847.73 28 2509 2780 1350 1430000 1754.55 34 2496 2740 1330 1410000 1770.21 21 2412 2630 1270 1360000 1773.53 67 2306 2540 1230 1310000 1760.31 32 2530 2780 1350 1430000 1769.23 58 2461 2700 1300 1400000 1757.86 45 2343 2570 1250 1320000 1775.00 68 2411 2660 1290 1370000 1759.85

Sa

mpl

e 8

94 2233 2450 1190 1260000 1772.22 16 2442 2660 1290 1370000 1782.48 10 2436 2650 1280 1370000 1778.10 14 2448 2650 1280 1370000 1786.86 20 2448 2700 1300 1400000 1748.57 21 2452 2670 1300 1370000 1789.78 11 2444 2650 1280 1370000 1783.94 24 2449 2700 1300 1400000 1749.29 18 2441 2660 1270 1390000 1756.12 7 2451 2660 1290 1370000 1789.05

Sam

ple

9

23 2455 2670 1290 1380000 1778.99 15 2448 2660 1280 1380000 1773.91 22 2443 2630 1290 1340000 1823.13 19 2409 2600 1250 1350000 1784.44 17 2458 2660 1290 1370000 1794.16 13 2446 2670 1289 1381000 1771.18 9 2450 2670 1290 1380000 1775.36 8 2436 2600 1270 1330000 1831.58 5 2458 2700 1300 1400000 1755.71

12 2449 2680 1300 1380000 1774.64

Sam

ple

10

3 2450 2650 1300 1350000 1814.81 83 2463 2660 1290 1370000 1797.81 82 2431 2660 1280 1380000 1761.59 79 2455 2680 1300 1380000 1778.99 86 2462 2650 1290 1360000 1810.29 72 2456 2640 1280 1360000 1805.88 88 2439 2630 1270 1360000 1793.38 77 2494 2670 1300 1370000 1820.44 91 2479 2700 1310 1390000 1783.45 94 2474 2650 1290 1360000 1819.12

Sam

ple

11

89 2434 2600 1270 1330000 1830.08 92 2487 2690 1310 1380000 1802.17 84 2451 2650 1280 1370000 1789.05 81 2442 2620 1280 1340000 1822.39 93 2451 2640 1280 1360000 1802.21 90 2442 2640 1280 1360000 1795.59 75 2442 2610 1280 1330000 1836.09 80 2449 2670 1290 1380000 1774.64 95 2477 2650 1300 1350000 1834.81 96 2467 2660 1290 1370000 1800.73

Sam

ple

12

76 2481 2640 1280 1360000 1824.26 50 2444 2680 1310 1370000 1783.94 68 2443 2690 1310 1380000 1770.29 73 2445 2680 1310 1370000 1784.67 53 2449 2660 1310 1350000 1814.07 64 2440 2640 1300 1340000 1820.90 49 2468 2680 1330 1350000 1828.15 52 2440 2660 1310 1350000 1807.41 54 2442 2640 1310 1330000 1836.09 55 2470 2660 1320 1340000 1843.28

Sam

ple

13

61 2449 2630 1290 1340000 1827.61 74 2488 2700 1360 1340000 1856.72 56 2479 2710 1360 1350000 1836.30 57 2455 2680 1320 1360000 1805.15 60 2487 2670 1320 1350000 1842.22 71 2442 2700 1310 1390000 1756.83 51 2456 2710 1320 1390000 1766.91 65 2448 2630 1280 1350000 1813.33 66 2448 2690 1320 1370000 1786.86 58 2478 2710 1350 1360000 1822.06

Sam

ple

14

59 2440 2670 1300 1370000 1781.02

173

14 2407 2620 1280 1340000 1796.27 19 2359 2520 1240 1280000 1842.97 1 2365 2610 1270 1340000 1764.93

24 2366 2580 1260 1320000 1792.42 18 2358 2540 1240 1300000 1813.85 17 2329 2470 1200 1270000 1833.86 13 2374 2600 1260 1340000 1771.64 15 2511 2640 1320 1320000 1902.27 20 2342 2600 1260 1340000 1747.76

Sam

ple

15

16 2386 2510 1240 1270000 1878.74 22 2388 2550 1260 1290000 1851.16 11 2345 2590 1260 1330000 1763.16 6 2381 2600 1250 1350000 1763.70 5 2393 2600 1270 1330000 1799.25 4 2327 2580 1250 1330000 1749.62 3 2381 2590 1280 1310000 1817.56 9 2355 2560 1240 1320000 1784.09 2 2419 2650 1300 1350000 1791.85 7 2378 2600 1270 1330000 1787.97

Sam

ple

16

8 2352 2640 1270 1370000 1716.79 31 2350 2600 1270 1330000 1766.92 47 2383 2510 1250 1260000 1891.27 44 2397 2660 1310 1350000 1775.56 35 2389 2570 1250 1320000 1809.85 36 2400 2620 1250 1370000 1751.82 45 2348 2550 1250 1300000 1806.15 39 2326 2580 1260 1320000 1762.12 40 2361 2580 1260 1320000 1788.64 29 2343 2590 1260 1330000 1761.65

Sam

ple

17

32 2376 2520 1240 1280000 1856.25 46 2348 2520 1240 1280000 1834.38 37 2301 2510 1230 1280000 1797.66 40b 2404 2630 1270 1360000 1767.65 26 2376 2630 1280 1350000 1760.00 41 2394 2640 1290 1350000 1773.33 30 2235 2470 1200 1270000 1759.84 38 2338 2490 1220 1270000 1840.94 27 2341 2570 1250 1320000 1773.48 25 2308 2490 1220 1270000 1817.32

Sam

ple

18

28 2308 2540 1240 1300000 1775.38 54 2358 2590 1230 1360000 1733.82 56 2362 2570 1230 1340000 1762.69 53 2363 2520 1220 1300000 1817.69 50 2359 2530 1220 1310000 1800.76 68 2404 2630 1260 1370000 1754.74 67 2352 2640 1250 1390000 1692.09 52 2322 2510 1220 1290000 1800.00 57 2398 2650 1260 1390000 1725.18 58 2383 2620 1250 1370000 1739.42

Sam

ple

19

61 2374 2670 1270 1400000 1695.71 64 2409 2620 1270 1350000 1784.44 62 2359 2670 1270 1400000 1685.00 70 2358 2660 1270 1390000 1696.40 55 2299 2450 1180 1270000 1810.24 65 2313 2500 1210 1290000 1793.02 59 2314 2530 1200 1330000 1739.85 63 2301 2520 1220 1300000 1770.00 66 2403 2590 1250 1340000 1793.28 69 2370 2590 1240 1350000 1755.56

Sam

ple

20

71 2364 2590 1240 1350000 1751.11 74 2387 2620 1270 1350000 1768.15 84 2303 2550 1200 1350000 1705.93 82 2353 2600 1250 1350000 1742.96 76 2309 2560 1230 1330000 1736.09 85 2334 2560 1200 1360000 1716.18 96 2392 2590 1260 1330000 1798.50 94 2316 2550 1230 1320000 1754.55 91 2328 2580 1240 1340000 1737.31 79 2363 2580 1260 1320000 1790.15

Sam

ple

21

78 2313 2560 1230 1330000 1739.10

174

90 2360 2510 1220 1290000 1829.46 73 2337 2550 1230 1320000 1770.45 93 2319 2560 1230 1330000 1743.61 89 2329 2590 1240 1350000 1725.19 77 2288 2500 1200 1300000 1760.00 80 2378 2620 1270 1350000 1761.48 88 2313 2560 1230 1330000 1739.10 79 2383 2580 1250 1330000 1791.73 81 2324 2560 1230 1330000 1747.37

Sam

ple

22

86 2307 2540 1220 1320000 1747.73 61 2368 2510 1210 1300000 1821.54 60 2330 2530 1220 1310000 1778.63 58 2312 2550 1220 1330000 1738.35 57 2319 2590 1240 1350000 1717.78 56 2277 2500 1210 1290000 1765.12 54 2369 2610 1260 1350000 1754.81 53 2303 2540 1230 1310000 1758.02 52 2371 2570 1240 1330000 1782.71 51 2312 2550 1220 1330000 1738.35

Sam

ple

23

50 2297 2530 1230 1300000 1766.92 40 2349 2520 1220 1300000 1806.92 41 2380 2530 1210 1320000 1803.03 42 2395 2530 1230 1300000 1842.31 43 2379 2580 1210 1370000 1736.50 44 2400 2500 1250 1250000 1920.00 45 2348 2600 1230 1370000 1713.87 46 2316 2530 1220 1310000 1767.94 47 2361 2580 1230 1350000 1748.89

Sam

ple

24

39 2368 2590 1230 1360000 1741.18 20 2427 2640 1260 1380000 1758.70 21 2419 2650 1290 1360000 1778.68 22 2378 2620 1230 1390000 1710.79 23 2309 2450 1190 1260000 1832.54 24 2333 2510 1210 1300000 1794.62 25 2317 2490 1200 1290000 1796.12 26 2311 2530 1220 1310000 1764.12 27 2389 2570 1240 1330000 1796.24 28 2385 2580 1250 1330000 1793.23

Sam

ple

26

29 2359 2590 1240 1350000 1747.41 10 2432 2640 1270 1370000 1775.18 11 2511 2660 1290 1370000 1832.85 12 2378 2610 1230 1380000 1723.19 13 2319 2430 1180 1250000 1855.20 14 2293 2510 1210 1300000 1763.85 15 2317 2470 1200 1270000 1824.41 16 2401 2540 1190 1350000 1778.52 17 2370 2590 1240 1350000 1755.56 18 2325 2560 1240 1320000 1761.36

Sam

ple

27

19 2369 2597 1220 1377000 1720.41

A 3

RESULTS OF TESTS SPECIMENS FOR

INITIAL RATE OF SUCTION OF BRICKS

176

Sample 1

Brick identifica

tion

Dry mass

(md) gm

Wet mass

(mw) gm

length (mm)

l

Width (mm)

b

Immersed area

(mm2) Agross

Immersed area

(mm2) Anet

IRSgross 1000(mw – md)/Agross

kg/m2.min

IRSnet 1000(m2 –m1)/Anet

kg/m2.min

16 2445 2485 221.15 100.75 22280.86 18905.86 1.795 2.116

2 2390 2420 216.50 98.80 21390.20 18015.20 1.403 1.665

11 2415 2450 218.30 99.70 21764.51 18389.51 1.608 1.903

4 2370 2400 216.05 98.30 21237.72 17862.72 1.413 1.679

9 2435 2485 221.45 102.25 22643.26 19268.26 2.208 2.595

17 2430 2465 220.05 100.75 22170.04 18795.04 1.579 1.862

19 2440 2490 220.10 100.10 22032.01 18657.01 2.269 2.680

3 2435 2455 217.55 98.80 21493.94 18118.94 0.930 1.104

7 2415 2450 217.10 100.00 21710.00 18335.00 1.612 1.909

8 2410 2435 216.60 99.80 21616.68 18241.68 1.157 1.370

Sample 2 1 2380 2410 216.55 99.55 21557.55 18182.55 1.392 1.650

12 2420 2455 217.95 99.75 21740.51 18365.51 1.610 1.906

10 2485 2515 218.60 99.65 21783.49 18408.49 1.377 1.630

18 2430 2450 216.30 97.95 21186.59 17811.59 0.944 1.123

6 2410 2445 217.00 99.80 21656.60 18281.60 1.616 1.914

15 2465 2500 216.30 99.15 21446.15 18071.15 1.632 1.937

5 2460 2490 217.50 99.65 21673.88 18298.88 1.384 1.639

20 2410 2435 217.50 99.15 21565.13 18190.13 1.159 1.374

14 2370 2400 217.75 99.65 21698.79 18323.79 1.383 1.637

13 2370 2410 217.50 99.90 21728.25 18353.25 1.841 2.179

Sample 3

35 2410 2440 217.30 99.20 21556.16 18181.16 1.39 1.650

69 2420 2455 217.35 99.70 21669.80 18294.80 1.62 1.913

63 2435 2490 216.95 99.25 21532.29 18157.29 2.55 3.029

37 2400 2425 216.40 99.25 21477.70 18102.70 1.16 1.381

68 2430 2470 208.50 101.20 21100.20 17725.20 1.90 2.257

40 2410 2445 217.00 99.25 21537.25 18162.25 1.63 1.927

29 2410 2445 217.25 99.65 21648.96 18273.96 1.62 1.915

41 2415 2450 217.10 99.60 21623.16 18248.16 1.62 1.918

71 2440 2485 218.10 100.05 21820.91 18445.91 2.06 2.440

39 2440 2475 216.95 99.35 21553.98 18178.98 1.62 1.925

Sample 4 42 2420 2455 217.10 100.10 21731.71 18356.71 1.61 1.907

82 2505 2542 219.50 101.50 22279.25 18904.25 1.66 1.957

98 2403 2439 218.50 100.35 21926.48 18551.48 1.64 1.941

92 2299 2338 214.10 98.40 21067.44 17692.44 1.85 2.204

89 2288 2336 215.75 99.85 21542.64 18167.64 2.23 2.642

81 2447 2482 218.50 100.5 21959.25 18584.25 1.59 1.883

85 2306 2344 214.80 97.65 20975.22 17600.22 1.81 2.159

41 2364 2403 218.15 101.25 22087.69 18712.69 1.77 2.084

88 2292 2327 214.05 98.00 20976.90 17601.90 1.67 1.988

100 2399 2436 217.50 100.60 21880.50 18505.50 1.69 1.999

177

Sample 5

Brick identifica

tion

Dry mass

(md) gm

Wet mass

(mw) gm

length (mm)

l

Width (mm)

b

Immersed area

(mm2) Agross

Immersed area

(mm2) Anet


kg/m2.min


kg/m2.min

99 2400 2436 218.00 100.00 21800.00 18425.00 1.65 1.954

91 2265 2302 214.10 97.95 20971.10 17596.10 1.76 2.103

97 2472 2516 218.20 99.70 21754.54 18379.54 2.02 2.394

90 2318 2347 214.15 98.30 21050.95 17675.95 1.38 1.641

84 2306 2340 214.75 93.90 20165.03 16790.03 1.69 2.025

95 2280 2323 214.50 99.05 21246.23 17871.23 2.02 2.406

86 2281 2326 215.50 99.00 21334.50 17959.50 2.11 2.506

87 2414 2452 216.95 100.50 21803.48 18428.48 1.74 2.062

96 2500 2548 220.75 102.30 22582.73 19207.73 2.13 2.499

43 2378 2430 218.60 102.20 22340.92 18965.92 2.33 2.742

Sample 6 20 2444 2484 218.50 100.65 21992.03 18617.03 1.82 2.149

19 2450 2484 219.25 100.02 21929.39 18554.39 1.55 1.832

76 2439 2477 217.10 100.00 21710.00 18335.00 1.75 2.073

15 2410 2440 217.20 98.90 21481.08 18106.08 1.40 1.657

17 2434 2478 218.25 101.00 22043.25 18668.25 2.00 2.357

51 2295 2338 215.70 68.5 14775.45 11400.45 2.91 3.772

61 2540 2575 217.70 100.45 21867.97 18492.97 1.60 1.893

11 2391 2428 217.45 100.05 21755.87 18380.87 1.70 2.013

16 2425 2457 217.30 99.85 21697.41 18322.41 1.47 1.746

78 2415 2447 217.55 99.70 21689.74 18314.74 1.48 1.747

Sample 7

74 2407 2451 216.85 99.50 21576.58 18201.58 2.04 2.417

79 2449 2493 219.75 101.25 22249.69 18874.69 1.98 2.331

80 2466 2510 219.55 101.20 22218.46 18843.46 1.98 2.335

62 2447 2490 218.30 100.80 22004.64 18629.64 1.95 2.308

75 2375 2411 217.00 98.95 21472.15 18097.15 1.68 1.989

73 2264 2310 214.90 99.5 21382.55 18007.55 2.15 2.554

72 2300 2341 214.50 98.50 21128.25 17753.25 1.94 2.309

77 2401 2438 217.00 100.25 21754.25 18379.25 1.70 2.013

71 2295 2334 217.05 99.80 21661.59 18286.59 1.80 2.133

60 2446 2485 217.45 99.60 21658.02 18283.02 1.80 2.133

Sample 8

49 2464 2508 217.60 100.60 21890.56 18515.56 2.01 2.376

9 2483 2533 219.70 101.20 22233.64 18858.64 2.25 2.651

10 2304 2357 219.40 100.95 22148.43 18773.43 2.39 2.823

46 2489 2535 220.60 102.10 22523.26 19148.26 2.04 2.402

1 2435 2462 216.40 98.80 21380.32 18005.32 1.26 1.500

56 2328 2359 216.10 98.9 21372.29 17997.29 1.45 1.722

52 2370 2406 217.15 99.75 21660.71 18285.71 1.66 1.969

2 2304 2333 215.65 97.50 21025.88 17650.88 1.38 1.643

14 2456 2498 218.75 101.05 22104.69 18729.69 1.90 2.242

3 2502 2554 220.75 102.40 22604.80 19229.80 2.30 2.704

178

Sample 9 Brick

identification

Dry mass

(md) gm

Wet mass

(mw) gm

length (mm)

l

Width (mm)

b

Immersed area

(mm2) Agross

Immersed area

(mm2) Anet


kg/m2.min


kg/m2.min

7 2420 2461 217.30 99.75 21675.68 18300.68 1.89 2.240

4 2430 2457 216.75 99.40 21544.95 18169.95 1.25 1.486

50 2358 2401 218.00 99.00 21582.00 18207.00 1.99 2.362

5 2497 2534 218.95 100.95 22103.00 18728.00 1.67 1.976

6 2372 2406 217.30 99.65 21653.95 18278.95 1.57 1.860

57 2483 2518 217.75 100.95 21981.86 18606.86 1.59 1.881

55 2412 2443 215.25 100.00 21525.00 18150.00 1.44 1.708

54 2412 2436 216.30 100.00 21630.00 18255.00 1.11 1.315

48 2506 2550 221.00 101.85 22508.85 19133.85 1.95 2.300

12 2493 2536 220.75 101.35 22373.01 18998.01 1.92 2.263

Sample 10 58 2446 2482 217.60 101.75 22140.80 18765.80 1.63 1.918

94 2240 2263 210.00 98.25 20632.50 17257.50 1.11 1.333

35 2398 2437 217.75 100.00 21775.00 18400.00 1.79 2.120

29 2503 2562 220.75 102.50 22626.88 19251.88 2.61 3.065

33 2445 2482 219.25 100.50 22034.63 18659.63 1.68 1.983

34 2495 2534 219.75 101.50 22304.63 18929.63 1.75 2.060

21 2411 2444 219.90 99.25 21825.08 18450.08 1.51 1.789

69 2496 2530 219.50 101.20 22213.40 18838.40 1.53 1.805

26 2318 2359 217.95 99.70 21729.62 18354.62 1.89 2.234

37 2289 2328 214.25 98.35 21071.49 17696.49 1.85 2.204

Sample 11

30 2458 2502 218.35 101.00 22053.35 18678.35 2.00 2.356

68 2412 2452 218.30 98.65 21535.30 18160.30 1.86 2.203

32 2543 2587 221.25 103.05 22799.81 19424.81 1.93 2.265

31 2502 2549 220.50 103.95 22920.98 19545.98 2.05 2.405

28 2509 2559 220.80 102.55 22643.04 19268.04 2.21 2.595

66 2439 2455 214.75 98.85 21228.04 17853.04 0.75 0.896

67 2306 2342 214.40 98.20 21054.08 17679.08 1.71 2.036

22 2477 2515 220.75 99.60 21986.70 18611.70 1.73 2.042

45 2333 2369 214.65 97.75 20982.04 17607.04 1.72 2.045

59 2451 2474 216.00 99.65 21524.40 18149.40 1.07 1.267

Sample 12

22 2443 2473 213.50 99.00 21136.50 17761.50 1.42 1.689

18 2443 2486 215.50 100.55 21668.53 18293.53 1.98 2.351

17 2459 2484 214.95 98.80 21237.06 17862.06 1.18 1.400

12 2449 2493 216.00 100.50 21708.00 18333.00 2.03 2.400

24 2449 2494 217.25 101.00 21942.25 18567.25 2.05 2.424

3 2449 2478 214.30 100.00 21430.00 18055.00 1.35 1.606

10 2436 2479 215.25 100.75 21686.44 18311.44 1.98 2.348

9 2452 2486 215.00 100.00 21500.00 18125.00 1.58 1.876

19 2409 2440 213.25 99.25 21165.06 17790.06 1.46 1.743

20 2449 2500 217.00 101.50 22025.50 18650.50 2.32 2.735

179

Sample 13 Brick

identification

Dry mass

(md) gm

Wet mass

(mw) gm

length (mm)

l

Width (mm)

b

Immersed area

(mm2) Agross

Immersed area

(mm2) Anet


kg/m2.min


kg/m2.min

15 2448 2485 215.40 100.00 21540.00 18165.00 1.72 2.037

23 2456 2498 216.00 100.45 21697.20 18322.20 1.94 2.292

7 2452 2483 215.00 99.50 21392.50 18017.50 1.45 1.721

14 2448 2482 215.10 99.25 21348.68 17973.68 1.59 1.892

13 2447 2492 215.70 100.75 21731.78 18356.78 2.07 2.451

16 2442 2482 215.00 100.25 21553.75 18178.75 1.86 2.200

21 2452 2488 215.00 99.35 21360.25 17985.25 1.69 2.002

8 2436 2461 214.35 97.95 20995.58 17620.58 1.19 1.419

11 2444 2474 214.75 98.50 21152.88 17777.88 1.42 1.687

5 2458 2510 216.25 100.75 21787.19 18412.19 2.39 2.824

Sample 14 38 2467 2511 217.25 100.25 21779.31 18404.31 2.02 2.391

37 2444 2479 215.00 99.50 21392.50 18017.50 1.64 1.943

32 2466 2511 216.75 100.60 21805.05 18430.05 2.06 2.442

41 2437 2475 214.90 99.50 21382.55 18007.55 1.78 2.110

27 2454 2482 214.65 99.25 21304.01 17929.01 1.31 1.562

47 2452 2493 216.25 100.75 21787.19 18412.19 1.88 2.227

45 2455 2489 215.25 99.65 21449.66 18074.66 1.59 1.881

34 2465 2507 217.10 101.25 21981.38 18606.38 1.91 2.257

26 2454 2488 214.80 99.65 21404.82 18029.82 1.59 1.886

28 2468 2522 215.75 100.40 21661.30 18286.30 2.49 2.953

Sample 15

36 2463 2492 214.80 99.75 21426.30 18051.30 1.35 1.607

42 2524 2555 214.65 99.65 21389.87 18014.87 1.45 1.721

48 2478 2533 217.30 101.55 22066.82 18691.82 2.49 2.942

43 2428 2453 215.35 98.00 21104.30 17729.30 1.18 1.410

25 2469 2513 216.00 100.75 21762.00 18387.00 2.02 2.393

44 2493 2534 217.00 100.75 21862.75 18487.75 1.88 2.218

31 2448 2470 212.65 98.55 20956.66 17581.66 1.05 1.251

39 2480 2512 215.90 99.50 21482.05 18107.05 1.49 1.767

29 2458 2501 215.50 100.00 21550.00 18175.00 2.00 2.366

40 2458 2492 215.00 98.80 21242.00 17867.00 1.60 1.903

Sample 16

94 2476 2479 215.50 98.55 21237.53 17862.53 0.14 0.168

60 2488 2510 215.25 99.40 21395.85 18020.85 1.03 1.221

79 2456 2494 216.00 100.00 21600.00 18225.00 1.76 2.085

76 2482 2505 215.75 99.00 21359.25 17984.25 1.08 1.279

75 2443 2467 214.50 97.60 20935.20 17560.20 1.15 1.367

86 2463 2494 214.30 100.00 21430.00 18055.00 1.45 1.717

96 2467 2496 216.00 98.55 21286.80 17911.80 1.36 1.619

58 2479 2511 216.00 99.70 21535.20 18160.20 1.49 1.762

65 2450 2471 215.50 98.25 21172.88 17797.88 0.99 1.180

71 2444 2483 216.35 100.50 21743.18 18368.18 1.79 2.123

180

Sample 17 Brick

identification

Dry mass

(md) gm

Wet mass

(mw) gm

length (mm)

l

Width (mm)

b

Immersed area

(mm2) Agross

Immersed area

(mm2) Anet


kg/m2.min


kg/m2.min

51 2457 2501 216.25 100.95 21830.44 18455.44 2.02 2.384

88 2439 2465 215.50 99.00 21334.50 17959.50 1.22 1.448

83 2462 2495 215.45 100.50 21652.73 18277.73 1.52 1.805

53 2450 2480 214.50 99.80 21407.10 18032.10 1.40 1.664

57 2457 2488 215.30 100.25 21583.83 18208.83 1.44 1.702

92 2488 2519 214.95 100.00 21495.00 18120.00 1.44 1.711

56 2480 2503 215.00 99.10 21306.50 17931.50 1.08 1.283

72 2458 2489 214.55 100.25 21508.64 18133.64 1.44 1.710

55 2472 2493 214.25 99.25 21264.31 17889.31 0.99 1.174

74 2489 2504 214.55 98.90 21219.00 17844.00 0.71 0.841

Sample 18 49 2468 2492 214.10 100.25 21463.53 18088.53 1.12 1.327

91 2480 2512 216.85 100.45 21782.58 18407.58 1.47 1.738

89 2433 2457 213.70 98.45 21038.77 17663.77 1.14 1.359

61 2450 2471 216.00 98.30 21232.80 17857.80 0.99 1.176

80 2451 2491 216.00 100.50 21708.00 18333.00 1.84 2.182

95 2477 2499 215.25 98.00 21094.50 17719.50 1.04 1.242

82 2432 2474 216.40 100.25 21694.10 18319.10 1.94 2.293

77 2494 2530 215.80 99.50 21472.10 18097.10 1.68 1.989

54 2443 2468 213.95 99.15 21213.14 17838.14 1.18 1.401

84 2453 2490 215.00 100.25 21553.75 18178.75 1.72 2.035

Sample 19

93 2452 2492 215.35 99.75 21481.16 18106.16 1.86 2.209

66 2449 2489 215.50 100.55 21668.53 18293.53 1.85 2.187

59 2437 2474 215.20 99.70 21455.44 18080.44 1.72 2.046

73 2446 2481 215.50 100.25 21603.88 18228.88 1.62 1.920

68 2443 2484 216.20 100.45 21717.29 18342.29 1.89 2.235

50 2445 2484 215.25 100.00 21525.00 18150.00 1.81 2.149

64 2442 2468 214.15 99.00 21200.85 17825.85 1.23 1.459

90 2441 2476 214.50 99.50 21342.75 17967.75 1.64 1.948

52 2440 2472 214.65 99.90 21443.54 18068.54 1.49 1.771

81 2442 2465 213.75 97.90 20926.13 17551.13 1.10 1.310

Sample 20

11 2340 2385 216.00 100.00 21600.00 18225.00 2.08 2.469

32 2345 2357 214.60 97.25 20869.85 17494.85 0.57 0.686

18 2359 2382 215.00 98.75 21231.25 17856.25 1.08 1.288

31 2351 2393 216.25 99.75 21570.94 18195.94 1.95 2.308

7 2363 2401 216.10 99.35 21469.54 18094.54 1.77 2.100

2 2396 2431 217.25 100.60 21855.35 18480.35 1.60 1.894

6 2380 2422 212.80 100.25 21333.20 17958.20 1.97 2.339

38 2338 2352 214.00 97.55 20875.70 17500.70 0.67 0.800

17 2328 2352 214.00 97.55 20875.70 17500.70 1.15 1.371

29 2344 2384 215.85 99.65 21509.45 18134.45 1.86 2.206

181

Sample 21 Brick

identification

Dry mass

(md) gm

Wet mass

(mw) gm

length (mm)

l

Width (mm)

b

Immersed area

(mm2) Agross

Immersed area

(mm2) Anet


kg/m2.min


kg/m2.min

13 2355 2392 216.25 100.00 21625.00 18250.00 1.71 2.027

25 2307 2326 214.00 98.50 21079.00 17704.00 0.90 1.073

39 2326 2368 215.55 100.10 21576.56 18201.56 1.95 2.307

44 2374 2421 217.85 102.00 22220.70 18845.70 2.12 2.494

22 2358 2378 215.00 98.80 21242.00 17867.00 0.94 1.119

26 2377 2423 216.80 100.00 21680.00 18305.00 2.12 2.513

19 2358 2374 215.00 98.00 21070.00 17695.00 0.76 0.904

41 2371 2411 217.50 100.30 21815.25 18440.25 1.83 2.169

30 2236 2269 215.25 100.15 21557.29 18182.29 1.53 1.815

36 2400 2437 218.50 100.75 22013.88 18638.88 1.68 1.985

Sample 22 40 2347 2388 215.55 99.45 21436.45 18061.45 1.91 2.270

3 2358 2403 216.80 100.25 21734.20 18359.20 2.07 2.451

37 2300 2334 214.75 98.25 21099.19 17724.19 1.61 1.918

20 2334 2381 217.00 101.00 21917.00 18542.00 2.14 2.535

40 2400 2433 217.75 100.50 21883.88 18508.88 1.51 1.783

35 2383 2410 216.25 98.50 21300.63 17925.63 1.27 1.506

47 2363 2371 214.25 97.35 20857.24 17482.24 0.38 0.458

45 2336 2367 215.25 98.00 21094.50 17719.50 1.47 1.749

16 2361 2373 214.45 97.00 20801.65 17426.65 0.58 0.689

4 2328 2387 216.25 100.50 21733.13 18358.13 2.71 3.214

Sample 23

24 2334 2372 216.26 99.50 21517.87 18142.87 1.77 2.094

1 2357 2403 216.90 101.60 22037.04 18662.04 2.09 2.465

27 2341 2379 216.00 99.95 21589.20 18214.20 1.76 2.086

5 2352 2391 216.85 100.50 21793.43 18418.43 1.79 2.117

15 2482 2499 213.75 98.00 20947.50 17572.50 0.81 0.967

9 2325 2359 216.00 99.95 21589.20 18214.20 1.57 1.867

14 2366 2422 217.00 101.50 22025.50 18650.50 2.54 3.003

46 2344 2359 214.00 97.25 20811.50 17436.50 0.72 0.860

8 2354 2404 216.00 99.75 21546.00 18171.00 2.32 2.752

28 2304 2336 216.00 98.00 21168.00 17793.00 1.51 1.798

Sample 24

61 2373 2430 220.70 102.50 22621.75 19246.75 2.52 2.962

62 2359 2428 220.65 102.60 22638.69 19263.69 3.05 3.582

96 2393 2426 216.15 99.15 21431.27 18056.27 1.54 1.828

79 2384 2419 215.75 99.75 21521.06 18146.06 1.63 1.929

76 2310 2360 216.15 100.55 21733.88 18358.88 2.30 2.723

73 2338 2384 216.25 99.25 21462.81 18087.81 2.14 2.543

86 2308 2359 217.25 99.40 21594.65 18219.65 2.36 2.799

70 2356 2412 220.75 102.45 22615.84 19240.84 2.48 2.910

71 2351 2369 216.55 99.90 21633.35 18258.35 0.83 0.986

55 2298 2321 213.90 98.75 21122.63 17747.63 1.09 1.296

182

Sample 25 Brick

identification

Dry mass

(md) gm

Wet mass

(mw) gm

length (mm)

l

Width (mm)

b

Immersed area

(mm2) Agross

Immersed area

(mm2) Anet


kg/m2.min


kg/m2.min

78 2313 2362 216.30 100.25 21684.08 18309.08 2.26 2.676

53 2363 2380 215.00 98.75 21231.25 17856.25 0.80 0.952

80 2379 2427 217.25 101.25 21996.56 18621.56 2.18 2.578

89 2330 2384 217.05 100.50 21813.53 18438.53 2.48 2.929

88 2313 2360 216.25 100.50 21733.13 18358.13 2.16 2.560

77 2288 2319 215.50 99.50 21442.25 18067.25 1.45 1.716

94 2316 2365 215.90 99.75 21536.03 18161.03 2.28 2.698

85 2332 2370 217.30 99.35 21588.76 18213.76 1.76 2.086

74 2377 2392 217.00 99.50 21591.50 18216.50 0.69 0.823

82 2353 2402 216.85 100.25 21739.21 18364.21 2.25 2.668

Sample 26 52 2321 2347 215.25 98.25 21148.31 17773.31 1.23 1.463

50 2342 2346 214.55 98.75 21186.81 17811.81 0.19 0.225

64 2398 2411 216.50 99.15 21465.98 18090.98 0.61 0.719

84 2299 2347 217.75 100.00 21775.00 18400.00 2.20 2.609

56 2357 2375 215.75 99.75 21521.06 18146.06 0.84 0.992

93 2318 2368 216.90 100.10 21711.69 18336.69 2.30 2.727

67 2351 2407 220.50 102.00 22491.00 19116.00 2.49 2.929

90 2361 2380 215.75 97.85 21111.14 17736.14 0.90 1.071

91 2329 2380 215.85 100.30 21649.76 18274.76 2.36 2.791

59 2302 2321 216.90 99.65 21614.09 18239.09 0.88 1.042

Sample 27

57 2393 2416 217.50 100.45 21847.88 18472.88 1.05 1.245

81 2323 2372 216.30 100.25 21684.08 18309.08 2.26 2.676

69 2365 2384 216.00 99.25 21438.00 18063.00 0.89 1.052

66 2387 2392 215.65 99.10 21370.92 17995.92 0.23 0.278

68 2399 2418 216.25 99.40 21495.25 18120.25 0.88 1.049

79 2363 2403 216.60 99.25 21497.55 18122.55 1.86 2.207

65 2312 2339 214.00 98.00 20972.00 17597.00 1.29 1.534

58 2377 2399 217.00 99.90 21678.30 18303.30 1.01 1.202

54 2346 2370 216.95 100.00 21695.00 18320.00 1.11 1.310

63 2301 2348 215.00 99.35 21360.25 17985.25 2.20 2.613

A 4


WATER ABSORPTION OF BRICKS

184

Sample 1 Sample 2

Brick Dry mass Saturated mass

A (Water absorption)%

identification W1(gm) W2 (gm)

A= 100( W2-W1)/W1

2 2390 2590 8.37 9 2435 2760 13.35

11 2415 2665 10.35 3 2435 2650 8.83

15 2465 2700 9.53 17 2430 2720 11.93 12 2420 2675 10.54 18 2430 2625 8.02 6 2410 2690 11.62

16 2445 2740 12.07 Sample 4

82 2505 2795 11.58 95 2280 2567 12.59 85 2306 2553 10.71 84 2306 2555 10.80 92 2299 2565 11.57 98 2403 2692 12.03 81 2447 2712 10.83 100 2399 2669 11.25 89 2288 2594 13.37 42 2420 2676 10.58

Sample 6

19 2450 2715 10.82 71 2295 2596 13.12 79 2449 2752 12.37 72 2300 2586 12.43 61 2540 2816 10.87 60 2446 2727 11.49 15 2410 2652 10.04 62 2448 2740 11.93 78 2415 2687 11.26 75 2376 2642 11.20

Sample 8

9 2483 2790 12.36 55 2412 2662 10.36 4 2430 2676 10.12

10 2304 2589 12.37 14 2456 2740 11.56 56 2328 2576 10.65 12 2493 2792 11.99 48 2506 2795 11.53 5 2497 2803 12.25

54 2412 2664 10.45



identification W1(gm) W2 (gm) A= 100( W2-W1)/W1

7 2415 2670 10.559 5 2460 2710 10.163 1 2380 2640 10.924 13 2370 2670 12.658 8 2410 2640 9.544 14 2370 2645 11.603 4 2370 2625 10.759 20 2410 2665 10.581 19 2440 2775 13.730 10 2485 2745 10.463

Sample 3 39 2440 2695 10.45 69 2420 2685 10.95 35 2410 2680 11.20 41 2415 2695 11.59 37 2400 2655 10.63 29 2410 2685 11.41 40 2410 2670 10.79 68 2430 2745 12.96 63 2435 2735 12.32 71 2440 2710 11.07

Sample 5 99 2400 2684 11.83 86 2281 2576 12.93 97 2472 2774 12.22 43 2378 2706 13.79 91 2265 2517 11.13 90 2318 2559 10.40 96 2500 2810 12.40 87 2414 2684 11.18 41 2364 2658 12.44 88 2292 2542 10.91

Sample 7 11 2386 2673 12.03 77 2401 2676 11.45 16 2425 2688 10.85 76 2439 2722 11.60 20 2444 2731 11.74 17 2434 2734 12.33 74 2407 2701 12.21 80 2466 2786 12.98 73 2263 2556 12.95 51 2296 2570 11.93

185

Sample 9 Sample 10 Brick Dry mass Saturated

mass A (Water absorption)%


A= 100( W2-W1)/W1

22 2464 2760 12.01 58 2489 2747 10.37 37 2304 2572 11.63 66 2422 2665 10.03 67 2307 2577 11.70 26 2322 2619 12.79 59 2450 2702 10.29 45 2382 2606 9.40 28 2518 2824 12.15 68 2384 2707 13.55

Sample 12

13 2447 2738 11.89 9 2452 2729 11.30 12 2449 2744 12.05 20 2449 2760 12.70 3 2449 2706 10.49 7 2452 2710 10.52 19 2409 2659 10.38 24 2449 2761 12.74 11 2444 2699 10.43 10 2436 2711 11.29

Sample 14

34 2465 2770 12.37 41 2437 2709 11.16 32 2466 2767 12.21 27 2454 2713 10.55 38 2467 2766 12.12 48 2478 2796 12.83 45 2455 2728 11.12 40 2458 2720 10.66 29 2458 2736 11.31 37 2444 2713 11.01

Sample 16

75 2482 2672 7.66 86 2463 2717 10.31 91 2480 2761 11.33 71 2444 2738 12.03 65 2450 2687 9.67 79 2456 2735 11.36 80 2451 2734 11.55 96 2467 2721 10.30 83 2462 2729 10.84 58 2479 2723 9.84




49 2464 2757 11.89 46 2489 2805 12.70 2 2304 2562 11.20 1 2435 2670 9.65 52 2370 2644 11.56 7 2420 2709 11.94 57 2483 2759 11.12 3 2502 2821 12.75 50 2358 2668 13.15 6 2372 2657 12.02

Sample 11 29 2503 2832 13.14 21 2411 2687 11.45 31 2502 2819 12.67 34 2495 2797 12.10 94 2240 2487 11.03 30 2458 2759 12.25 33 2445 2742 12.15 69 2496 2774 11.14 35 2398 2680 11.76 32 2543 2836 11.52

Sample 13 22 2443 2684 9.86 8 2436 2654 8.95 21 2452 2722 11.01 15 2448 2727 11.40 23 2456 2745 11.77 17 2459 2710 10.21 16 2442 2724 11.55 18 2443 2735 11.95 5 2458 2759 12.25 14 2448 2712 10.78

Sample 15 47 2452 2743 11.87 44 2493 2783 11.63 42 2524 2789 10.50 43 2428 2678 10.30 36 2463 2736 11.08 25 2469 2760 11.79 31 2448 2672 9.15 26 2454 2720 10.84 28 2468 2757 11.71 39 2480 2728 10.00

186




A= 100( W2-W1)/W1

88 2439 2692 10.37 93 2452 2703 10.24 84 2453 2724 11.05 92 2488 2744 10.29 66 2449 2731 11.51 68 2443 2734 11.91 73 2446 2725 11.41 59 2437 2715 11.41 81 2442 2673 9.46 53 2450 2709 10.57

Sample 20

19 2358 2560 8.57 44 2374 2697 13.61 30 2236 2496 11.63 41 2371 2665 12.40 36 2400 2665 11.04 7 2363 2634 11.47 38 2338 2536 8.47 2 2396 2675 11.64 25 2307 2537 9.97 29 2344 2618 11.69

Sample 22

69 2365 2609 10.32 66 2387 2617 9.64 58 2377 2649 11.44 63 2301 2556 11.08 79 2363 2614 10.62 61 2373 2705 13.99 70 2356 2670 13.33 71 2351 2612 11.10 65 2312 2540 9.86 96 2393 2633 10.03

Sample 24

57 2393 2687 12.29 56 2357 2615 10.95 93 2318 2620 13.03 85 2332 2626 12.61 84 2299 2609 13.48 94 2316 2604 12.44 82 2353 2653 12.75 67 2351 2689 14.38 54 2346 2630 12.11 74 2377 2660 11.91




74 2489 2709 8.84 61 2450 2675 9.18 76 2482 2712 9.27 60 2488 2707 8.80 49 2468 2718 10.13 55 2472 2709 9.59 95 2477 2706 9.25 89 2433 2655 9.12 94 2476 2711 9.49 72 2458 2713 10.37

Sample 19 57 2457 2731 11.15 52 2440 2704 10.82 51 2457 2754 12.09 56 2480 2712 9.35 77 2494 2740 9.86 54 2443 2690 10.11 64 2442 2692 10.24 90 2441 2696 10.45 82 2432 2728 12.17 50 2445 2724 11.41

Sample 21 6 2380 2680 12.61 18 2374 2579 8.64 13 2355 2641 12.14 31 2351 2627 11.74 22 2358 2586 9.67 11 2341 2624 12.09 26 2377 2663 12.03 32 2345 2547 8.61 39 2326 2600 11.78 17 2328 2520 8.25

Sample 23 55 2298 2512 9.31 78 2313 2617 13.14 73 2338 2618 11.98 79 2384 2631 10.36 86 2308 2602 12.74 76 2310 2609 12.94 53 2363 2583 9.31 81 2323 2619 12.74 62 2308 2620 13.52 68 2399 2671 11.34

187




A= 100( W2-W1)/W1

20 2334 2607 11.70 35 2383 2572 7.93 15 2482 2566 9.34 45 2336 2571 10.06 37 2300 2673 11.65 1 2357 2642 12.09 14 2366 2569 8.58 27 2341 2557 9.23 47 2363 2624 11.05 3 2358 2665 13.02




88 2313 2607 12.71 90 2361 2572 8.94 50 2342 2566 9.56 59 2302 2571 11.69 80 2379 2673 12.36 89 2330 2642 13.39 52 2321 2569 10.69 77 2288 2557 11.76 91 2329 2624 12.67 64 2398 2665 11.13

Sample 27 5 2352 2647 12.54 9 2325 2608 12.17 24 2334 2614 12.00 16 2361 2548 7.92 4 2328 2623 12.67 8 2354 2646 12.40 40 2400 2672 11.33 46 2344 2551 8.83 28 2304 2568 11.46 41 2347 2623 11.76

A 5


COMPRESSIVE STRENGTH OF BRICKS

189

FACING BRICK – BED FACE Sample 1 Dimension 1 (mm) Dimension 2 (mm) Brick

Identification Length Width

Area 1 mm2 Length Width

Area 2 mm2

Smaller area mm2

Max load Kn


18 216.10 98.50 21285.85 216.20 98.50 21295.70 21285.85 894.10 42.00

12 212.85 100.00 21285.00 217.85 99.90 21763.22 21285.00 988.80 46.46

14 217.75 99.35 21633.46 217.90 99.65 21713.74 21633.46 944.90 43.68

10 218.95 99.95 21884.05 218.75 99.65 21798.44 21798.44 1036.90 47.57

17 219.50 100.55 22070.73 219.40 100.75 22104.55 22070.73 840.90 38.10

11 217.25 99.40 21594.65 217.10 99.85 21677.44 21594.65 820.90 38.01

16 219.50 100.25 22004.88 220.10 100.20 22054.02 22004.88 776.90 35.31

6 217.20 99.80 21676.56 217.45 99.65 21668.89 21668.89 913.90 42.18

2 215.20 97.60 21003.52 215.55 98.20 21167.01 21003.52 694.90 33.08

8 216.60 98.70 21378.42 216.30 98.65 21338.00 21338.00 844.90 39.60

Sample 2

71 217.05 100.50 21813.53 218.15 100.75 21978.61 21813.53 1064.30 48.79

63 219.25 101.00 22144.25 219.50 101.10 22191.45 22144.25 957.30 43.23

39 217.30 99.50 21621.35 217.35 99.45 21615.46 21615.46 964.30 44.61

68 219.90 101.45 22308.86 220.50 101.35 22347.68 22308.86 977.00 43.79

69 217.50 99.85 21717.38 217.05 100.05 21715.85 21715.85 1091.90 50.28

35 217.55 99.10 21559.21 217.70 99.00 21552.30 21552.30 1106.00 51.32

40 216.95 99.25 21532.29 217.00 99.15 21515.55 21515.55 1113.00 51.73

41 217.50 99.55 21652.13 217.10 99.50 21601.45 21601.45 1187.00 54.95

29 217.00 100.00 21700.00 217.20 99.85 21687.42 21687.42 965.00 44.50

37 217.00 99.40 21569.80 216.45 99.25 21482.66 21482.66 1159.90 53.99

Sample 3

96 220.85 102.25 22581.91 221.25 102.25 22622.81 22581.91 803.40 35.58

91 214.00 97.95 20961.30 214.00 97.65 20897.10 20897.10 874.10 41.83

90 214.25 98.35 21071.49 214.20 98.40 21077.28 21071.49 942.30 44.72

43 219.20 101.95 22347.44 219.20 101.80 22314.56 22314.56 797.90 35.76

41 218.20 101.30 22103.66 218.00 101.30 22083.40 22083.40 684.80 31.01

88 214.35 97.95 20995.58 214.40 97.15 20828.96 20828.96 947.80 45.50

87 217.20 100.45 21817.74 217.75 100.25 21829.44 21817.74 885.90 40.60

82 219.90 101.70 22363.83 220.20 101.50 22350.30 22350.30 793.90 35.52

42 217.45 100.15 21777.62 217.00 100.10 21721.70 21721.70 930.90 42.86

89 215.95 99.75 21541.01 215.50 99.65 21474.58 21474.58 776.90 36.18

Sample 4

51 216.00 98.60 21297.60 216.10 98.80 21350.68 21297.60 777.90 36.53

80 219.50 101.10 22191.45 219.55 101.45 22273.35 22191.45 912.90 41.14

15 215.25 98.75 21255.94 214.30 98.50 21108.55 21108.55 1020.90 48.36

62 218.60 101.75 22242.55 219.40 101.88 22352.47 22242.55 855.80 38.48

78 218.20 101.70 22190.94 218.65 101.20 22127.38 22127.38 676.70 30.58

11 215.35 97.66 21031.08 214.50 97.59 20933.06 20933.06 614.70 29.37

73 217.80 101.35 22074.03 217.35 100.15 21767.60 21767.60 589.60 27.09

20 219.00 101.85 22305.15 220.01 101.45 22320.01 22305.15 853.70 38.27

75 217.95 100.65 21936.67 217.14 100.55 21833.43 21833.43 777.60 35.62

72 215.55 99.95 21544.22 215.75 99.95 21564.21 21544.22 639.60 29.69

190

Sample 5 Dimension 1 (mm) Dimension 2 (mm) Brick


Area 1 mm2

Length Width

Area 2 mm2

Smaller area mm2

Max load Kn


4 216.85 98.95 21457.31 216.10 98.80 21350.68 21350.68 1203.00 56.34

3 221.30 102.65 22716.45 221.00 102.40 22630.40 22630.40 928.00 41.01

57 217.70 101.75 22150.98 217.80 101.65 22139.37 22139.37 1276.90 57.68

48 221.20 101.45 22440.74 221.30 101.50 22461.95 22440.74 938.00 41.80

12 220.55 101.35 22352.74 220.30 101.40 22338.42 22338.42 761.90 34.11

55 215.30 100.00 21530.00 215.25 99.98 21520.70 21520.70 1000.90 46.51

6 217.25 99.50 21616.38 217.35 99.54 21635.02 21616.38 1123.80 51.99

7 217.20 99.65 21643.98 217.30 99.55 21632.22 21632.22 1275.80 58.98

10 219.45 100.95 22153.48 219.40 100.55 22060.67 22060.67 882.70 40.01

9 219.50 101.35 22246.33 219.35 101.50 22264.03 22246.33 935.80 42.07

Sample 6

32 220.00 102.95 22649.00 221.00 103.75 22928.75 22649.00 903.90 39.91

31 220.65 102.25 22561.46 220.60 102.10 22523.26 22523.26 879.00 39.03

69 219.35 101.15 22187.25 219.10 101.30 22194.83 22187.25 1015.90 45.79

35 217.70 100.00 21770.00 217.70 99.90 21748.23 21748.23 1055.90 48.55

34 220.25 101.75 22410.44 219.85 101.75 22369.74 22369.74 904.00 40.41

33 219.25 100.95 22133.29 219.30 101.25 22204.13 22133.29 958.00 43.28

29 221.25 102.50 22678.13 221.00 102.75 22707.75 22678.13 877.90 38.71

21 220.00 99.25 21835.00 219.85 99.30 21831.11 21831.11 1066.00 48.83

94 210.00 98.35 20653.50 209.80 98.70 20707.26 20653.50 1126.90 54.56

68 218.65 98.70 21580.76 218.45 98.50 21517.33 21517.33 1238.90 57.58

Sample 7

21 215.50 99.35 21409.93 215.50 99.55 21453.03 21409.93 1322.10 61.75

18 215.60 100.45 21657.02 215.75 100.50 21682.88 21657.02 1280.10 59.11

13 215.75 100.75 21736.81 215.95 100.75 21756.96 21736.81 1190.10 54.75

8 214.00 98.75 21132.50 214.00 97.50 20865.00 20865.00 1512.10 72.47

15 215.75 100.00 21575.00 215.25 100.00 21525.00 21525.00 1292.10 60.03

23 215.75 100.50 21682.88 216.00 100.50 21708.00 21682.88 1291.10 59.54

22 213.65 99.25 21204.76 213.75 99.15 21193.31 21193.31 1348.10 63.61

17 215.00 99.00 21285.00 215.00 98.75 21231.25 21231.25 1404.10 66.13

10 215.25 100.00 21525.00 215.40 100.25 21593.85 21525.00 1007.10 46.79

5 216.50 100.70 21801.55 216.25 100.75 21787.19 21787.19 967.10 44.39

Sample 8

44 217.00 100.85 21884.45 216.95 100.75 21857.71 21857.71 993.70 45.46

47 215.95 100.75 21756.96 216.25 100.75 21787.19 21756.96 1112.70 51.14

28 215.85 100.25 21638.96 215.80 100.25 21633.95 21633.95 1087.70 50.28

29 215.50 100.25 21603.88 215.45 100.35 21620.41 21603.88 1077.80 49.89

26 215.25 99.75 21471.19 214.75 99.80 21432.05 21432.05 617.80 28.83

37 215.00 99.40 21371.00 215.10 99.50 21402.45 21371.00 1183.80 55.39

39 215.75 99.25 21413.19 214.95 99.45 21376.78 21376.78 1208.80 56.55

40 214.85 98.90 21248.67 215.00 98.80 21242.00 21242.00 1127.80 53.09

31 213.00 98.75 21033.75 213.00 98.55 20991.15 20991.15 1435.30 68.38

45 215.25 99.75 21471.19 215.25 99.90 21503.48 21471.19 1142.30 53.20

191

Sample 9

Dimension 1 (mm) Dimension 2 (mm) Brick Identific

ation Length Width

Area 1 mm2

Length Width

Area 2 mm2

Smaller area mm2

Max load Kn


43 215.45 98.00 21114.10 215.50 97.90 21097.45 21097.45 1128.30 53.48

38 217.30 100.25 21784.33 216.75 100.35 21750.86 21750.86 916.20 42.12

25 216.25 101.00 21841.25 216.25 100.65 21765.56 21765.56 1169.80 53.75

48 217.35 101.30 22017.56 217.45 101.60 22092.92 22017.56 1066.80 48.45

42 214.30 99.75 21376.43 214.50 99.75 21396.38 21376.43 1020.30 47.73

32 216.75 100.50 21783.38 216.75 100.50 21783.38 21783.38 1098.30 50.42

36 216.70 99.85 21637.50 215.00 99.85 21467.75 21467.75 1089.30 50.74

27 214.90 99.40 21361.06 214.75 99.35 21335.41 21335.41 1161.90 54.46

41 214.95 99.55 21398.27 214.90 99.65 21414.79 21398.27 1299.80 60.74

34 217.30 101.50 22055.95 217.25 101.35 22018.29 22018.29 1049.80 47.68

Sample 10

50 215.25 99.80 21481.95 215.35 99.75 21481.16 21481.16 1035.60 48.21

54 214.00 99.00 21186.00 213.95 99.20 21223.84 21186.00 1105.60 52.19

77 215.95 99.60 21508.62 215.90 99.75 21536.03 21508.62 1126.60 52.38

82 216.50 100.40 21736.60 216.65 100.25 21719.16 21719.16 881.60 40.59

64 214.15 99.25 21254.39 214.25 99.10 21232.18 21232.18 1177.50 55.46

56 215.25 99.00 21309.75 215.00 99.15 21317.25 21309.75 1139.50 53.47

51 216.45 100.75 21807.34 215.25 101.00 21740.25 21740.25 1091.50 50.21

52 215.00 99.80 21457.00 214.75 99.85 21442.79 21442.79 1007.50 46.99

57 215.65 100.25 21618.91 215.45 100.15 21577.32 21577.32 1077.50 49.94

59 215.25 99.75 21471.19 215.15 99.70 21450.46 21450.46 1043.50 48.65

Sample 11

39 215.50 100.00 21550.00 215.45 100.00 21545.00 21545.00 977.00 45.35

13 216.15 99.80 21571.77 216.00 100.40 21686.40 21571.77 931.00 43.16

31 216.45 99.95 21634.18 216.25 100.00 21625.00 21625.00 922.00 42.64

18 215.00 98.85 21252.75 215.35 98.30 21168.91 21168.91 1132.00 53.47

6 217.90 100.25 21844.48 218.25 100.50 21934.13 21844.48 838.00 38.36

17 214.00 97.50 20865.00 214.25 97.50 20889.38 20865.00 842.00 40.35

29 215.75 99.75 21521.06 215.75 99.75 21521.06 21521.06 886.00 41.17

25 214.65 98.25 21089.36 214.00 98.25 21025.50 21025.50 1025.00 48.75

32 215.35 97.75 21050.46 214.40 97.70 20946.88 20946.88 928.00 44.30

26 216.90 100.00 21690.00 216.75 100.20 21718.35 21690.00 945.00 43.57

Sample 12

69 216.10 99.15 21426.32 216.25 99.15 21441.19 21426.32 1109.00 51.76

62 221.00 102.60 22674.60 220.75 102.75 22682.06 22674.60 797.00 35.15

65 214.25 98.00 20996.50 214.25 97.50 20889.38 20889.38 998.00 47.78

76 216.30 100.50 21738.15 216.25 100.50 21733.13 21733.13 869.00 39.99

86 217.55 99.30 21602.72 217.50 99.40 21619.50 21602.72 904.00 41.85

96 216.35 99.75 21580.91 216.00 99.25 21438.00 21438.00 971.00 45.29

81 216.35 99.75 21580.91 216.45 99.75 21590.89 21580.91 914.00 42.35

71 216.50 99.85 21617.53 216.45 99.40 21515.13 21515.13 1270.00 59.03

70 220.75 102.45 22615.84 220.75 102.50 22626.88 22615.84 769.00 34.00

61 220.50 102.45 22590.23 220.80 102.50 22632.00 22590.23 815.00 36.08

192

Sample 13 Dimension 1 (mm) Dimension 2 (mm) Brick


Area 1 mm2

Length Width

Area 2 mm2

Smaller area mm2

Max load Kn


64 216.50 99.15 21465.98 216.25 99.10 21430.38 21430.38 1374.00 64.11

74 217.20 99.40 21589.68 217.00 99.50 21591.50 21589.68 1056.00 48.91

88 216.35 100.45 21732.36 216.35 100.55 21753.99 21732.36 889.00 40.91

90 215.25 97.80 21051.45 215.65 97.50 21025.88 21025.88 1216.00 57.83

54 216.75 100.00 21675.00 216.75 100.05 21685.84 21675.00 1109.00 51.16

84 217.70 100.25 21824.43 218.05 99.90 21783.20 21783.20 838.00 38.47

67 220.60 102.30 22567.38 220.55 102.00 22496.10 22496.10 881.00 39.16

85 217.35 99.50 21626.33 217.75 99.50 21666.13 21626.33 924.00 42.73

82 216.70 100.10 21691.67 216.95 100.00 21695.00 21691.67 856.00 39.46

77 215.25 99.75 21471.19 215.30 99.75 21476.18 21471.19 790.00 36.79

Sample 14

40 215.75 99.25 21413.19 216.10 99.30 21458.73 21413.19 844.00 39.41

46 214.35 97.75 20952.71 214.00 97.40 20843.60 20843.60 865.00 41.50

28 215.95 93.00 20083.35 216.00 98.00 21168.00 20083.35 1007.00 50.14

5 217.10 100.25 21764.28 217.00 100.45 21797.65 21764.28 905.00 41.58

4 216.30 100.70 21781.41 216.25 100.55 21743.94 21743.94 866.00 39.83

3 216.70 100.00 21670.00 216.50 100.00 21650.00 21650.00 891.00 41.15

16 215.00 97.00 20855.00 214.65 97.00 20821.05 20821.05 1179.00 56.63

47 214.25 97.45 20878.66 214.15 97.35 20847.50 20847.50 1013.00 48.59

27 215.90 99.70 21525.23 216.25 99.75 21570.94 21525.23 936.00 43.48

14 217.10 101.10 21948.81 217.00 101.30 21982.10 21948.81 892.00 40.64

FACING BRICK – STRETCHER FACE Sample 1

27 218.00 67.50 14715.00 214.90 67.45 14495.01 14495.01 570.00 39.32

38 217.00 67.30 14604.10 216.50 66.75 14451.38 14451.38 569.00 39.37

30 217.55 64.50 14031.98 217.30 64.50 14015.85 14015.85 488.00 34.82

3 217.25 67.75 14718.69 217.00 68.00 14756.00 14718.69 573.00 38.93

60 217.10 68.35 14838.79 217.15 68.00 14766.20 14766.20 581.00 39.35

43 217.95 66.90 14580.86 217.50 67.00 14572.50 14572.50 540.00 37.06

66 216.85 67.30 14594.01 216.85 68.00 14745.80 14594.01 538.00 36.86

25 218.00 67.10 14627.80 217.65 66.00 14364.90 14364.90 529.00 36.83

23 216.50 67.90 14700.35 216.50 68.00 14722.00 14700.35 544.00 37.01

44 217.70 67.75 14749.18 217.00 67.75 14701.75 14701.75 490.00 33.33

Sample 2

74 217.00 68.80 14929.60 217.55 70.00 15228.50 14929.60 504.90 33.82

76 217.25 68.75 14935.94 217.00 68.00 14756.00 14756.00 394.80 26.76

77 217.30 68.75 14939.38 217.25 68.70 14925.08 14925.08 499.80 33.49

61 217.80 69.25 15082.65 217.95 69.50 15147.53 15082.65 491.80 32.61

79 220.65 67.20 14827.68 220.75 67.50 14900.63 14827.68 427.90 28.86

97 218.30 68.80 15019.04 218.55 70.00 15298.50 15019.04 569.90 37.95

92 214.85 68.00 14609.80 214.25 67.75 14515.44 14515.44 455.90 31.41

100 217.10 67.85 14730.24 217.25 67.70 14707.83 14707.83 410.00 27.88

98 218.50 68.00 14858.00 218.95 67.50 14779.13 14779.13 456.00 30.85

95 219.75 68.60 15074.85 219.75 68.20 14986.95 14986.95 404.00 26.96

193

FACING BRICK – STRETCHER FACE Sample 3 Dimension 1 (mm) Dimension 2 (mm) Brick


Area 1 mm2

Length Width

Area 2 mm2

Smaller area mm2

Max load Kn


37 214.50 68.55 14703.98 214.25 68.00 14569.00 14569.00 513.90 35.27

66 214.30 66.20 14186.66 214.25 66.80 14311.90 14186.66 535.00 37.71

59 216.00 68.00 14688.00 216.00 67.55 14590.80 14590.80 634.00 43.45

30 218.25 69.50 15168.38 217.75 69.65 15166.29 15166.29 516.00 34.02

28 220.55 69.00 15217.95 220.75 68.25 15066.19 14482.86 497.80 34.37

52 217.00 66.85 14506.45 217.15 66.55 14451.33 14451.33 429.80 29.74

46 220.65 68.05 15015.23 220.45 68.00 14990.60 14990.60 336.60 22.45

5 219.25 69.25 15183.06 219.35 69.30 15200.96 15183.06 522.80 34.43

1 216.50 66.95 14494.68 216.55 66.88 14482.86 14482.86 506.80 34.99

4 214.25 66.35 14215.49 214.20 66.40 14222.88 14215.49 503.80 35.44

Sample 4

9 215.00 67.20 14448.00 215.00 67.00 14405.00 14405.00 495.10 34.37

16 215.10 67.20 14454.72 214.75 67.00 14388.25 14388.25 514.10 35.73

12 216.00 67.25 14526.00 215.70 66.95 14441.12 14441.12 479.10 33.18

14 215.00 67.25 14458.75 214.75 66.70 14323.83 14323.83 576.20 40.23

11 215.00 67.35 14480.25 214.40 67.00 14364.80 14364.80 496.20 34.54

37 214.50 68.55 14703.98 214.25 68.00 14569.00 14569.00 513.90 35.27

66 214.30 66.20 14186.66 214.25 66.80 14311.90 14186.66 535.00 37.71

59 216.00 68.00 14688.00 216.00 67.55 14590.80 14590.80 634.00 43.45

30 218.25 69.50 15168.38 217.75 69.65 15166.29 15166.29 516.00 34.02

28 220.55 69.00 15217.95 220.75 68.25 15066.19 14482.86 397.80 27.47

Sample 5

49 213.90 67.00 14331.30 214.00 62.75 13428.50 13428.50 549.60 40.93

60 215.25 67.00 14421.75 215.00 66.20 14233.00 14233.00 704.60 49.50

55 214.00 67.00 14338.00 213.80 67.00 14324.60 14324.60 639.50 44.64

76 215.25 66.75 14367.94 215.40 66.85 14399.49 14367.94 651.50 45.34

72 214.00 67.00 14338.00 214.15 67.00 14348.05 14338.00 557.50 38.88

95 214.75 67.00 14388.25 215.00 67.50 14512.50 14388.25 644.50 44.79

58 215.75 67.00 14455.25 215.90 67.25 14519.28 14455.25 635.50 43.96

94 215.25 67.00 14421.75 215.25 67.00 14421.75 14421.75 513.50 35.61

89 213.25 66.00 14074.50 213.25 66.25 14127.81 14074.50 774.50 55.03

61 215.25 67.00 14421.75 214.85 67.00 14394.95 14394.95 618.50 42.97

Sample 6

90 213.85 67.00 14327.95 214.00 66.75 14284.50 14284.50 541.50 37.91

68 216.00 67.45 14569.20 215.75 67.70 14606.28 14569.20 412.50 28.31

73 215.15 67.25 14468.84 215.35 67.45 14525.36 14468.84 487.50 33.69

92 214.55 67.75 14535.76 214.85 67.55 14513.12 14513.12 551.50 38.00

53 214.50 66.90 14350.05 214.25 66.85 14322.61 14322.61 487.50 34.04

81 213.95 66.50 14227.68 214.00 66.90 14316.60 14227.68 680.50 47.83

84 215.00 67.00 14405.00 215.30 67.30 14489.69 14405.00 539.50 37.45

93 215.25 66.75 14367.94 214.90 66.25 14237.13 14237.13 539.50 37.89

66 215.20 67.00 14418.40 215.25 67.45 14518.61 14418.40 506.50 35.13

88 215.40 66.90 14410.26 215.25 67.00 14421.75 14421.75 531.50 36.85

194

FACING BRICK – STRETCHER FACE Sample 7 Dimension 1 (mm) Dimension 2 (mm) Brick


Area 1 mm2

Length Width

Area 2 mm2

Smaller area mm2

Max load Kn


11 215.55 67.50 14549.63 215.50 67.65 14578.58 14549.63 323.00 22.20

2 217.00 67.75 14701.75 217.25 68.00 14773.00 14701.75 460.00 31.29

22 215.00 67.00 14405.00 214.85 66.75 14341.24 14341.24 653.00 45.53

19 214.70 67.20 14427.84 214.55 66.75 14321.21 14321.21 541.00 37.78

44 217.95 68.25 14875.09 217.55 68.25 14847.79 14847.79 285.00 19.19

30 214.85 63.10 13557.04 214.90 65.75 14129.68 13557.04 407.00 30.02

41 217.40 67.85 14750.59 217.45 67.75 14732.24 14732.24 481.00 32.65

38 214.00 66.35 14198.90 214.55 66.75 14321.21 14198.90 227.00 15.99

36 218.50 69.00 15076.50 217.80 68.00 14810.40 14810.40 411.00 27.75

7 216.00 67.80 14644.80 216.10 67.95 14684.00 14644.80 351.00 23.97

Sample 8

93 216.50 67.70 14657.05 216.50 67.45 14602.93 14602.93 422.00 28.90

89 217.30 67.80 14732.94 217.65 67.75 14745.79 14732.94 350.00 23.76

56 215.75 66.75 14401.31 215.45 66.75 14381.29 14381.29 381.00 26.49

57 217.20 68.90 14965.08 217.25 68.80 14946.80 14946.80 382.00 25.56

80 217.00 67.95 14745.15 217.35 68.55 14899.34 14745.15 373.00 25.30

94 216.25 67.45 14586.06 216.25 67.50 14596.88 14586.06 407.00 27.90

91 215.55 67.25 14495.74 215.95 68.00 14684.60 14495.74 430.00 29.66

52 214.95 67.00 14401.65 215.25 66.55 14324.89 14324.89 443.00 30.93

59 216.55 65.00 14075.75 216.65 66.25 14353.06 14075.75 435.00 30.90

50 214.35 66.00 14147.10 214.00 66.25 14177.50 14147.10 486.00 34.35

FACING BRICK – HEADER FACE Sample 1

70 98.50 67.30 6629.05 98.75 66.95 6611.31 6611.31 62.60 9.47

62 100.35 67.75 6798.71 99.50 67.00 6666.50 6666.50 62.20 9.33

45 67.25 100.10 6731.73 100.50 67.30 6763.65 6731.73 60.30 8.96

1 99.15 66.75 6618.26 100.25 67.25 6741.81 6618.26 60.80 9.19

16 99.55 66.85 6654.92 99.25 67.50 6699.38 6654.92 53.00 7.96

36 100.00 67.05 6705.00 100.95 67.00 6763.65 6705.00 56.30 8.40

64 100.65 67.30 6773.75 99.75 67.45 6728.14 6728.14 53.30 7.92

24 100.31 66.80 6700.71 100.20 66.50 6663.30 6679.68 61.20 9.16

5 99.80 66.65 6651.67 99.50 66.45 6611.78 6611.78 57.90 8.76

19 100.00 66.95 6695.00 99.95 67.10 6706.65 6695.00 61.00 9.11

Sample 2

17 101.10 68.95 6970.85 101.55 68.42 6948.05 6948.05 18.50 2.66

60 99.65 68.05 6781.18 99.91 68.00 6793.88 6781.18 27.00 3.98

16 100.85 67.25 6782.16 100.65 67.00 6743.55 6743.55 23.60 3.50

19 100.10 67.85 6791.79 100.15 67.77 6787.17 6787.17 26.70 3.93

71 100.00 68.75 6875.00 99.95 68.30 6826.59 6826.59 15.60 2.29

84 98.55 67.95 6696.47 97.25 67.55 6569.24 6569.24 29.70 4.52

81 100.15 67.30 6740.10 100.25 67.85 6801.96 6740.10 24.30 3.61

99 100.10 68.20 6826.82 99.85 68.25 6814.76 6814.76 20.80 3.05

85 96.45 67.70 6529.67 98.55 68.05 6706.33 6529.67 27.90 4.27

86 98.60 67.95 6699.87 99.00 68.30 6761.70 6699.87 28.40 4.24

195

FACING BRICK – HEADER FACE Sample 3 Dimension 1 (mm) Area 1

mm2 Dimension 2 (mm) Brick

Identification

Length Width Length Width

Area 2 mm2

Smaller area mm2

Max load Kn


45 98.15 69.10 6782.17 98.20 69.10 6785.62 6782.17 34.10 5.03

67 97.50 67.75 6605.63 97.35 67.75 6595.46 6595.46 28.00 4.25

58 101.00 67.75 6842.75 101.35 67.75 6866.46 6842.75 31.70 4.63

22 100.75 68.75 6926.56 99.30 68.75 6826.88 6826.88 14.90 2.18

26 99.50 68.80 6845.60 99.90 68.80 6873.12 6845.60 31.60 4.62

14 100.80 68.10 6864.48 100.95 68.42 6907.00 6864.48 47.30 6.89

56 99.00 66.20 6553.80 99.15 66.15 6558.77 6553.80 30.60 4.67

49 100.50 67.75 6808.88 100.65 67.70 6814.01 6808.14 31.80 4.67

2 97.65 67.60 6601.14 97.80 67.68 6619.10 6601.14 35.90 5.44

50 98.80 71.00 7014.80 98.90 70.95 7016.96 7014.80 17.60 2.51

Sample 4

24 100.50 67.25 6758.63 100.25 67.30 6746.83 6746.83 36.50 5.41

19 100.35 67.10 6733.49 100.20 67.25 6738.45 6733.49 36.10 5.36

20 101.25 67.00 6783.75 100.25 66.85 6701.71 6701.71 34.40 5.13

3 99.50 66.70 6636.65 99.25 66.60 6610.05 6610.05 41.00 6.20

7 98.80 66.50 6570.20 99.30 66.75 6628.28 6570.20 26.70 4.06

45 98.15 69.10 6782.17 98.20 69.10 6785.62 6782.17 34.10 5.03

67 97.50 67.75 6605.63 97.35 67.75 6595.46 6595.46 28.00 4.25

58 101.00 67.75 6842.75 101.35 67.75 6866.46 6842.75 31.70 4.63

22 100.75 68.75 6926.56 99.30 68.75 6826.88 6826.88 34.90 5.11

26 99.50 68.80 6845.60 99.90 68.80 6873.12 6845.60 31.60 4.62

Sample 5

83 99.70 67.30 6709.81 99.75 66.75 6658.31 6658.31 70.80 10.63

96 99.50 67.25 6691.38 99.00 67.25 6657.75 6657.75 37.30 5.60

79 100.25 67.00 6716.75 100.00 67.00 6700.00 6700.00 28.70 4.28

65 99.25 66.25 6575.31 98.55 66.60 6563.43 6563.43 47.10 7.18

71 100.75 67.00 6750.25 100.25 67.00 6716.75 6716.75 37.00 5.51

86 99.50 67.25 6691.38 99.80 67.60 6746.48 6691.38 76.40 11.42

74 98.80 66.75 6594.90 99.10 66.50 6590.15 6590.15 50.30 7.63

80 100.00 67.25 6725.00 100.25 66.65 6681.66 6681.66 44.50 6.66

91 100.80 67.00 6753.60 100.25 67.30 6746.83 6746.83 40.80 6.05

75 98.30 66.10 6497.63 97.75 66.25 6475.94 6475.94 49.00 7.57

Sample 6

1 98.55 67.95 6696.47 97.25 67.55 6569.24 6569.24 29.60 4.51

2 100.15 67.30 6740.10 100.25 67.85 6801.96 6740.10 37.90 5.62

3 100.10 68.20 6826.82 99.85 68.25 6814.76 6814.76 26.80 3.93

4 96.45 67.70 6529.67 98.55 68.05 6706.33 6529.67 30.80 4.72

5 100.22 67.55 6769.86 100.34 67.95 6818.10 6769.86 28.60 4.22

6 98.73 68.10 6723.51 99.96 68.55 6852.26 6723.51 33.60 5.00

7 99.55 69.10 6878.91 98.99 68.56 6786.75 6786.75 31.70 4.67

8 100.33 68.44 6866.59 98.95 67.99 6727.61 6727.61 21.20 3.15

9 97.10 69.99 6796.03 100.22 67.89 6803.94 6796.03 20.20 2.97

10 98.60 67.95 6699.87 99.00 68.30 6761.70 6699.87 46.00 6.87

196

FACING BRICK – HEADER FACE Sample 7 Dimension 1 (mm) Dimension 2 (mm) Brick


Area 1 mm2

Length Width

Area 2 mm2

Smaller area mm2

Max load Kn


79 99.45 66.25 6588.56 99.95 66.90 6686.66 6588.56 36.00 5.46

80 99.50 66.30 6596.85 99.80 66.70 6596.85 6596.85 15.80 2.40

58 99.75 67.50 6733.13 99.75 67.40 6723.15 6723.15 21.30 3.17

73 99.75 66.70 6653.33 99.65 66.55 6631.71 6631.71 24.80 3.74

78 100.05 67.00 6703.35 100.45 66.85 6715.08 6703.35 37.23 5.55

66 98.25 67.00 6582.75 99.10 67.00 6639.70 6582.75 20.80 3.16

63 99.70 66.30 6610.11 99.45 66.25 6588.56 6588.56 28.00 4.25

53 98.50 66.55 6555.18 98.80 66.75 6594.90 6555.18 37.00 5.64

55 97.25 64.75 6296.94 99.25 66.55 6605.09 6296.94 4.70 0.75

69 99.25 67.00 6649.75 99.50 67.50 6716.25 6649.75 19.60 2.95

Sample 8

40 100.60 67.75 6815.65 100.25 68.00 6817.00 6815.65 57.00 8.36

45 97.75 66.85 6534.59 97.50 66.75 6508.13 6508.13 58.00 8.91

15 98.25 66.20 6504.15 98.50 66.10 6510.85 6504.15 36.00 5.53

35 99.00 67.00 6633.00 99.35 67.25 6681.29 6633.00 40.00 6.03

37 98.50 67.00 6599.50 97.00 66.10 6411.70 6411.70 47.00 7.33

1 100.50 66.75 6708.38 100.35 66.85 6708.40 6708.38 43.00 6.41

20 100.00 66.85 6685.00 100.55 66.85 6721.77 6685.00 41.00 6.13

8 99.65 66.90 6666.59 99.95 67.00 6696.65 6666.59 46.00 6.90

9 99.90 66.45 6638.36 99.35 66.50 6606.78 6606.78 32.00 4.84

24 99.70 66.75 6654.98 99.45 66.50 6613.43 6613.43 38.00 5.75

197

COMMON BRICKS – BED FACE Sample 1 Dimension 1 (mm) Dimension 2 (mm) Brick


Area 1 mm2

Length Width

Area 2 mm2

Smaller area mm2

Max load Kn


- 216.10 99.25 21447.93 216.20 99.50 21511.90 21447.93 825.30 38.48 - 215.90 97.45 21039.46 215.50 97.45 21000.48 21000.48 829.30 39.49 - 217.50 100.05 21760.88 217.45 100.25 21799.36 21760.88 631.30 29.01 - 218.55 99.15 21669.23 219.05 99.95 21894.05 21669.23 866.30 39.98 - 217.85 98.95 21556.26 217.70 101.45 22085.67 21556.26 671.30 31.14 - 217.25 100.80 21898.80 217.25 101.20 21985.70 21898.80 791.30 36.13 - 217.95 99.65 21718.72 217.70 100.25 21824.43 21718.72 546.30 25.15 - 219.20 101.25 22194.00 219.25 100.40 22012.70 22012.70 866.30 39.35 - 218.80 100.85 22065.98 219.45 101.20 22208.34 22065.98 613.30 27.79 - 219.00 100.65 22042.35 219.50 101.50 22279.25 22042.35 750.30 34.04

- 214.75 100 21475 215.7 99.75 21516.075 21475 850 39.58 - 214.25 100.75 21585.688 213.85 100.00 21385 21385 813 38.02 - 215.50 100.8 21722.4 215.55 100.75 21716.663 21716.66 783 36.06 - 214.55 100.25 21508.638 215.5 99.45 21431.475 21431.48 582 27.16 - 214.90 100.75 21651.175 215.10 100.70 21660.57 21651.18 855 39.49 - 216.55 100.75 21817.413 216.25 100.95 21830.438 21817.41 730 33.46 - 216.00 100.25 21654.00 216.45 101.00 21861.45 21654 543 25.08 - 216.25 100.5 21733.125 216.15 100.15 21647.423 21647.42 786 36.31 - 216.20 100.75 21782.15 216.25 101.45 21938.563 21782.15 745 34.20

- 215.70 100.4 21656.28 215.5 99.90 21528.45 21528.45 695 32.28

Sample 3

- 216.20 99.05 21414.61 216.20 99.35 21479.47 21414.61 830.00 38.76

- 215.90 97.00 20942.30 215.50 97.45 21000.48 20942.30 790.00 37.72

- 216.50 100.25 21704.13 217.45 100.30 21810.24 21704.13 636.00 29.30

- 217.75 99.25 21611.69 219.05 99.95 21894.05 21611.69 840.00 38.87

- 217.85 98.35 21425.55 217.70 101.25 22042.13 21425.55 567.00 26.46

- 217.35 100.20 21778.47 217.25 101.20 21985.70 21778.47 794.00 36.46

- 218.20 99.15 21634.53 217.70 100.25 21824.43 21634.53 543.00 25.10

- 218.75 101.05 22104.69 219.25 100.40 22012.70 22012.70 833.00 37.84

- 218.80 100.85 22065.98 219.45 101.20 22208.34 22065.98 614.00 27.83

- 219.00 100.65 22042.35 219.50 101.50 22279.25 22042.35 749.00 33.98

Sample 4

- 216.00 98.60 21297.60 216.00 98.60 21297.60 21297.60 607.90 28.54 - 219.50 101.10 22191.45 219.50 101.35 22246.33 22191.45 573.90 25.86 - 214.25 98.35 21071.49 214.20 98.40 21077.28 21071.49 473.90 22.49 - 219.60 101.95 22388.22 219.20 101.80 22314.56 22314.56 562.90 25.23

- 218.20 101.30 22103.66 218.45 101.30 22128.99 22103.66 501.90 22.71

- 214.35 97.00 20791.95 214.40 97.55 20914.72 20791.95 512.90 24.67

- 217.20 101.45 22034.94 217.25 100.25 21779.31 21779.31 462.90 21.25

- 219.80 101.65 22342.67 220.15 101.55 22356.23 22342.67 544.90 24.39

- 217.45 100.45 21842.85 217.34 100.15 21766.60 21766.60 437.80 20.11

- 215.95 99.95 21584.20 215.35 99.75 21481.16 21481.16 475.90 22.15

198



Area 1 mm2

Length Width

Area 2 mm2

Smaller area mm2

Max load Kn


- 219.25 98.00 21486.50 219.20 101.20 22183.04 21486.50 452.10 21.04

- 220.55 100.65 22198.36 220.85 100.95 22294.81 22198.36 604.10 27.21

- 218.20 99.65 21743.63 218.40 100.15 21872.76 21743.63 851.10 39.14

- 220.25 100.25 22080.06 220.75 101.00 22295.75 21798.44 849.20 38.96

- 221.25 102.95 22777.69 221.25 103.75 22954.69 22070.73 744.20 33.72

- 221.40 101.60 22479.00 221.60 101.95 22592.12 21594.65 711.20 32.93

- 218.95 100.75 22306.05 219.30 100.85 22116.41 22004.88 779.20 35.41

- 220.00 100.95 22103.00 219.80 100.95 22188.81 21668.89 687.20 31.71

- 218.20 100.70 22154.00 218.45 100.45 21943.30 21003.52 824.20 39.24

- 219.30 100.00 21820.00 219.25 100.25 21979.81 21338.00 857.20 40.17

Sample 6

- 216.35 97.60 21115.76 216.00 98.00 21168.00 21115.76 434.90 20.60

- 218.50 100.10 21871.85 218.75 101.25 22148.44 21871.85 573.90 26.24

- 214.20 98.25 21045.15 214.25 98.45 21092.91 21045.15 400.80 19.04

- 219.55 101.95 22383.12 219.25 100.80 22100.40 22100.40 560.00 25.34

- 217.20 100.30 21785.16 218.40 101.30 22123.92 21785.16 502.80 23.08

- 214.05 97.35 20837.77 214.25 97.75 20942.94 20837.77 512.90 24.61

- 216.20 101.25 21890.25 217.30 100.25 21784.33 21784.33 450.90 20.70

- 218.80 100.65 22022.22 219.50 101.45 22022.22 14999.66 542.90 36.19

- 218.45 101.45 22161.75 217.00 100.55 21819.35 21819.35 400.80 18.37

- 215.05 99.95 21494.25 215.35 99.65 21459.63 21459.63 465.90 21.71

Sample 7

- 216.35 97.60 21115.76 216.00 98.00 21168.00 21115.76 625.03 29.60

- 218.50 100.10 21871.85 218.75 101.25 22148.44 21871.85 828.94 37.90

- 214.20 98.25 21045.15 214.25 98.45 21092.91 21045.15 564.01 26.80

- 219.55 101.95 22383.12 219.25 100.80 22100.40 22100.40 680.69 30.80

- 217.20 100.30 21785.16 218.40 101.30 22123.92 21785.16 623.05 28.60

- 214.05 97.35 20837.77 214.25 97.75 20942.94 20837.77 700.15 33.60

- 216.20 101.25 21890.25 217.30 100.25 21784.33 21784.33 690.56 31.70

- 218.80 100.65 22022.22 219.50 101.45 22268.28 22022.22 466.87 21.20

- 218.45 101.45 22161.75 217.00 100.55 21819.35 21819.35 440.75 20.20

- 215.05 99.95 21494.25 215.35 99.65 21459.63 21459.63 987.14 46.00

Sample 8

- 214.55 97.75 20972.26 215.00 98.25 21123.75 20972.26 872.50 41.60

- 213.45 96.80 20661.96 213.30 96.80 20647.44 20647.44 883.60 42.79

- 213.45 96.80 20661.96 213.30 97.45 20786.09 20661.96 751.60 36.38

- 216.00 98.70 21319.20 215.50 98.60 21248.30 21248.30 815.50 38.38

- 214.85 98.50 21162.73 215.00 98.50 21177.50 21162.73 876.60 41.42

- 215.00 98.00 21070.00 214.95 97.50 20957.63 20957.63 1017.60 48.56

- 212.25 98.00 20800.50 212.25 97.75 20747.44 20747.44 1032.60 49.77

- 217.00 99.75 21645.75 217.00 99.00 21483.00 21483.00 849.60 39.55

- 214.00 98.00 20972.00 214.95 97.75 21011.36 20972.00 913.60 43.56

- 212.45 96.25 20448.31 212.25 96.00 20376.00 20376.00 832.60 40.86

199



Area 1 mm2

Length Width

Area 2 mm2

Smaller area mm2

Max load Kn


- 216.36 96.75 20932.83 216.25 98.25 21246.56 20932.83 713.50 34.09

- 213.25 96.80 20642.60 213.30 96.80 20647.44 20642.60 793.60 38.44

- 210.30 97.80 20567.34 210.30 97.45 20493.74 20493.74 751.60 36.67

- 215.45 98.70 21264.92 215.50 98.60 21248.30 21248.30 758.50 35.70

- 214.85 98.50 21162.73 215.00 98.50 21177.50 21162.73 856.60 40.48

- 212.55 98.30 20893.67 214.95 97.50 20957.63 20893.67 988.60 47.32

- 212.25 98.00 20800.50 212.25 97.75 20747.44 20747.44 1015.60 48.95

- 217.00 99.75 21645.75 217.00 99.00 21483.00 21483.00 792.60 36.89

- 214.00 98.00 20972.00 214.95 97.75 21011.36 20972.00 953.60 45.47

- 212.45 96.25 20448.31 212.25 96.00 20376.00 20376.00 832.60 40.86

Sample 10

- 215.50 97.75 21065.13 215.75 97.55 21046.41 21046.41 1081.50 51.39

- 215.25 98.95 21298.99 214.90 98.00 21060.20 21060.20 1221.60 58.01

- 214.00 97.45 20854.30 214.10 97.50 20874.75 20854.30 1077.60 51.67

- 213.85 97.70 20893.15 214.15 97.95 20975.99 20893.15 1027.50 49.18

- 215.00 98.00 21070.00 215.00 98.00 21070.00 21070.00 1061.60 50.38

- 214.50 98.00 21021.00 214.35 98.25 21059.89 21021.00 1032.60 49.12

- 214.00 98.50 21079.00 214.65 97.25 20874.71 20874.71 980.60 46.98

- 214.70 97.75 20986.93 214.65 97.25 20874.71 20874.71 974.60 46.69

- 211.10 96.25 20318.38 211.25 96.35 20353.94 20318.38 958.60 47.18

- 215.40 98.35 21184.59 215.25 98.10 21116.03 21116.03 722.60 34.22

Sample 11

- 216.00 98.00 21168.00 216.25 98.25 21246.56 21168.00 813.80 38.44

- 215.90 97.35 21017.87 215.40 97.60 21023.04 21017.87 926.60 44.09

- 213.45 98.00 20918.10 213.75 99.15 21193.31 20918.10 928.00 44.36

- 214.95 97.60 20979.12 215.25 97.25 20933.06 20933.06 797.60 38.10

- 212.75 96.00 20424.00 213.00 96.00 20448.00 20424.00 1002.60 49.09

- 213.80 98.75 21112.75 214.25 98.00 20996.50 20996.50 948.60 45.18

- 212.00 96.65 20489.80 216.65 97.00 21015.05 20489.80 1001.60 48.88

- 214.45 98.35 21091.16 214.55 98.25 21079.54 21079.54 833.60 39.55

- 212.00 94.75 20087.00 212.20 95.75 20318.15 20087.00 967.60 48.17

- 216.00 97.25 21006.00 215.75 97.00 20927.75 20927.75 691.60 33.05

Sample 12

- 213.00 96.95 20650.35 213.50 97.75 20869.63 20650.35 1003.50 48.59

- 215.75 99.65 21499.49 215.45 99.30 21394.19 21394.19 740.60 34.62

- 212.25 96.95 20577.64 212.00 97.25 20617.00 20577.64 914.60 44.45

- 212.95 97.25 20709.39 213.00 97.25 20714.25 29709.39 765.50 25.77

- 217.40 98.75 21468.25 217.95 98.50 21468.08 21468.08 899.60 41.90

- 212.60 97.35 20696.61 212.55 96.90 20596.10 20596.10 1032.60 50.14

- 214.25 98.75 21157.19 214.20 98.75 21152.25 21152.25 952.60 45.04

- 215.10 99.00 21294.90 215.35 99.25 21373.49 21294.90 930.60 43.70

- 214.40 97.75 20957.60 214.90 97.30 20909.77 20909.77 870.60 41.64

- 215.40 98.35 21184.59 215.25 98.10 21116.03 21116.03 722.60 34.22

B

STATISTICAL TABLES

201

Table B1: 5 per cent points of the F-distribution (Adapted from Loveday, 1975)

1ν = 1 2 3 4 5 6 7 8 10 12 24 ∞ 2ν = 1 161.4 199.5 215.7 224.6 230.2 234.0 236.8 238.9 241.9 243.9 249.0 254.3

2 18.5 19.0 19.2 19.2 19.3 19.3 19.4 19.4 19.4 19.4 19.5 19.5 3 10.13 9.55 9.28 9.12 9.01 8.94 8.89 8.85 8.79 8.74 8.64 8.53 4 7.71 6.94 6.59 6.39 6.26 6.16 6.09 6.04 5.96 5.91 5.77 5.63

5 6.61 5.79 5.41 5.19 5.05 4.95 4.88 4.82 4.74 4.68 4.53 4.36 6 5.99 5.14 4.76 4.53 4.39 4.28 4.21 4.15 4.06 4.00 3.84 3.67 7 5.59 4.74 4.35 4.12 3.97 3.87 3.79 3.73 3.64 3.57 3.41 3.23 8 5.32 4.46 4.07 3.84 3.69 3.58 3.50 3.44 3.35 3.28 3.12 2.93 9 5.12 4.26 3.86 3.63 3.48 3.37 3.29 3.23 3.14 3.07 2.90 2.71

10 4.96 4.10 3.71 3.48 3.33 3.22 3.14 3.07 2.98 2.p1 2.74 2.54 11 4.84 3.98 3.59 3.36 3,20 3.09 3.01 2.95 2.85 2.79 2.61 2.40 12 4.75 3.89 3.49 3.26 3.11 3.00 2.91 2.85 2.75 2.69 2.51 2.30 13 4.67 3.81 3.41 3.18 3.03 2.92 2.83 2.77 2.67 2.60 2.42 2.21 14 4.60 3.74 3.34 3.11 2.96 2.85 2.76 2.70 2.60 2.53 2.35 2.13

15 4.54 3.68 3.29 3.06 2.90 2.79 2.71 2.64 2.54 2.48 2.29 2.07 16 4.49 3.63 3,.24 3.01 2.85 2.74 2.66 2.59 2.49 2.42 2.24 2.01 17 4.45 3.59 3.20 2.96 2.81 2.70 2.61 2.55 2.45 2.38 2.19 1.96 18 4.41 3.55 3.16 2.93 2.77 2.66 2.58 2.51 2.41 2.34 2.15 1.92 19 4.38 3.52 3.13 2.90 2.74 2.63 2.54 2.48 2.38 2.31 2.11 1.88

20 4.35 3.49 3.10 2.87 2.71 2.60 2.51 2.45 2.35 2.28 2.08 1.84 21 4.32 3.47 3.07 2.84 2.68 2.57 2.49 2.42 2.32 2.25 2.05 1.81 22 4.30 3.44 3.05 2.82 2.66 2.55 2.46 2.40 2.30 2.23 2.03 1.78 23 4.28 3.42 3.03 2.80 2.64 2.53 2.44 2.37 2.27 2.20 2.00 1.76 24 4.26 3.40 3.01 2.78 2.62 2.51 2.42 2.36 2.25 2.18 1.98 1.73

25 4.24 3.39 2.99 2.76 2.60 2.49 2.40 2.34 2.24 2.16 1.96 1.71 26 4.23 3.37 2.98 2.74 2.59 2.47 2.39 2.32 2.22 2.15 1.95 1.69 27 4.21 3.35 2.96 2.73 2.57 2.46 2.37 2.31 2.20 2.13 1.93 1.67 28 4.20 3.34 2.95 2.71 2.56 2.45 2.36 2.29 2.19 2.12 1.91 1.65 29 4.18 3.33 2.93 2.70 2.55 2.43 2.35 2.28 2.18 2.10 1.90 1.64

30 4.17 3.32 2.92 2.69 2.53 2.42 2.33 2.27 2.16 2.09 1.89 1.62 32 4.15 3.29 2.90 2.67 2.51 2.40 2.31 2.24 2.14 2.07 1.86 1.59 34 4.13 3.28 2.88 2.65 2.49 2.38 2.29 2.23 2.12 2.05 1.84 1.57 36 4.11 3.26 2.87 2.63 2.48 2.36 2.28 2.21 2.11 2.03 1.82 1.55 38 4.10 3.24 2.85 2.62 2.46 2.35 2.26 2.19 2.09 2.02 1.81 1.53

40 4.08 3.23 2.84 2.61 2.45 2.34 2.25 2.18 2.08 2.00 1.79 1.51 60 4.00 3.15 2.76 2.53 2.37 2.25 2.17 2.10 1.99 1.92 1.70 1.39

120 3.92 3.07 2.68 2.45 2.29 2.18 2.09 2.02 1.91 1.83 1.61 1.25 ∞ 3.84 3.00 2.60 2.37 2.21 2.10 2.01 1.94 1.83 1.75 1.52 1.00

202

Table B2: Distribution of tc (Adapted from Kennedy and Neville, 1985)

Probability, α Degrees of

freedom (df) 0.10 0.05 0.01 0.001 1 6.314 12.706 63.657 636.619 2 2.920 4.303 9.925 31.598 3 2.353 3.182 5.841 12.941 4 2.12 2.776 4.604 8.610 5 2.015 2.571 4.032 6.859 6 1.943 2.447 3.707 5.959 7 1.895 2.365 3.499 5.405 8 1.860 2.306 3.355 5.041 9 1.833 2.262 3.250 4.781

10 1.812 2.228 3.169 4.587 11 1.796 2.201 3.106 4.437 12 1.782 2.179 3.055 4.318 13 1.771 2.160 3.012 4.221 14 1.761 2.145 2.977 4.140 15 1.753 2.131 2.947 4.073 16 1.746 2.120 2.921 4.015 17 1.740 2.110 2.898 3.965 18 1.734 2.101 2.878 3.922 19 1.729 2.093 2.861 3.883 20 1.725 2.086 2.845 3.850 21 1.721 2.080 2.831 3.819 22 1.717 2.074 2.819 3.792 23 1.714 2.069 2.807 3.767 24 1.711 2.064 2.797 3.745 25 1.708 2.060 2.787 3.725 26 1.706 2.056 2.779 3.707 27 1.703 2.052 2.771 3.690 28 1.701 2.048 2.763 3.674 29 1.699 2.045 2.756 3.659 30 1.697 2.042 2.750 3.646 40 1.684 2.021 2.704 3.551 60 1.671 2.000 2.660 3.460

120 1.658 1.980 2.617 3.373 ∞ 1.645 1.960 2.576 3.290

203

Table B3: Range coefficient d (Adapted from Kennedy and Neville, 1985)

Number of observations,

n

Coefficient, d

Number of observations,

n

Coefficient,

d 2 0.8862 14 0.2935 3 0.5908 15 0.2880 4 0.4857 16 0.2831 5 0.4299 17 0.2787 6 0.3945 18 0.2747 7 0.3698 19 0.2711 8 0.3512 20 0.2677 9 0.3367 24 0.2567 10 0.3249 50 0.2223 11 0.3152 100 0.1994 12 0.3069 1000 0.1543 13 0.2998

Table B.4: Factors for control lines for mean and range charts values (BS 2846:1991)

For mean For range

Warning line

Action line

Lower action

line

Lower warning

line

Upper warning

line

Upper action

line

Number in subgroup

n

'0.025 A '

0.001A '0.999D '

0.975D '0.025D '

0.001D 2 1.229 1.937 0.00 0.04 2.81 4.12 3 0.668 1.054 0.04 0.18 2.17 2.99 4 0.476 0.750 0.10 0.29 1.93 2.58 5 0.377 0.594 0.16 0.37 1.81 2.36 6 0.316 0.498 0.21 0.42 1.72 2.22 7 0.274 0.432 0.26 0.46 1.66 2.12 8 0.244 0.384 0.29 0.5 1.62 2.04 9 0.220 0.347 0.32 0.52 1.58 1.99 10 0.202 0.317 0.35 0.54 1.55 1.94 11 0.186 0.294 0.38 0.56 1.53 1.90

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