UNIVERSITY OF NAIROBI

INVESTIGATING THE EFFECTS OF THE REPLACEMENT

OF SAND WITH QUARRY DUST ON THE PROPERTIES OF

CONCRETE

By:

Maina Simon Karanja

F16/36072/2010

A Project submitted in partial fulfillment of the requirement for the

award of the degree of

BACHELORS OF SCIENCE IN CIVIL ENGINEERING

2015

i

Abstract

Sand collected from natural deposit is expensive due to unwanted cost of transportation from

sources. Large scale exploitation of natural sand creates environmental impact on society.

River sand is most commonly used fine aggregate in concrete but due to acute shortage in

many areas, availability, cost & environmental impact are the major concern. To overcome

from this crisis, partial/full replacement of sand with quarry dust can be an economic

alternative. In developing countries like Kenya, quarry dust has been rampantly used in

different construction purposes but replacement technology has emerged as an innovative

development to civil engineering material.

Design mix of class 25 grade concrete with replacement of 0%, 25%, 50%, 75%, and 100%

of quarry have been considered for laboratory analysis of Slump test, compaction factor

test, compressive strength, split tensile strength and flexural strength.

ii

Dedication

First, I dedicate this research work to Almighty God who has brought me this far.

Second, my dedication goes to my Lecturers, family members, fellow students and friends for

their support and guidance throughout this project.

iii

Acknowledgements

An undertaking of this magnitude cannot be successfully achieved by the unilateral efforts of one

individual. I would wish to express my sincere gratitude first and foremost to God for His divine

guidance throughout my life and my five years in campus, my supervisor Dr. (Eng.) Monica

Wokabi for her immense support, encouragement and guidance during practical and report

writing without whom this work could not have been realized, To my parents Mr. & Mrs. Maina

who gave me financial and moral support that has seen me through my degree course and finally

to the technicians in the concrete laboratory who went out of their way to assist me finish my

tests on schedule.

iv

Table of Contents Abstract ....................................................................................................................................... i

Dedication .................................................................................................................................. ii

Acknowledgements .................................................................................................................. iii

List of tables .............................................................................................................................. vi

List of plates ............................................................................................................................. vii

List of graphs ......................................................................................................................... viii

CHAPTER 1 INTRODUCTION ............................................................................................. 1

1.1 Background ...................................................................................................................... 1

1.2 PROBLEM STATEMENT .............................................................................................. 2

1.3 PURPOSE OF THE STUDY ........................................................................................... 2

1.3.1 OVERALL OBJECTIVE .............................................................................................. 2

1.3.2 SPECIFIC OBJECTIVES.......................................................................................... 2

1.4 RESEARCH HYPOTHESIS ........................................................................................... 2

1.5 SIGNIFICACE OF THE STUDY .................................................................................... 3

1.6 DELIMITATIONS OF THE STUDY ............................................................................. 3

1.7 LIMITATION OF THE STUDY ..................................................................................... 3

CHAPTER 2 LITERATURE REVIEW .................................................................................... 4

2.1OVERVIEW...................................................................................................................... 4

2.2 CLASSIFICATION OF AGGREGATE .......................................................................... 5

2.3FINE AGGREGATE......................................................................................................... 6

2.3.1 CHARACTERISTICS ............................................................................................... 6

2.3.2 UTILIZATION APPLICATIONS .......................................................................... 10

2.4 RIVER SAND ................................................................................................................ 11

2.4.1 PRODUCTION ....................................................................................................... 11

2.4.2 PROPERTIES OF RIVER SAND ........................................................................... 11

2.5 QUARRY DUST............................................................................................................ 12

2.5.1 PRODUCTION ........................................................................................................... 12

2.5.2 PROPERTIES OF QUARRY DUST ...................................................................... 13

2.5.3 UTILIZATION APPLICATION ............................................................................. 14

2.5.4 EFFECTS OF QUARRY DUST ON ENVIRONMENT ........................................ 15

2.5.5 OBSTACLES TO UTILIZATION .......................................................................... 15

2.6 DESIGN OF CONCRETE MIXES................................................................................ 15

v

2.6.1 PRINCIPLES OF DESIGN ..................................................................................... 16

2.6.2 STAGES IN MIX DESIGN .................................................................................... 17

2.7 BATCHING OF CONCRETE MATERIALS ............................................................... 18

2.8 PROPERTIES OF CONCRETE. ................................................................................... 18

2.8.1 PROPERTIES OF FRESH CONCRETE ................................................................ 18

2.8.3 PROPERTIES OF CONCRETE. ............................................................................ 21

2.9 STANDARDS FOR FINE AGGREGATE .................................................................... 24

CHAPTER 3 RESEARCH METHODOLOGY ...................................................................... 26

3.1 SAMPLE COLLECTION, PREPARATION AND ASSESSMENT ............................ 26

Grading ............................................................................................................................. 27

3.2 SLUMP TEST ................................................................................................................ 28

3.3 COMPACTING FACTOR TEST .................................................................................. 28

3.4 DETERMINATION OF COMPRESSIVE STRENGTH .............................................. 30

3.5 INDIRECT TENSILE TEST ACCORDING TO BS1881-117:1983 ............................ 31

3.6 FLEXURAL STRENGTH TEST TO BS 1881:118 – 1983 .......................................... 33

3.7 Preparation of hollow fencing post ................................................................................ 35

CHAPTER 4.0 RESULTS, DATA ANALYSIS AND DISCUSSION ................................... 37

4.1 Sieve analysis ................................................................................................................. 37

4.2 Workability..................................................................................................................... 40

4.3 Compressive strength ..................................................................................................... 42

4.4 Tensile strength .............................................................................................................. 44

4.5 Flexural strength ............................................................................................................. 47

4.6 Cost Benefit Analysis ..................................................................................................... 48

6. Conclusion and recommendation ......................................................................................... 51

6.1 Conclusion ...................................................................................................................... 51

6.2 Recommendation ............................................................................................................ 52

REFERENCES ........................................................................................................................ 53

Appendix .................................................................................................................................. 54

THE MIX DESIGN PROCESS ............................................................................................... 54

vi

List of tables Table 1: slump, compaction and workability relationship ....................................................... 16

Table 2: Slump test for all ratios .............................................................................................. 28

Table 3: Compaction factor of different ratios ........................................................................ 29

Table 4: Summary of Average cube Crushing Strengths at 7 days ......................................... 31

Table 5: Summary of Average cube Crushing Strengths at 28 days ....................................... 31

Table 6: Seven days tensile Strengths ...................................................................................... 32

Table 7: Twenty eight tensile Strengths................................................................................... 33

Table 8: Flexural test results .................................................................................................... 35

Table 9: sieve analysis of coarse aggregate ............................................................................. 37

Table 10: sieve analysis of river sand ...................................................................................... 38

Table 11: sieve analysis of quarry dust .................................................................................... 39

Table 12: batching ratio 1:1.5:3(cement: fine aggregate: coarse aggregate) ........................... 40

Table 13: compaction factor of different ratios ....................................................................... 40

Table 14: slump test for the all ratios....................................................................................... 41

Table 15: Summary of Average cube Crushing Strengths at 7 days ....................................... 42

Table 16: Summary of Average cube Crushing Strengths at 28 days ..................................... 43

Table 17: batching ratio 1:1.5:3(cement: fine aggregate: coarse aggregate) ........................... 44

Table 18: seven days’ tensile Strengths ................................................................................... 44

Table 19: twenty eight day tensile strength ............................................................................. 45

Table 20: 5 twenty eight day flexural strength of beams ......................................................... 47

Table 21: mass of different ratios ............................................................................................ 48

Table 22: Costs of different replacement ................................................................................. 49

vii

List of plates Plate 1: Arrangement of different size of sieves ........................................................................ 8

Plate 2: particle size distribution graph ........................................................................................

Plate 3: shape and texture of aggregate (2) .............................................................................. 10

Plate 4: quarry dust production (7) .......................................................................................... 13

Plate 5: Typical quarry dust ..................................................................................................... 14

Plate 6: Typical quarry dust ..................................................................................................... 16

Plate 7: slump test .................................................................................................................... 19

Plate 8: compaction factor apparatus ....................................................................................... 20

Plate 9: casted cubes ready to be remolded and cured ............................................................. 21

Plate 10: cylinder in compression machine ready to be crushed ............................................. 22

Plate 11: conducting of flexural test ........................................................................................ 23

Plate 12: Arrangement of loading of test specimen (centre-point loading) ............................. 34

Plate 13: 100% sand replacement hollow fencing post ........................................................... 36

viii

List of graphs Graph 1: sieve analysis of coarse aggregate ............................................................................ 37

Graph 2: river sand sieve analysis ........................................................................................... 38

Graph 3: quarry dust sieve analysis ......................................................................................... 39

Graph 4: seven days compressive strength .............................................................................. 42

Graph 5: twenty eight days compressive strength ................................................................... 43

Graph 6: seven days tensile strength ........................................................................................ 45

Graph 7: twenty eight day tensile strength .............................................................................. 46

Graph 8:twenty eight day flexural strength ............................................................................. 47

Graph 9: Graph of total prices against the quarry .................................................................... 49

1

CHAPTER 1 INTRODUCTION

1.1 Background

Concrete is the most widely used composite material today. The constituents of concrete are

coarse aggregate, fine aggregate, binding material and water. Rapid increase in construction

activities leads to acute shortage of conventional construction materials. The function of the

fine aggregate is to assist in producing workability and uniformity in the mixture. It is

conventional that sand is being used as fine aggregate in concrete. This is due to the ease of

acquisition and its well-graded nature and that all sizes of grains are well distributed in a

given sample. The application of river sand is mainly for all kinds of civil engineering

construction.

The annual sand demand for the construction industry in Kenya and other developing

countries is high and all is obtained from major rivers. (1)

The excessive excavation of river sand is becoming a serious environmental problem.

Erosion and failure of river banks, lowering of river beds and damage of structures situated

closer to the rivers, saline water intrusion into the land and coastal erosion are the major

adverse effects due to intensive river sand mining. The demand for natural sand is also quite

high in developing countries owing to rapid infrastructural growth which results to scarcity of

natural sand. Therefore, construction industries of developing countries are in stress to

identify alternative materials to replace the demand for natural sand.

In the future, the entire construction industry may come to a halt if there are no alternative

sources of sand. Therefore, it is necessary to explore the possibilities for alternative sources

to minimize river sand extraction.

At present, the identified alternative sources are fibre glass as partial replacement, wood ash,

saw dust, recycled concrete and fly ash. They are not effective because of their quantity and

they also have low workability. Quarry dust has been proposed as an alternative to river sand.

Quarries are operating in many parts of Kenya to supply coarse aggregates for various types

of construction, especially for concrete, road construction and foundations of buildings. The

advantages of utilization of byproducts or aggregates obtained as waste materials are

pronounced in the aspects of reduction in environmental load & waste management cost,

reduction of production cost as well as augmenting the quality of concrete. (2)

2

1.2 PROBLEM STATEMENT

The quarry dust, the by-product, was never used before instead of river sand earlier because

of the different quality. Various rock types produce different types or different qualities of

quarry dusts due to the inclusion of their fresh minerals. Also, it has no uniformity and

similarity to river sand. Although now it is used for road work the industry people are afraid

to use it for concrete or such strong constructions due to the higher percentages of minerals

other than quartz. Therefore, detailed studies on quarry dusts are needed to find out their

suitability.

The research will focus on the use of quarry dust as replacement for aggregates in concrete. It

will investigate the compression strength properties of concrete containing quarry dust and

the application of quarry dust concrete in construction of fencing posts. (2)

1.3 PURPOSE OF THE STUDY

1.3.1 OVERALL OBJECTIVE

To investigate the possibility of either partial or total replacement of fine aggregates with

quarry dust in the manufacture of concrete blocks and hollow fencing posts.

1.3.2 SPECIFIC OBJECTIVES

i) To investigate the compressive, tensile and flexural strength of concrete made

using quarry dust as fine aggregate.

ii) To investigate changes in strength of concrete as river sand is replaced with

quarry dust in different percentages.

iii) To investigate the effect of quarry dust on the workability of concrete in different

proportions.

iv) To test practical application of quarry dust concrete in construction of a hollow

fencing posts

v) To assess the cost implications of using quarry dust in concrete manufacture as

compared to river sand.

1.4 RESEARCH HYPOTHESIS

The compression strength of concrete depend on ratio of mixtures (cement, fine aggregate

and course aggregate) and water-cement ratio, quarry dust has small particles than river sand

so requires less water-cement ratio hence concrete compression strength is expected to

improve when river sand is replaced with quarry dust.

3

There is direct relationship between properties of river sand (density, void ratio and particle

size) and properties of quarry dust hence one cannot only use quarry dust as a partial

replacement of river sand but also as full replacement of river sand.

1.5 SIGNIFICACE OF THE STUDY

This research will help determine strength of concrete produced with quarry dust hence it will

be easier for engineers to specify in which projects and in what proportions quarry dust will

be used.

The research will increase development in areas with little or no access to river sand for

quarry dust will be used in replacement during constructions.

There is need for this research since quarry dust has recently gained good attention to be used

as an effective filler material instead of sand. Some construction companies tend to use it

without the knowledge of its strength which results to risk of failure of structures.

1.6 DELIMITATIONS OF THE STUDY

Apart from preparation of cubes, samples of hollow fencing posts are prepared to examine

the workability of the research. The post cross section area is a cube 120 mm length by 120

mm width, with a hollow 55 mm diameter and a height of 2000 mm.

1.7 LIMITATION OF THE STUDY

Time factor is the major limitation of this project because testing for the durability of hollow

post required much time in order for one to come up with conclusive reports.

Quarry dust is obtained from rocks with different chemical properties hence there may be no

specific compression strength for concrete produced by different quarry dust.

4

CHAPTER 2 LITERATURE REVIEW

2.1OVERVIEW

Aggregates are widely used as a base material for foundations and as an ingredient in

Portland cement concrete and asphalt concrete. While the geological classification of

aggregates gives insight into the properties of the material, the suitability of a specific source

of aggregates for a particular application requires testing and evaluation.

Civil engineers select aggregates for their ability to meet specific project requirements, rather

than their geologic history. The physical and chemical properties of the rocks determine the

acceptability of an aggregate source for a construction project. These characteristics vary

within a quarry or gravel pit, making it necessary to sample and test the materials continually

as the aggregates are being produced.

Rapid increase in construction activities leads to acute shortage of aggregates especially fine

aggregate resulting to research of finding other better materials to be used as replacements.

Some of the projects are;

1. Partial replacement of river sand with fly ash.

The conclusion of experiment was that Fly ash is a byproduct that can be used in concrete to

obtain durability, cost, and environmental benefits. Increase of amount of fly ash reduces

workability of the concrete. (3)

2. Properties of concrete containing saw dust as fine aggregate

There was reduction in strength of concrete with sawdust as fine aggregate due to its higher

rate of water absorption because the higher the water contents in concrete, the lower the

strength of the concrete. Optimum replacement of sawdust with sand was found to be 25%

beyond the limit, which did not meet the code requirement for strength BS 1881 part4 (1970).

(3)

3. Use of wood ash as fine aggregate in production of concrete

The conclusion was wood ash is suitable for use in concrete making. The water requirement

increases as the ash content increases. Compressive and tensile strength of concrete mix

increases with age of curing and decreases as the ash content increases. The Flexural strength

of the beam of the concrete for all mix increases with age of curing and decreases as the ash

content increases. Ash is available in insignificant quantities as a waste and can be utilized

for making concrete. (3)

4. Utilization of Industrial Waste Slag as fine aggregate in Concrete Applications

The results indicated that compressive strength was higher by 4 to 6% in mixes at all ages for

the re- placement levels in-between 30% to 50%. Strength reduction was observed at 100%

replacement of fine aggregate with granular slag by 7% to 10% which was attributed to the

coarser particles that affected cohesive properties of concrete. (3)

5

5. Use of rice husks as fine aggregate in production of concrete

From the investigations the following conclusions were be made: There exists a high

potential for the use of rice husk as fine aggregate in the production of lightly reinforced

concrete. Weight-Batched Rice Husk Concrete and Volume-Batched Rice Husk Concrete

show similar trends in the variation of bulk density, workability and compressive strength.

Loss of bulk density, workability and compressive strength is higher for Weight-Batched

Rice Husk Concrete than Volume-Batched Rice Husk Concrete. (3)

6. Use of crushed granite fine as replacement of river sand in concrete production

Based on the results of the experiment, conclusions were: The physical and chemical

properties of granite fines had satisfied the requirement of code provisions. The other strength

and durability test conducted shows that the granite fines is fit to be used in concrete mixes.

(3)

2.2 CLASSIFICATION OF AGGREGATE

Aggregates can be divided into several categories according to different criteria.

a) in accordance with size:

Coarse aggregate: Aggregates predominately retained on the No. 4 (4.75 mm) sieve. For mass

concrete, the maximum size can be as large as 150 mm.

Fine aggregate (sand): Aggregates passing No.4 (4.75 mm) sieve and predominately retained

on the No. 200 (75 μm) sieve.

b) In accordance with sources:

Natural aggregates: This kind of aggregate is taken from natural deposits without changing

their nature during the process of production such as crushing and grinding. Some examples

in this category are sand, crushed limestone, and gravel.

Manufactured (synthetic) aggregates: This is a kind of man-made materials produced as a

main product or an industrial by-product. Some examples are blast furnace slag, lightweight

aggregate (e.g. expanded perlite), and heavy weight aggregates (e.g. iron ore or crushed

steel).

c) In accordance with unit weight

Light weight aggregate: The unit weight of aggregate is less than 1120 kg/m3

. The

corresponding concrete has a bulk density less than 1800 kg/m3

. (Cinder, blast-furnace slag,

volcanic pumice).

Normal weight aggregate: The aggregate has unit weight of 1520-1680 kg/m3

. The concrete

made with this type of aggregate has a bulk density of 2300-2400 kg/m3

.

Heavy weight aggregate: The unit weight is greater than 2100 kg/m3

. The bulk density of the

corresponding concrete is greater than 3200 kg/m3

. A typical example is magnetite limonite,

a heavy iron ore. Heavy weight concrete is used in special structures such as radiation

shields. (4)

6

2.3FINE AGGREGATE

2.3.1 CHARACTERISTICS

Many properties of fine aggregate are derive from its parent rock:

1. Physical properties such as Porosity, absorption, surface moisture, Particle shape, Particle

surface texture and Permeability.

2. Mechanical properties such as relative density, strength, stiffness, hardness, permeability

and pore structure.

3. Chemical such as mineral composition, Alkali–aggregate reactivity and Sulphate

soundness.

Thus the origin of the parent rock is very important. Rocks themselves are comprised of

various minerals, defined as ‘naturally occurring inorganic substances of more or less definite

chemical composition and usually of a specific crystalline structure’. Rocks of the earth’s

crust are generally classified as igneous, sedimentary, or metamorphic, relating to their

origin. (5)

2.3.1.1 Moisture content

2.3.1.1.1 Moisture content in aggregate

The moisture condition of aggregates refers to the presence of water in the pores and on the

surface of aggregates. There are four different moisture conditions:

a) Oven Dry (OD): This condition is obtained by keeping aggregates at temperature of 1100

C

for a period of time long enough to reach a constant weight.

b) Air Dry (AD): This condition is obtained by keeping aggregates under room temperature

and humidity. Pores inside the aggregate are partly filled with water.

c) Saturated Surface Dry (SSD): In this situation the pores of the aggregate are fully filled

with water and the surface is dry. This condition can be obtained by

immersion in water for 24 hours following by drying of the surface

with wet cloth.

d) Wet (W): The pores of the aggregate are fully filled with water and the surface of

aggregate is covered with a film of water. Saturated Oven Dry

Concrete properties at both the fresh and hardened states are strongly affected by the water

content, it is very important to ensure that the right amount of water is added to the mix. The

moisture content under saturated surface dry condition is used as reference because that is an

equilibrium condition at which the fine aggregates will neither absorb water nor give up

water to the paste. Thus, if moisture content value for a batch of fine aggregates is positive,

there is surface moisture on the aggregates. If it is negative, it means that the pores in fine

aggregates are only partly filled with water. Since the fine aggregates may give out or absorb

water, the amount of water added to the mix need to be adjusted according to the moisture

content value.

7

2.3.1.1.2 Moister content in concrete

Water is added to the concrete during batching to allow hydration of the cement and provide

the workability required to place and finish the concrete. Some water will be lost through

bleeding and evaporation, and some will be consumed by the hydration process. A small

quantity of water will remain following hydration of the cement either in the minute spaces

(capillary pores) within the concrete, or within the hydration products themselves (gel pores).

For low water-cement ratios, all the water in the mix may be consumed during hydration,

thus avoiding the necessity for the concrete to dry prior to the application of finishes.

In order to determine the correct amount of water as part of the design process, the Portland

Cement Association (PCA) states the following: “Mixture proportioning refers to the process

of determining the quantities of concrete ingredients, using local materials, to achieve the

specified characteristics of the concrete. A properly proportioned concrete mix should

possess these qualities:

1. Acceptable workability of the freshly mixed concrete

2. Durability, strength, and uniform appearance of the hardened concrete

3. Economy”

Parameters of the concrete affected by the addition of water to a load of concrete in excess of

the design water/cement, the following performance characteristics will likely be negatively

affected:

•Compressive Strength

The compressive strength of a concrete mixture is reduced when additional water is added.

•Resistance to cycles of freezing and thawing

•Resistance to damage from Sulfates in soil and water

•Permeability – and its associated impact to strength and various durability characteristics

•Minimizing potential for corrosion of reinforcing steel

2.3.1.2 Density and specific gravity

Density (D): weight per unit volume (excluding the pores inside a single aggregate)

Bulk density: the volume includes the pores inside a single fine aggregate.

Specific gravity (SG): mass of a given substance divided by unit mass of an equal volume of

water (it is the density ratio of a substance to water). Depending on the definition of volume,

the specific gravity can be divided into absolute specific gravity (ASG) and bulk specific

gravity (BSG). In practice, the bulk specific gravity value is the realistic one to use since the

effective volume that fine aggregate occupies in concrete includes its internal pores. The bulk

specific gravity of most rocks is in the range of 2.5 to 2.8.

2.3.1.3 Size distribution

The particle size distribution of fine aggregates is called grading. Sand particles range in

diameter from 0.0625 mm (or 1⁄16 mm) to 2 mm. An individual particle in this range size is

termed a sand grain. Sand grains are between gravel (with particles ranging from 2 mm up to

64 mm) and silt (particles smaller than 0.0625 mm down to 0.004 mm). The size specification

between sand and gravel has remained constant for more than a century, but particle

diameters as small as 0.02 mm was considered sand under the Albert Atterberg standard in

8

use during the early 20th century. A 1953 engineering standard published by the American

Association of State Highway and Transportation Officials set the minimum sand size at

0.074 mm. Sand feels gritty when rubbed between the fingers (silt, by comparison, feels like

flour).

To determine distribution of fine aggregate sieve analysis is done. Sieves, square mesh with

woven wire (brass or stainless steel). A full set of sieves shall include the following:

NO.1O-2mm

No. 18-1 mm

No. 35 - 500 micron

No. 60 - 250 micron

No. 100 - 149 micron

No. 140 - 105 micron

No. 270 - 53 micron

Plate 1: Arrangement of different size of sieves

The grading determines the paste requirement for a workable concrete since the amount of

void in aggregate are filled with same amount of cement paste in a concrete mixture. To

obtain a grading for fine aggregate, sieve analysis has to be conducted.

9

There are five different kinds of size distributions, dense graded, gap-graded, uniformly

graded, well graded and open graded. Dense and well-graded fine aggregates are desirable for

making concrete, as the space between larger particles is effectively filled by smaller particles

to produce a well-packed structure. Gap-grading is a kind of grading which lacks one or more

intermediate size. Gap-graded fine aggregates can make good concrete when the required

workability is relatively low. For the uniform grading, only a few sizes dominate the bulk

material. The open graded contains too much small particles and easy to be disturbed by a

hole.

2.3.1.4 Fineness modulus

To characterize the overall coarseness or fineness of fine aggregate, a concept of fineness

modulus is developed. To calculate the fineness modulus, the sum of the cumulative

percentages retained on a definitely specified set of sieves need to be determined, and the

result is then divided by 100.

The Fineness Modulus for fine aggregates should lie between 2.3 and 3.1. A small number

indicates a fine grading; whereas a large number indicates a coarse material. Fineness

modulus can be used to check the constancy of grading when relatively small change is

expected; but it should not be used to compare the grading of fine aggregates from two

different sources.

2.3.1.5 Shape and texture of aggregate

Fine aggregate shape and surface texture influence the properties of freshly mixed concrete

more than the properties of hardened concrete. Rough-textured, angular, and elongated

particles require more water to produce workable concrete than smooth, rounded compact

fine aggregate. Consequently, the cement content must also be increased to maintain the

Figure 1: particle size distribution graph Plate 2: particle size distribution graph

10

water-cement ratio. However, with rough fine aggregates, there is better mechanical bond in

the hardened concrete, so strength is higher (if concrete with the same w/c ratio is compared).

Hence, when smooth fine aggregates are replaced with rough fine aggregates, concrete of

similar flow properties and strength can be produced by adding a little bit more water.

Plate 3: shape and texture of aggregate (2)

2.3.2 UTILIZATION APPLICATIONS

Fine aggregates are used in various industries in different ways

I. underlying material for foundations

II. construction of bituminous roads

III. water treatment plants

IV. production of concrete

V. dam constructions

VI. Constructing aggregate base before placing the hot-mix asphalt

VII. Production of motor

VIII. Base of road

IX. Railway works

X. Production of curb or brick

XI. Precast concrete production

XII. Molds used in foundries for casting metal are made of fine aggregate

XIII. It is glued to paper to make sandpaper

XIV. Wall art

XV. Paint texture

XVI. Beach nourishment: Governments move sand to beaches where tides, storms or

deliberate changes to the shoreline erode the original sand.

XVII. Landscaping: Sand makes small hills and slopes (for example, in golf courses).

11

2.4 RIVER SAND

2.4.1 PRODUCTION

River sand is derived from rocks of the earth’s crust. Their properties are governed first by

the chemical and physical properties of the parent rocks. Rocks undergo various processes of

alteration, including natural geothermal and/or weathering processes which occur over long

periods of geological time. Such processes may produce granular materials in the form of

natural gravels and sands that can be used in concrete with a minimum of further processing.

On the other hand, production of sand may require processes encompassing human related

activities in the form of rock breaking, crushing, and so on. These processes, which convert

the rock in a very short period of time into useful engineering materials, must be linked to the

nature of the parent rock and the required properties of the sand, in order to produce

acceptable materials.

Natural sand can be sourced from pits, river banks and beds, the seabed, gravelly or sandy

terraces, beaches and dunes, or other deposits that provide granular materials that can be

processed with minimal extra effort or cost. Sand and gravel, which are unconsolidated

sedimentary materials, are important sources of natural sand. The occurrence of high quality

natural sands and gravels within economic distance of major urban areas may be critical for

viable concrete construction in those areas. (1)

2.4.2 PROPERTIES OF RIVER SAND

Material obtained from river sources will depend on the rocks present in the river’s catchment

area, and how readily they break down and weather to be transported in the river. During

river transport, rock fragments will undergo further weathering, be slowly reduced in size,

and be shaped by processes of attrition. Consequently, most river aggregates are reasonably

well shaped, rounded, and smooth.

A feature of many rivers is erratic flow, and consequently different particle sizes tend to be

transported and deposited during different regimes of flow. This can lead to marked

stratification, making it necessary to blend or mix the materials to obtain consistency and

uniformity and improve the grading. On the other hand, rivers with consistent flow will sort

and deposit the material, with rapid velocities giving a deficiency of fine material and vice

versa. Thus it may be necessary to blend the materials with other sources to extend the

grading envelope. River aggregates will generally have lower water requirements in concrete

due to their superior shape and surface texture, but the water requirement may be increased

by poor grading and absorptive fines in some cases.

Beach deposits

Beach materials fall within the influence of waves and tidal action. Being transported, they

generally have reasonably smooth textures and good particle shapes, although in the larger

sizes above 5–10 mm, particles tend to be discoid rather than spherical. The major deficiency

of beach sands is their poor grading, resulting from the sorting action of waves. Frequently,

only one or two particle sizes are present, with shortage or absence of fine material.

Consequently these materials, particularly sands, need to be blended with other aggregates to

improve grading and provide adequate fines for cohesiveness of the concrete mix.

12

Beach sands are composed mainly of quartz grains, but varying amounts of shell fragments

may also be present. This seldom presents a problem since these fragments are normally

sound and non-fragile. Higher shell contents (in excess of say 30 per cent) may lead to

increased mix-water if the shell fragments are poorly shaped or partly hollow.

Beach sands may also contain salts, but if they are washed so that the chloride content is no

greater than 0.01 per cent by mass, there should be no problem with corrosion of steel

embedded in concrete made with the sand. (6)

2.5 QUARRY DUST

2.5.1 PRODUCTION

Quarry dust is produced from the full range of quarrying activities including:

Extraction - (overburden removal, drilling and blasting, loading and hauling).

Rock preparation- (such as pre-screening and primary crushing and screening).

Further processing- (secondary, screening and treatment).

Quarry dust comprises material less than (about) 6 mm generated from any of the above

activities. They may be used as specific products (for example, as fine aggregate below 4

mm) or within other aggregate products (for example, as part of the overall grading for a sub

base). Quarry dust (that is material less than 6 mm) are an essential part of many aggregate

products and are intentionally produced by quarrying activities in order to provide the

required product grindings. The amount of dust produced during blasting is estimated to be as

high as 20% (The University of Leeds, 2007c).

There are certain advantages of crushed sands manufactured under modern controlled

conditions that may not always be appreciated:

(a) Modern crushing techniques can produce particle shapes equivalent or even superior to pit

sources.

(b) Controlled conditions can produce consistently uniform grading that may not be the case

with natural deposits where grading vary depending on the stratum of deposit being exploited

at any given time.

(c) Crusher sands are less likely to be contaminated with clay minerals and organic

substances than are natural materials. For this reason, higher fines contents for crusher sands

are often allowed in specifications, although care should be exercised when the source is

certain shale or basic igneous rocks which may contain undesirable clays.

13

Plate 4: quarry dust production (7)

2.5.2 PROPERTIES OF QUARRY DUST

Different quarries, or activities within the same quarry, may generate a range of quarry dust

in relation to their particle size and composition. For instance, dusts produced from primary

screening may have higher or lower clay content than those produced through tertiary

crushing and screening. Quarry dust is composed of the same mineral substances as the soil

and solid rock from which they are derived, even though changes to their physical and

chemical characteristics may have occurred. Quarry dust by their nature, are usually inert or

non-hazardous. Disaggregation, mixing and moving to different locations, exposure to

atmospheric conditions and to surface or groundwater, as well as segregation and the increase

of surface area due to particle size reduction, may cause physical and chemical

transformations with detrimental effects to the environment (BGS, 2003).

Quarry dust is considered more a consistent materials in relation to their composition and

particle size, also over time (temporal variability), they are commonly inert or non-hazardous

which means that their impact to the environment and human health is very low, and they

could provide some degree of security to the end user in terms of stable material supply.

Commonly, the decision making criteria upon which the suitability of quarry dust is

determined, are based on technical specifications and standards or on characterization

procedures developed by end users, such as construction product manufacturers. Therefore, it

is end users that define whether quarry dusts comprise a valuable material.

14

Parameters such as rock type, extraction technique and processing route, affect the generation

of quarry dust as well as their end properties, (for example, composition, particle size and

shape).

Plate 5: Typical quarry dust

2.5.3 UTILIZATION APPLICATION

Various utilization prospects exist for quarry fines, which can broadly be classified into

unbound and bound applications. Both categories of end use may require some degree of

processing of the quarry fines to be undertaken in order to comply with technical

specifications. End applications may be of high or low value, or may require a small or a

large volume of quarry fines.

These uses include:

15

2.5.4 EFFECTS OF QUARRY DUST ON ENVIRONMENT

Environmental protection and social responsibility is of vital importance to the quarrying

sector to reduce any adverse consequences (for example, in health and safety) and costs

associated with the production of quarry dust (for example, storage, dealing with arising

transport, and handling).

The generation of quarry fines may cause adverse impacts on the environment (such as the

local air, land, water, flora and fauna) and human health, and the mitigation of potential

impacts is mandatory. Commonly, various dust control practices (conventional or alternative)

are employed to minimize the impact of dust generated by quarry activities (Petavratzi et al,

2005; Petavratzi, 2006; EIPPCB, 2006). Health issues and the protection of fauna and flora

are addressed through the management and protection of air quality.

The utilization of quarry dust is seen as a way to minimize the accumulation of unwanted

material and at the same time to maximize resource use and efficiency. (8)

2.5.5 OBSTACLES TO UTILIZATION

Quarry dusts can be suitable materials for a variety of end applications; however, currently

their utilization is not widespread to the level it would have been expected mainly due to

reasons related to the geographical position of quarries.

Very often quarries operate in remote location from potential end users and the cost of

material to them includes high transport costs, which discourages their use. There are

occasions where producers of aggregates are not aware of potential utilization routes for their

quarry fines in the local area, and these materials remain unused.

Another major obstacle to utilization is the limited knowledge of exact quantities of quarry

fines. The figures on quantities of fines produced, marketed and stockpiled should be

calculated in order to properly evaluate the quantities of quarry fines currently available, and

information that present the geographical distribution of quarry fines, should be compiled to

enable the identification of potential end markets.

Some of the barriers to utilization are related to the location of quarry fines, the limited

awareness of potential markets by aggregate producers, the limited knowledge about quarry

dusts arising and their characteristics, and the absence of fully developed fit-for-use

specifications for a wide range of end products.

Often quarry fines require some degree of processing before they can be used, which may

increase their cost and at the same time requires suitable infrastructure and equipment to

become readily available. (9)

2.6 DESIGN OF CONCRETE MIXES

This is the process of selecting the correct proportions of cement, fine and coarse aggregate,

water and sometimes admixtures to produce concrete having specified and desirable

properties i.e. workability, compressive strength, density and durability requirements by

means of specifying the minimum or maximum water/cement ratio.

16

2.6.1 PRINCIPLES OF DESIGN

Strength Margin

Due to variability of concrete strengths, the mix must be designed to have higher mean

strengths than the characteristic strength. The difference between the two is the Margin. The

margin is based on the variability of concrete strengths from previous production data

expressed as a standard deviation.

Workability

Two alternative methods were used to determine workability; Slump test which is more

appropriate for higher workability mixes and the compacting factor test which is particularly

appropriate for mixes which are applicable to mixes compacted by vibration.

Plate 6: Typical quarry dust

Table 1: slump, compaction and workability relationship

Degree of

workability

Slump

(mm)

Compaction

factor

Use for which concrete is suitable

Very low 0 – 25 0.78 Very dry mixes. eg road making

Low 25 – 50 0.85 Low workability mixes. E.g. foundation with

light reinforcement

Medium 50 – 100 0.92 Medium workability mixes.eg in normal

reinforcement manually compacted

High 100 – 175 0.95 High workability concrete. For section with

congested reinforcement, normally not suitable

for vibration

Free – water

The total water in a concrete mix consists of water absorbed by the aggregate to bring it to

saturated surface – dry condition and the free – water available for hydration of cement and

for the workability of the fresh concrete. The workability of fresh concrete depends on a large

extent on its free – water content. In practice, aggregates are often wet and they contain both

17

absorbed water and free surface water so that the water added to the mixer is less than the

free – water content. The strength of concrete is better related to the free – water/cement ratio

since on this basis the strength of concrete does not depend on the absorption characteristics

of the aggregates.

Water Requirement of a mix is the quantity of water (in liters per cubic meter (l/m3))

required to produce concrete of a desired slump, with the given aggregates and binder,

without use of admixtures.

Water Demand, or Standard Water Requirement (SWR) of a mix is the quantity of water (in

l/m3) required to produce concrete with a slump of 75 mm, using aggregates of a nominal

maximum size of 19mm and ordinary Portland cement at a w/c ratio of 0.6, and without the

use of admixtures (Grieve, 2001).

Types of aggregates

Two characteristics of aggregates particles that affect the properties of concrete are particle

shape and surface texture. Particle shape affects workability of the concrete and the surface

texture affects the bond between the cement matrix and the aggregates particles and thus the

strength of concrete. Two types of aggregates are considered for design on this basis;

Crushed and Uncrushed.

Aggregate grading

The design of mixes was based on specific grading curves of aggregates. The curves of fine

aggregates must comply with grading zones of BS 882.

Mix parameters

The approach to be adopted for specifying mix parameters was reference to the weights of

materials in a unit volume of fully compacted concrete. This approach required the

knowledge of expected density of fresh concrete which depends primarily on the relative

density of the aggregate and the water content of the mix. This method was result in the mix

being specified in terms of the weights in kilograms of different materials required to produce

1m3 of finished concrete.

2.6.2 STAGES IN MIX DESIGN

STAGE 1: Selection of Target Water/Cement (W/C) ratio

STAGE 2: Selection of free – water content.

STAGE 3: Determination of cement content

STAGE 4: Determination of total aggregate content

STAGE 5: Selection of fine and coarse aggregate content

STAGE 6: Mix proportioning

18

2.7 BATCHING OF CONCRETE MATERIALS

Following the mix design process, concrete materials (Cement, Fine and Coarse Aggregates)

should be prepared early enough before the concrete works begins. This allows the smooth

running of the project. Batching of materials was done by weight. The advantage of weight

method is that bulking of aggregates (especially fine aggregates) does not affect the

proportioning of materials by weight unlike batching by volume method. Bulking of sand

results in a smaller weight of sand occupying a fixed volume of the measuring container thus

the resulting mix becomes deficient in sand and appears stony and the concrete may be prone

to segregation and honeycombing. Concrete yield may be reduced.

The batch weights of aggregates determined in the mix design process are based on saturated

surface – dry conditions. When working with dry aggregates, the following options may be

adopted to achieve saturated surface – dry conditions;

1. The batch weights of fine and coarse dry aggregates required for the trial mix were

calculated by multiplying the batch weights derived from mix design by 100/100+𝐴 ,where A

is the percentage by weight of the water needed to bring the aggregate to the saturated surface

– dry condition.

2. The dry aggregates are brought to a saturated surface – dry condition before mixing

process by addition of the required amount of water for absorption by the aggregate

according to BS 1881 – 125:1983.

3. Increasing the weight of mixing water to allow for the absorption of some mixing water by

the dry aggregate during mixing process.

Batching of concrete materials by weight may be expressed as follows;

Wt (C) + Wt (CA) + Wt (FA) + Wt (Air) = Wt (CC)

Where;

Wt (C) = Weight of cement.

Wt (CA) = Weight of coarse aggregate.

Wt (FA) = Weight of fine aggregate.

Wt (Air) = Weight of entrained air.

Wt (CC) = Weight of compacted concrete.

2.8 PROPERTIES OF CONCRETE.

2.8.1 PROPERTIES OF FRESH CONCRETE

2.8.1.1 Workability

Workability may be described as the consistence of a mix such that the concrete can be

transported, placed and finished sufficiently easily and without segregation. Workability may

also be specifically defined as the amount of useful work necessary to obtain full compaction

i.e. the work done to overcome the internal friction and the surface friction between the

individual particles in concrete and also between the concrete and the surface of the mould or

of the reinforcement.

19

The main factor affecting workability is the water content of the mix expressed in Kilograms

per cubic meter of concrete. If the water content and other mix proportions are fixed,

workability is governed by the maximum size of aggregate, shape and texture.

The free – water required to produce concrete of a specified slump depends upon the

characteristics of the aggregate. The grading of coarse aggregates, provided it complies with

the requirements of BS 882, has little effect on water requirement of a concrete mix. The

grading of fine aggregate has a considerable effect on the water requirement of the concrete.

Changing the grading of sand from a coarse one (e.g. 20% by weight passing the 600mm test

sieve) to a finer one (e.g. 90% by weight passing 600mm test sieve) can result in an increase

of water content of 25Kg/m3 in order to maintain the required workability of the concrete.

Such a change in water content would reduce considerably the compressive strength of the

concrete. The workability can be maintained by reducing the fines content.

2.8.1.2 SLUMP TEST

Slump test has been used extensively in site work to detect variations in the uniformity of mix

of given proportions. It is useful on the site as a check on the variations of materials being fed

to the mixer. An increase in slump may mean that the moisture content of aggregate has

increased or a change in grading of the aggregate, such as the deficiency of fine aggregate.

Too much or too low slump gives an immediate warning and enables the mixer operator to

remedy the situation.

The test is done according to BS 1881 – 102:1983 which describes the determination of

slump of cohesive concrete of medium to high workability. The slump test is sensitive to the

consistency of fresh concrete. The test is valid if it yields a true slump, this being a slump in

which the concrete remains substantially intact and symmetrical.

Plate 7: slump test

20

2.8.1.3 COMPACTING FACTOR TEST

This is the degree of compaction measured by the density ratio that is the ratio of density

actually achieved in the test to the density of the same concrete fully compacted.

The apparatus used consist of two hoppers, each in the shape of a frustum and one cylinder,

the three being above one another. The hoppers have hinged door at the bottom. All inside

surfaces are polished to reduce friction.

Compacting Factor =weight of partially compacted concrete ÷ weight of fully compacted

concrete

Plate 8: compaction factor apparatus

21

2.8.3 PROPERTIES OF CONCRETE.

2.8.2.1 COMPRESSIVE STRENGTH

Out of many test applied to the concrete, this is the utmost important which gives an idea

about all the characteristics of concrete. By this single test one can judge that whether

Concreting has been done properly or not. For cube test two types of specimens either cubes

of 15 cm X 15 cm X 15 cm or 10cm X 10 cm x 10 cm depending upon the size of aggregate

are used. For most of the works cubical moulds of size 15 cm x 15cm x 15 cm are commonly

used.

This concrete is poured in the mould and tempered properly so as not to have any voids. After

24 hours these moulds are removed and test specimens are put in water for curing. The top

surface of these specimens should be made even and smooth. This is done by putting cement

paste and spreading smoothly on whole area of specimen.

Plate 9: casted cubes ready to be remolded and cured

These specimens are tested by compression testing machine after 7 days curing or 28 days

curing. Load should be applied gradually at the rate of 140 kg/cm2 per minute till the

Specimen fails. Load at the failure divided by area of specimen gives the compressive

strength of concrete.

22

2.8.2.2 TENSILE TEST

Tensile strength is an important property of concrete because concrete structures are highly

vulnerable to tensile cracking due to various kinds of effects and applied loading itself.

However, tensile strength of concrete is very low in compared to its compressive strength.

Due to difficulty in applying uniaxial tension to a concrete specimen, the tensile strength of

the concrete is determined by indirect test methods: (1) Split Cylinder Test (2) Flexure Test.

It should be noted that both of these methods give the higher value of tensile strength than the

uniaxial tensile strength

2.8.2.2.1 Split-Cylinder Test

It is the standard test, to determine the tensile strength of concrete in an indirect way. A

standard test cylinder of concrete specimen (300 mm X 150mm diameter) is placed

horizontally between the loading surfaces of Compression Testing Machine.

The compression load is applied diametrically and uniformly along the length of cylinder

until the failure of the cylinder along the vertical diameter. To allow the uniform distribution

of this applied load and to reduce the magnitude of the high compressive stresses near the

points of application of this load, strips of plywood are placed between the specimen and

loading platens of the testing machine. Concrete cylinders split into two halves along this

vertical plane due to indirect tensile stress generated by Poisson’s effect.

Plate 10: cylinder in compression machine ready to be crushed

23

2.8.2.2.2 Flexure Test

After the Splitting tensile test another common test performed for determination of tensile

strength is the Flexure test.

The test could be performed in accordance with BS 1881: Part 118: 1983. A simple plain

concrete beam is loaded at one-third span points. Normal standard size of specimen is

150x150x750 mm. If the largest nominal size of the aggregate does not exceed 25mm, size of

150x150x500 mm may also be used. Span of the beam is three times its depth.

Plate 11: conducting of flexural test

The typical arrangement for the test is equal Loads are applied at the distance of one-third

from both of the beam supports. It induces equal reaction same as the loading at both of the

supports. Loading on beam is increased in such a manner that rate of increase in stress in the

bottom fibre lies within the range of 0.02 MPa & 0.10 MPa. The lower rate is for low

strength concrete and the higher rate is for high strength concrete.

From the loading configuration it is clear that at the middle one-third portion, in between two

loadings, the beam is subjected to pure bending. No shear force is induced within this portion.

It is this portion of beam where maximum pure bending moment of Pd/2 is induced

accompanied by zero shear force.

As loading increases, if fracture occurs within the middle one-third of the beam, the

maximum tensile stress reached called "modulus of rupture" fbt is computed from the

standard flexure formula.

24

2.9 STANDARDS FOR FINE AGGREGATE

GENERAL REQUIREMENTS

The fine aggregate shall consist of natural sand or, subject to approval, other inert materials

with similar characteristics, or combinations having hard, strong, durable particles.

Fine aggregate from different sources shall not be mixed or stored in the same pile nor used

alternately in the same class of construction or mix, without permission from the Engineer.

SPECIFIC REQUIREMENTS (2)

A. Deleterious Substances: The amount of deleterious substances shall not exceed the

following limits by dry weight:

Clay lumps........................................... 0.5%

Coal and lignite.................................... 0.3%

Shale and other materials having a specific gravity less than 1.95............. 1.0%

Other deleterious substances (such as alkali, mica, coated grains, soft and flaky

particles).............................. 1.0%

The maximum amount of all deleterious substances listed above shall not exceed 2.0 percent

by dry weight.

B. Soundness: When the fine aggregate is subjected to five cycles of the sodium sulfate

soundness test, the weighted loss shall not exceed ten percent by weight.

A satisfactory soundness record for deposits from which material has been used in concrete

for five years or more, may be considered as a substitute for performing the sodium sulfate

soundness test.

C. Organic Impurities: The fine aggregate shall be free from injurious amounts of organic

impurities. Aggregates subjected to the colorimetric test for organic impurities and producing

a color darker than the standard number 3 shall be rejected.

Should the aggregate show a darker color than samples originally approved for the work, it

shall not be used until tests have been made to determine whether the increased color is

indicative of an injurious amount of deleterious substances.

D. Alkali-Silica Reactivity (ASR) Requirements: When specified in the plans, the

following items shall apply.

Fine aggregates from sources that have not been tested shall be submitted to the Materials

and Surfacing Office for ASR testing 30 days prior to performing the concrete mix design.

ASR testing shall be performed in accordance with ASTM C1260, except that the gradation

of the material used for testing shall be as produced from the source

When a fine aggregate supplier changes locations within the pit, the fine aggregate from the

new location in the pit shall be resubmitted for testing.

When more than one source of fine aggregates is blended to meet the gradation

specifications, the expansion value of the blended sands will be used for determining

acceptability and type of cement required.

E. Grading: Fine aggregate shall be well graded from course to fine and shall conform to the

following grading requirements:

Passing 3/8 inch (9.50 mm) sieve............… 100%

Passing No. 4 (4.75 mm) sieve... .................. 95-100%

25

Passing No. 16 (1.18 mm) sieve.................... 45- 85%

Passing No. 50 (300 m) sieve....................... 10- 30%

Passing No. 100 (150 m) sieve...................... 2- 10%

F. Uniformity of Grading: The graduation requirements given above represent the extreme

limits which shall determine suitability for use from all sources of supply. The gradation from

any source shall be uniform and not subject to the extreme percentages of gradation specified

above. For the purpose of determining the degree of uniformity, a Fineness

Modulus (FM) shall be made upon representative samples from sources proposed for use.

Fine aggregate from any source shall maintain a fineness modulus within ±0.2 from the

design mix fineness modulus. If the fineness modulus falls outside this limit contact the

Concrete Engineer.

A new or adjusted design mix may be provided. The uniformity of grading requirements does

not apply to fine aggregate for Low slump Dense Concrete and Class M (I) concrete. (2)

26

CHAPTER 3 RESEARCH METHODOLOGY

The research methodology is aimed at giving the procedures of achieving objectives of the

project. The objectives and methods used to achieve them are as follows:

1. To investigate the compression and tensile strength of concrete made using quarry

dust as fine aggregate. Cubes and cylinders were prepared using 100% quarry dust as

fine aggregate. They were then crushed using compression machine and their results

compared with that of 100% river sand.

2. To investigate changes in strength of concrete as river sand is replaced with quarry

dust in different percentages. Several cubes and cylinders ware prepared using

different ratios of quarry dust and river sand as fine aggregate. They were crushed

and graphs drawled of the compression/tensile strengths on Y-axis and percentage

replacement on X-axis.

3. To observe the effect of quarry dust proportions on the workability of concrete. This

was done by conducting slump test and compaction factor of different ratios from

0% sand replacement to 100% sand replacement.

4. To test practical application of quarry dust concrete in construction of a hollow

fencing posts. Beams were prepared and crushed to determine the flexural strength

of concrete prepared with quarry dust as fine aggregate and results compared with

flexural strength of concrete prepared with river sand. A sample of hollow fencing

post was then prepared using 100% quarry dust as fine aggregate to show the

practical use of quarry dust.

5. To assess the cost implications of using quarry dust in concrete manufacture as

compared to river sand. Research was done on both the cost of quarry dust and river

sand. Production Cost of one meter cube of concrete was determined for different

percentage replacement of sand and results compared.

3.1 SAMPLE COLLECTION, PREPARATION AND ASSESSMENT

The cement, coarse and fine aggregates (sand & quarry dust) were obtained from the

Materials Laboratory in the Nairobi University. Coarse aggregate was crushed granitic stone.

Fine aggregate to be used was river-washed sand and quarry dust which was used to replace

river sand. Weight batching was done for different percentage replacement.

27

Grading

Objectives

i) To determine the particle size distribution of specified aggregates.

ii) To draw grading curves for the specified aggregates.

Apparatus

i) Balance accurate to ±0.5% of mass of test sample.

ii) Test sieves

iii) Tightly fitting pan and lid, for the sieves.

iv) Mechanism of shaking sieves.

v) Test data sheet for recording results.

vi) Brushes

Sieve sizes:

Coarse aggregates: 40mm, 30mm, 25.4mm, 20mm, 15mm, 10mm and 5mm.

Fine aggregates: 10mm, 4.75mm, 2.38mm, 1.2mm, 0.42mm, 0.3mm, 0.074mm and 0.15mm.

Procedure

1. Test sieves were arranged from top to bottom in order of decreasing aperture sizes

with pan and lid to form a sieving column.

2. The aggregate sample was then poured into the sieving column and thoroughly

shaken, manually.

3. The sieves were removed one by one starting with the largest aperture sizes (top

most), and each sieve shaken manually ensuring that no material is lost. All the

material which passed each sieve was returned into the column before continuing with

the operation with that sieve.

4. The retained material on the sieve with the largest aperture size was weighed and its

weight recorded with its corresponding sieve size.

5. The same operation was carried out for successive sieves in the column and their

weights recorded.

6. The screened material that remained in the pan was weighed and its weight recorded.

Calculations

1. Calculate the mass retained and passing on each sieve as a percentage of the original

dry mass.

2. Calculate the cumulative percentage of the original dry mass passing each sieve down

to the smallest aperture sieve.

28

3.2 SLUMP TEST

Objective

To determine slump of fresh concrete mix.

Apparatus

A standard mould (frustum of a cone) complying with BS 1881 – 102: 1983.

A standard flat base plate preferably steel.

A standard tamping rod.

Standard graduated steel rule from 0 to 300mm at 5mm intervals.

A scoop approximately 100mm wide.

Procedure

1) The inside surfaces of the mould was cleaned and oiled to prevent adherence of fresh

concrete on the surfaces.

2) The mould was placed on the base plate and firmly held.

3) The cone was then be filled with fresh concrete in three layer with each layer compacted

with 25 strokes of the tamping rod.

4) After filling the mould, the top surface was struck off by means of rolling action of the

tamping rod.

5) Immediately after filling, the cone was slowly and carefully lifted.

6) Immediately after removal of the mould the slump of the unsupported concrete was

measured and recorded.

Table 2: Slump test for all ratios

sand replacement (%) Slump (mm)

0

25

50

75

100

3.3 COMPACTING FACTOR TEST

Introduction

This is the degree of compaction measured by the density ratio that is the ratio of density

actually achieved in the test to the density of the same concrete fully compacted. The

apparatus used consist of two hoppers, each in the shape of a frustum and one cylinder, the

three being above one another. The hoppers have hinged door at the bottom. All inside

surfaces were polished to reduce friction.

29

Objective

To determine the workability of concrete mix by compacting factor method

Apparatus

Compacting factor apparatus

Weighing balance

Standard rod

A scoop approximately 100mm wide

A trowel or a float

Procedure

1. The inside surfaces of the hoppers and the cylinder were cleaned, dried and oiled to

reduce friction between the hopper surfaces and the concrete.

2. The upper hopper was then filled with concrete mix.

3. The door of the hopper was released so that the concrete fell on to the lower hopper.

4. The door of the lower hopper was released so that the concrete fell on to the cylinder.

Excess concrete was then cut by a trowel or a float. Concrete adhering to the cylinder

outside surfaces was removed.

5. The weight of the concrete in the cylinder was weighed. This gave the weight of the

partially compacted concrete.

6. Using the same cylinder, the concrete was re - filled in three layers, each layer

vibrated to achieve full compaction. The concrete was then weighed. This gave the

weight of fully compacted concrete.

Table 3: Compaction factor of different ratios

sand replacement (%) Partially

compacted (Kg)

Fully compacted (Kg) Compaction factor

0

25

50

75

100

Calculations

Compacting Factor =weight of partially compacted concrete ÷ weight of fully compacted

concrete.

30

3.4 DETERMINATION OF COMPRESSIVE STRENGTH

(Cube test to BS en 12390 – 2:2000)

Apparatus

i) platform balance

ii) Iron moulds, 150mm cubes

iii) Steel trowel

iv) Vibrator

v) Spade

vi) Mixing trough

Procedure

1. The inside of the moulds’ surfaces were first cleaned and oiled in order to prevent

development of bond between concrete and the mould. The moulds were then

assembled and bolts and nuts tightened to prevent leakage of cement paste.

2. Using the specified mixes the weights of the materials was determined.

3. The materials were mixed in the concrete mixer to a uniform consistency.

4. The specimens are cast in iron moulds, 100mm cubes, conforming to the

specifications of BS 1881 – 3:1970. A poker vibrator was used to ensure sufficient

compaction without causing segregation of concrete.

5. The top of the concrete was leveled off using the vibrator and smoothed off using a

steel trowel.

6. The specimens were then left in the moulds undisturbed for 24 hours before taking

them out of mould.

Curing of cubes

Curing may be defined as the procedures used for promoting the hydration of cement, and

consists of a control of temperature and of the moisture movement from and into the

concrete. The objective of curing was to keep concrete as nearly saturated as possible, until

the originally water – filled space in the fresh cement paste is filled to the desired extent by

the products of hydration of cement. The temperature during curing also controls the rate of

progress of the reactions of hydration and consequently affects the development of strength

of concrete. The cubes were placed in a curing pond/tank at a temperature of 20 ± 20C for the

specified period of time.

Before placing cubes into a curing tank they were marked with a water proof marker. Details

to be marked on the cubes are mainly; type of mix, date of casting, duration for curing and

crushing day.

Compressive Test

After curing the cubes for 7 and 28 days, they were removed and wiped to remove surface

moisture in readiness for compression test. The cubes was then be placed with the cast faces

in contact with the platens of the testing machine that was the position of the cube when

tested should be at right angles to that as cast. The load was applied at a constant rate of stress

of approximately equal to 15 N/mm2 to failure. The readings on the dial gauge was recorded

for each cube.

31

Table 4: Summary of Average cube Crushing Strengths at 7 days

sand

replacement (%)

Compressive Strengths (N/mm2) Average

Compressive

Strength (N/mm2) Sample 1 Sample 2 Sample 3

0

25

50

75

100

Table 5: Summary of Average cube Crushing Strengths at 28 days

sand replacement

(%)

Compressive Strengths (N/mm2) Average

Compressive

Strength (N/mm2) Sample 1 Sample 2 Sample 3

0

25

50

75

100

3.5 INDIRECT TENSILE TEST ACCORDING TO BS1881-117:1983

Apparatus

(i) Cylindrical moulds (150mm diameter by 300mm height)

(ii) Compression Testing Machine

(iii) Weighing machine

(iv) Mixing Trough

(v) Spade

(vi) Trowel

(vii) Vibrator

32

Procedure

The appropriate proportions of water, cement, sand, quarry dust and coarse aggregate

according to the calculated mix design ware used to come up with different replacement

mixes.

The mixes were then placed in the moulds using the trowel.

Compaction was carried out using a vibrator.

After filling the moulds the top of the moulds were leveled and finishing done.

The moulds were left in a moist atmosphere for 24 hours.

Curing of cylinder

After 24 hours the specimens were removed from the moulds and stored in a curing sink for 7

and 28 days. The objective of curing was to keep concrete as nearly saturated as possible,

until the originally water – filled space in the fresh cement paste was filled to the desired

extent by the products of hydration of cement. The temperature during curing also controls

the rate of progress of the reactions of hydration and consequently affects the development of

strength of concrete. Before placing the cylinders in water they were marked.

Tensile Test

The specimens were removed from the curing sink after 7 and 28 days and subjected to

indirect tensile testing using the compression testing machine.

From the maximum applied load at failure the indirect tensile strength was calculated as

follows

б= 2F/п*l*d

б is the indirect tensile strength in N/mm².

F is the maximum applied load in N.

l is the length of cylinder in mm.

d is diameter in mm.

Table 6: Seven days tensile Strengths

sand replacement

(%)

Cylinder Crushing Strengths (KN) Average tensile

Strengths

(N/mm2) Sample 1 Sample 2 Sample 3

0

25

50

75

100

33

Table 7: Twenty eight tensile Strengths

sand replacement

(%)

Cylinder Crushing Strengths (KN) Average tensile

Strengths

(N/mm2) Sample 1 Sample 2 Sample 3

0

25

50

75

100

3.6 FLEXURAL STRENGTH TEST TO BS 1881:118 – 1983

Flexural testing was used to determine the flexure or bending properties of a material.

Sometimes referred to as a transverse beam test, it involves placing a sample between two

knife-edge points and initiating a load at the midpoint of the sample. Maximum stress and

strain were calculated on the incremental load applied.

Casting beams

Plain concrete beams were cast in moulds. The beam was square of 100 mm. The overall

length of the specimen was 5d. The ratio of d to the maximum particle size of aggregate was

not less than three. Compaction was done using a poker vibrator. After compacting the top

layer it was then smoothened level using a plasterer’s float and the mould wiped clean to

remove adhering concrete on its outer surfaces. The specimens were then stored for 24 hours

in an undisturbed place and then cured for 28 days.

Loading beams

1. Beam specimens were removed from the curing tank and placed in the testing

machine. The specimens were centered with the longitudinal axis of the beam at right

angles to the rollers.

2. A load was applied at a constant rate through one roller at the midpoint of the span

until the specimen failed. The load was not applied until all loading and supporting

rollers are resting evenly against the test specimen. The load was applied without

shock and increases continuously, at the selected constant rate ±10 %, until no greater

load was sustained.

34

Loading of test specimen (centre-point loading)

Plate 12: Arrangement of loading of test specimen (centre-point loading)

Key

1 Loading roller (capable of rotation and of being inclined)

2 Supporting roller

3 Supporting roller (capable of rotation and of being inclined)

Expression of results

The flexural strength is given by the equation:

Where

fcf is the flexural strength, in megapascals (Newton’s per square millimeter);

F is the maximum load, in Newton’s;

l is the distance between the supporting rollers, in millimeters;

d1, d2 are the lateral dimensions of the specimen, in millimeters.

35

Table 8: Flexural test results

sand replacement (%) d1 d2 l F

0%

0%

0%

100%

100%

100%

3.7 Preparation of hollow fencing post

Apparatus

(i) Weighing machine

(ii) Mixing Trough

(iii) Spade

(iv) Trowel

(v) Vibrator

(vi) 55mm diameter plastic pipe

Casting of post

Plain concrete hollow post was cast in mould prepared at the timber laboratory. The post was

square of 120 mm with a circular hollow diameter 55mm made using plastic pipe. The overall

height of the post was 2000mm. Compaction was done using a poker vibrator. After

compacting the top layer it was then smoothened level using a plasterer’s float and the mould

wiped clean to remove adhering concrete on its outer surfaces. The post was stored for 24

hours in an undisturbed place and then cured for 28 days.

36

Plate 13: 100% sand replacement hollow fencing post

37

CHAPTER 4.0 RESULTS, DATA ANALYSIS AND

DISCUSSION

4.1 Sieve analysis

Weight of coarse aggregate used was 6453.5 gms

Table 9: sieve analysis of coarse aggregate

SEIVE

SIZE(mm)

WEIGHT

RETAINED

(gms)

WEIGHT PASSING

(gms)

%PASSING

38.1 0 6453.50 100

20 1426 5027.5 77.90

15 1152.5 3875.0 60.04

10 2064.5 1810.5 28.05

5 707 1103.5 17.10

2.36 118 985.5 15.27

<2.36 985.5 0 0

Graph 1: sieve analysis of coarse aggregate

0

20

40

60

80

100

120

0 0.5 1 1.5 2

pe

rce

nta

ge p

assi

ng

sieve sizes (mm)

seive analysis of coarse aggregate

Series1

38

River sand

Table 10: sieve analysis of river sand

SEIVE SIZE(mm)

WEIGHT

RETAINED

(gms)

WEIGHT PASSING

(gms)

%PASSING

10 0 425.0 100.00

5 2.5 422.5 99.41

2.36 6.5 416.0 97.88

1.18 40 376.0 88.47

0.6 276.5 99.5 23.41

0.3 29.5 70.0 16.47

0.15 50 20.0 4.71

0.075 13.5 6.5 1.53

pan 6.5 0.00

Graph 2: river sand sieve analysis

Quarry sand

Weight of quarry dust used was 332 gms

0

20

40

60

80

100

120

-1.5 -1 -0.5 0 0.5 1 1.5

pe

rce

nta

ge p

assi

ng

log sieve size

sieve analysis of river sand

39

Table 11: sieve analysis of quarry dust

SEIVE SIZE(mm) WEIGHT

RETAINED(gms)

WEIGHT PASSING

(gms)

%PASSING

10 0 332.0 100.00

5 50.0 282.0 84.93

2.36 62.5 219.5 66.11

1.18 106 113.5 34.19

0.6 47.5 66.0 19.87

0.3 37.0 29.0 8.73

0.15 15.5 13.5 4.06

0.075 8.0 5.5 1.65

pan 5.5 0.00

Graph 3: quarry dust sieve analysis

Discussion

Sieve analysis was done using the standard test sieves conforming to BS 410:1976.

Fine aggregate should be well graded from course to fine and should conform to the

following grading requirements:

Passing 3/8 inch (9.50 mm) sieve............… 100%

Passing No. 4 (4.75 mm) sieve... .................. 95-100%

0

20

40

60

80

100

120

-1.5 -1 -0.5 0 0.5 1 1.5

pe

rce

nta

ge p

assi

ng

log sieve size

quarry dust sieve analysis

40

Passing No. 16 (1.18 mm) sieve.................... 45- 85%

Passing No. 50 (300 m) sieve....................... 10- 30%

Passing No. 100 (150 m) sieve...................... 2- 10%

The results obtained of fine aggregates (both river sand and quarry dust) were within grading

requirement. Quarry dust was found to contain more fine particles compared to river sand

which contained more coarse particles.

Coarse aggregates particles were well distributed as seen from graph 4.1 in data analysis.

Grading was used during concrete mix design in the determination of the proportion of fine

aggregates and of course aggregate content.

4.2 Workability

Table 12: batching ratio 1:1.5:3(cement: fine aggregate: coarse aggregate)

BATCHING FOR THE CUBES

sand replacement

(%)

Mass of

cement(Kg)

Mass of quarry

dust(Kg)

Mass of river

sand(Kg)

Mass of coarse

aggregate(Kg)

0 3.1 0 4.6 9.3

25 3.1 1.2 3.4 9.3

50 3.1 2.3 2.3 9.3

75 3.1 3.4 1.2 9.3

100 3.1 4.6 0 9.3

Table 13: compaction factor of different ratios

sand replacement (%) Partially

compacted(Kg)

Fully compacted (Kg) Compaction factor

0 8.7 10.7 0.81

25 9.2 11.0 0.83

50 9.3 11.1 0.84

75 9.5 11.5 0.83

100 9.6 11.7 0.82

41

The variation of workability was also measured in terms of compaction factor with constant

w/c ratio (0.5).The values were obtained from different mixes such as 0% quarry dust, 25%

quarry dust, 50% quarry dust), 75% quarry dust and 100% quarry dust were 0.81, 0.83, 0.84,

0.83 and 0.82 respectively.

As per the data above, concrete does not give adequate workability with the increase of

quarry dust as fine aggregate.

Table 14: slump test for the all ratios

sand replacement (%) Slump (mm)

0 31

25 22

50 15

75 10

100 6

The measured slump values of quarry dust with constant water/cement ratio i.e. w/c ratio

(0.5) are 31mm,22mm,15mm,10mm and 6mm for different mixes such as 0% quarry dust,

25% quarry dust, 50% quarry dust,75% quarry dust and 100% quarry dust respectively. It

was observed that the slump value decreases with increase in percentage replacement of sand

with quarry dust for the same w/c ratio. It clear that quarry dust requires more w/c ratio than

river sand hence concrete does not give adequate workability with increase of quarry dust. It

can be due to the extra fineness of quarry dust

Increased fineness require greater amount of water for the mix ingredients to get closer

packing, results in decreased workability of the mix.

42

4.3 Compressive strength

Table 15: Summary of Average cube Crushing Strengths at 7 days

sand replacement

(%)

Compressive Strengths (N/mm2) Average

Compressive

Strength

(N/mm2)

Sample 1 Sample 2 Sample 3

0 16.5 16.5 16.8 16.73

25 16.7 16.8 16.6 17.1

50 16.9 17.0 16.8 16.9

75 16.9 17.3 17.1 16.7

100 16.6 16.9 16.7 16.6

Graph 4: seven days compressive strength

16.5

16.6

16.7

16.8

16.9

17

17.1

17.2

0 50 100 150

com

pre

ssiv

e s

tre

ngt

h

percentage replacement

compressive strength vs % replacement

compressive strength vs% replacement

43

Table 16: Summary of Average cube Crushing Strengths at 28 days

sand

replacement (%)

Compressive Strengths (N/mm2) Average

Compressive

Strength

(N/mm2)

Sample 1 Sample 2 Sample 3

0 22.6 22.8 22.4 22.83

25 23.1 22.8 22.8 24.9

50 24.2 24.3 23.8 24.1

75 25.0 24.8 24.9 22.9

100 23.1 22.7 22.7 22.6

Graph 5: twenty eight days compressive strength

Discussion

The results show that there is an increase in the compressive strength of the concrete with the

increment of quarry dust up to about 25% replacement then strength begins to reduce up to

100% replacement both for 7 and 28 days strength. At 75% replacement compressive strength

is almost equal to 0% replacement. The increase in strength on replacement is because quarry

fines act as filler hence fewer void while reduce in strength in 100% quarry dust is as result of

fewer larger particles as compared with sand hence poor workability.

22

22.5

23

23.5

24

24.5

25

25.5

0 20 40 60 80 100 120

com

pre

ssiv

e s

tre

ngt

h

percentage replacement

compressive strength vs % replacement 28 day

compressive strength vs %replacement 28 day

44

The strength of 0% replacement was higher than that of 100% replacement but with little

strength hence quarry dust is fit to be used as sand replacement material.

When results of 7 day strength was compared with 28 day strength it was found to range from

0.68 to0.73 which was within expected result of about or above 67%.

4.4 Tensile strength

Table 17: batching ratio 1:1.5:3(cement: fine aggregate: coarse aggregate)

BATCHING OF THE CYLINDERS

sand replacement

(%)

Mass of

cement(Kg)

Mass of quarry

dust(Kg)

Mass of river

sand(Kg)

Mass of coarse

aggregate(Kg)

0 14.5 0 21.8 43.6

25 14.5 5.4 16.4 43.6

50 14.5 10.9 10.9 43.6

75 14.5 16.4 5.4 43.6

100 14.5 21.8 0 43.6

Table 18: seven days’ tensile Strengths

sand replacement

(%)

cylinder Crushing Strengths (KN) Average tensile

Strengths

(N/mm2) Sample 1 Sample 2 Sample 3

0 125 124 126 1.77

25 130 126 127 1.81

50 121 125 125 1.75

75 115 120 119 1.67

100 110 110 118 1.59

Tensile strength = 2P/surface area

45

Graph 6: seven days tensile strength

Table 19: twenty eight day tensile strength

sand

replacement (%)

cylinder Crushing Strengths (KN) Average

cylinder

Crushing

Strengths

(N/mm2)

Sample 1 Sample 2 Sample 3

0 190 185 190 2.66

25 195 190 192 2.72

50 185 185 188 2.63

75 175 185 183 2.56

100 180 175 180 2.52

1.55

1.6

1.65

1.7

1.75

1.8

1.85

0 20 40 60 80 100 120

ten

sile

str

en

gth

percentage replacement

tensile strength vs % replacement

tensile strength vs %replacement 7 day

46

Graph 7: twenty eight day tensile strength

Discussion

The tensile test result also showed increase in strength as percentage replacement increased

up to 25% replacement then strength began to reduce up to 100% replacement. The increase

was not much as that of compressive strength and 50% was almost equal to 0% replacement.

In design of concrete structures, concrete is considered to have low tensile strength and steel

reinforcements are used hence tensile strength for all replacement is ok. The ratio of 7 day

tensile strength to 28 day tensile strength was 0.66 which is about the expected range 0.67 or

67%.

2.5

2.55

2.6

2.65

2.7

2.75

0 20 40 60 80 100 120

ten

sile

str

en

gth

percentage replacement

tensile strength vs % replacement

tensile strength of 28 day

47

4.5 Flexural strength

Table 20: 5 twenty eight day flexural strength of beams

Flexural test

sand replacement

(%)

d1(mm) d2(mm) l(mm) F(KN) fcf (N/mm2)

0% 100 100 300 12.57 5.66

25% 100 100 300 12.17 5.57

50% 100 100 300 12.37 5.48

75% 100 100 300 11.57 5.30

100% 100 100 300 11.77 5.21

Where

F is the maximum load, in Newton’s;

l is the distance between the supporting rollers, in millimeters;

d1, d2 are the lateral dimensions of the specimen, in millimeters.

Graph 8:twenty eight day flexural strength

5.15

5.2

5.25

5.3

5.35

5.4

5.45

5.5

5.55

5.6

5.65

5.7

0% 20% 40% 60% 80% 100% 120%

fle

xura

l str

en

gth

percentage replacement

flexural strength vs % replacement

flexural strength vs %replacement

48

Discussion

Flexural strength decreased as the percentage replacement increased from 0% replacement up

to 100% replacement. The flexural strength different between 0% sand replacement and 100

% sand replacement was not large (0.45N/mm2) hence was within same range. The strength

characteristic required in fencing post is flexural strength hence quarry dust as fine aggregate

can be used to prepare hollow fencing post.

4.6 Cost Benefit Analysis

In cost benefit analysis exercise the total cost of producing a specified quantity of concrete

was analyzed in order to ascertain whether it’s more economical to use quarry dust as better

replacement of sand in terms of its cost and benefits

Price of a ton of sand = KS. 1950

Price of a ton of Ballast = KS 1780

Price of 50kgs of cement = KS 800

Price of Quarry Dust = KS 1500

One meter cube of concrete was considered and the rates below;

1m3 multiplied with density of concrete 2400kg/m3 to get 2500kg of concrete.

Taking a mix ratio of 1:1.5:3 (cement: fine aggregate: coarse aggregate) the of each ratios is

436.4kg: 654.5kg: 1309.1kg

The weight of fine aggregate was considered during replacement of sand which is 654.5kg. A

summary of the cost analysis for this project is presented in the tables below;

Table 21: mass of different ratios

Percentage replacement Quarry dust (kg) River sand (kg)

0% 0 654.5

25% 163.6 490.9

50% 327.2 327.2

75% 490.9 163.6

100% 654.5 0

49

Table 22: Costs of different replacement

Percentage

replacement

Quarry dust (ksh) River sand (ksh) Total cost

0% 0 1276.28 1276.28

25% 245.40 957.26 1202.66

50% 490.80 638.04 1128.84

75% 736.35 319.02 1055.37

100% 981.75 0 981.75

Graph 9: Graph of total prices against the quarry

Discussion

The results were a decrease in cost with increase in percentage replacement of sand with

quarry dust. 100 % replacement of sand gave the lowest cost hence its economical to replace

sand with quarry dust in concrete production.

0

200

400

600

800

1000

1200

1400

0% 50% 100% 150%

cost

in k

sh

% replacement

cost comparison

cost comparison

50

4.7 General discussion

Generally increase in replacement of river sand with quarry dust resulted to increase in both

compression and tensile strength of concrete. But different rocks have different chemical

properties depending on their method of formation hence its necessary to carry out different

strength test whenever using quarry dust.

As the replacement of the sand with quarry dust increases the workability of the concrete is

decreasing due to the absorption of the water by the quarry dust hence water/cement ratio

should be increased with increase of quarry dust replacement to maintain slump required.

51

6. Conclusion and recommendation

6.1 Conclusion

The experimental data shows that the addition of quarry dust improves the strength properties

of concrete. Due to the high fines of quarry dust it provided to be very effective in assuring

very good cohesiveness of concrete. From the above study it is concluded that the quarry dust

may be used as a replacement material for fine aggregate up to 75% replacement.

Currently Quarry dust is used for different activities in the construction industry such as for

road construction and manufacture of building materials

From the laboratory study conducted as explained above following conclusions are drawn.

1. Non availability of river sand at reasonable cost as fine aggregate in cement concrete for

various reasons, search for alternative material stone crushed dust qualifies itself as a suitable

substitute for sand at lower cost.

2. Aggregates with higher surface area are requiring more water in the mixture to wet the

particle surfaces adequately and to maintain a specific workability. Obviously increasing in

water content in the mixture will adversely affect the quality of concrete.

3. The slump value decreases with increase in percentage replacement of sand with quarry

dust is due to flaky particles shape and higher percentage of fines. Concrete does not give

adequate workability with higher water/cement ratio and the concrete tends to segregate.

4 The compressive strength and tensile strength maximum increase was about 25%

replacement hence during construction of heavy weight structures it’s recommended to use

mixture of quarry dust and river sand rather than quarry dust or river sand alone.

5. Compression strength of 0% replacement had equal value to that of 75% replacement

hence for medium weight structures it’s recommended to use the 75% replacement mixture.

6. It was observed in compaction test that the density of concrete increases with increase in

percentage of dust content. As expected the compressive strength increases with increase in

density of concrete.

7. Although there is decrease in flexural strength with increase of sand replacement the

difference is small hence quarry dust can be used in structures in which design depend mainly

on flexural strength (e.g. fencing post).

In order to achieve Kenya’s vision 2030 cheaper construction materials and conservation of

environment are necessary. Quarry dust is cheaper than river sand and its use will reduce

environmental degradation in various ways:

Reduction of overdependence on natural sources of river sand

52

Quarry fines products can be put into more use as fine aggregates in concrete, other

than dumping and land filling.

6.2 Recommendation

From the test results and analysis above, 50% to 80% replacement of river sand with quarry

dust would be recommend. However for light weight structures such as fencing post, culverts,

one story buildings I would recommend 100% replacement.

It is necessary for trial test with the proposed quarry dust to be carried out in order to achieve

the most suitable water/cement ratio and mix proportions to suit compression strength, tensile

strength and flexural strength required.

One should investigate the chemical composition of rock from which quarry dust is extracted

to prevent any chemical reaction which would lower the strength of concrete.

Further research should be carried out to determine the long term strengths of quarry dust

concrete and also the strengths of quarry dust in reinforced concrete.

53

REFERENCES 1. (Aggregates in Concrete by Mark Alexander & Sidney Mindess. ‘Modern Concrete

Technology 13’)

2. (Materials For Civil and Construction Engineers By Michael S. Mamlouk & John P.

Zaniewski. Third Edition)

3. (Ref: International Journal of Advanced Engineering Research and Studies)

4. (Orchard, D.F. (1976) Concrete Technology, Volume 3, Properties and Testing of

Aggregates, London: Applied Science.)

5. (Brown, B.V. (1993) ‘Aggregates: The greater part of concrete’, in R.K. Dhir and M.R.

Jones (eds), Concrete 2000, London: E&FN Spon.)

6. (M.S. Shetty, Concrete Technology Theory and Practice, 5thedition, S.Chand & Co. Ltd.,

New Delhi)

7. (Md.Safiuddin, S.N.Raman and M.F.M. Zain, Utilization of Quarry waste fine Aggregate

inconcretemixures, 2007 Journal of Applied sciences research 3(3) : 202-208)

8. (M.S.Jaafar, W.A.Thanoon, M.R.A.Kadir and D.N.Trikha, Strength and Durability

characteristics of high strength autoclaved stone dust concrete, The Indian concrete journal,

December 2002 , pp771-774. )

9. (Strength and durability properties of concrete containing quarry dust as fine aggregate,

R.Ilangovana, N.Mahendrana and K.Nagamanib, Pg.No. 20 to 26, ARPN Journal of

Engineering and Applied Science, Vol.3,No.5, October 2008. )

54

Appendix

THE MIX DESIGN PROCESS (Based on the procedure given by the Department of Environment – Transport and Road Research Laboratory,

London)

Figure A-1(fig 4): Relationship between compressive strength and Free – water/cement ratio

Figure A-2(fig 3): Relationship between standard deviation and characteristic strength

The margin; Equation C1

The margin may be derived from the calculation below:

𝑀=𝑘×𝑠 ……………………………………..…C1

where M= the margin.

55

k= a value appropriate to the ‘percentage defectives’ permitted below the characteristic strength.

s= the standard deviation

The target mean strength; Equation C2

𝑓𝑚=𝑓𝑐+𝑀 …………………………………..C2

Where 𝑓𝑚 = the target mean strength

𝑓𝑐 = the specified characteristic strength

𝑀 = the margin

Cement content; Equation C3

Cement content = free – water content

water/cement ratio ………………………………..…….C3

Total Aggregate content; Equation C4

Total aggregate content = 𝐷−𝑊𝐶−𝑊𝐹𝑊 …………….………………………..C4

Where 𝐷 = the wet density of concrete (Kg/m3)

𝑊𝐶 = cement content (kg/m3)

𝑊𝐹𝑊 = free – water content (kg/m3)

Fine and coarse aggregates contents; Equation C5 & C6

Fine aggregate content = total aggregate content × proportion of fines …….…….C5

Coarse aggregate content = total aggregate content – fine aggregate content …….…….C6

56

Figure A-3 (fig 5 & 6): Charts used in mix design

57

58

Chapter 3

Properties and characterization of aggregates If concrete science and technology are to keep pace with developments in other fields of engineering, it is essential that we make the most effective use of concrete materials. It is necessary to move beyond simply knowing the properties of the aggregates to an understanding and application of the effects of their properties on concrete in its various forms. The link between aggregate properties and performance in concrete is not yet entirely understood in many respects. Aggregate properties have profound influences on concrete properties, and these influences need to be understood and appreciated. Concrete aggregates are required to meet minimum standards of cleanliness, strength, and durability, and to be substantially free of deleterious substances. Materials that are soft, very flaky, too porous, or that can react detrimentally in concrete should be excluded. For this reason, thorough testing and examination, including petrographic examination, should be carried out before new or untried sources of aggregate are used. Aggregates for concrete are characterized by using standard tests. Absorption and moisture state Aggregates that are porous can absorb water. Absorption is thus governed by porosity. For the pores of an aggregate particle to fill with water, the pores must be interconnected and open to the surface so that water from the exterior can penetrate the solid. This is not always the case, and what is measured is usually an ‘apparent porosity’ which does not account for the impermeable pores. This is not normally a problem, except that the density or strength of the aggregate may be affected. Absorption is measured in the same type of test as that for porosity, by allowing oven-dry aggregates to absorb water while being submerged and then measuring their mass in a saturated-surface-dry (SSD) condition. Absorption is expressed as the ratio of the increase in mass of an oven-dried sample after saturation to the mass of the saturated-surface-dry sample, in per cent. Water absorption of less than 1 per cent will have little practical effect on concrete properties such as shrinkage and creep. Aggregates with absorptions much higher than 2–3 per cent should be treated as suspect and checked for their influence on concrete performance, for example whether they impart higher drying shrinkage to concrete. Absorption limits are rarely specified in standards, although project-specific specifications may if a suspect aggregate is likely to be used. Where a relationship exists between absorption and some other undesirable property such as poor frost resistance, water absorption limits may be specified for control and compliance purposes. Porous aggregates may adversely affect the resistance of concrete to freeze–thaw conditions. .

(aggregate in concrete by Mark Alexander and Sidney Mindess page 80)