pumice as sand

Chapter 1

INTRODUCTION

1.1 BACKGROUND OF STUDY

Concrete, as a basic necessity for project constructions in the Bicol Region, raised ideas

about altering its compositions and mixtures that involved new kinds of aggregates may it be fine

or coarse. As part of every concrete, mortar always played a major role. If one considers its uses

like for plastering, tiles and hollow blocks grouting, and its role in the concrete cement as a

binder of coarse aggregates, truly it should be highly regarded.

Mortar as part of concrete cement has a direct effect to the concrete’s service load

capacity. Good mortar in concrete obviously improves concrete allowing it to carry higher

service loads. Mortar, also used as plaster and grout, on the other hand has direct effect on slabs

and beams due to its own weight which increases the service load carried by the structural

members, thus causing a new field for research regarding mortars with lesser weight.

There are so many innovations in making the concrete lighter in order to reduce the loads

which would result to the decrease on the dimensions of the beams, columns, footings, and other

load bearing members. Lightweight concrete could be manufactured using lightweight

aggregates both fine and coarse or normal aggregates and lightweight fine aggregates.

For past studies in the Philippines regarding lightweight concrete, researchers worked

very hard to attain the required compressive strength of 17 MPa or 2500 psi for residential

buildings using both fine and coarse lightweight aggregates, but they did not succeed. These

researchers found out that there were so many factors to be considered. The specific gravity of an

1

aggregate plays a big role in the computation of the design mix. Since, the lightweight floats on

water, for now, the past researchers had not found a way to determine the specific gravity of the

aggregates due to the lack of equipment in their locations.

In order to simplify the research due to its complications, the researchers decided to focus

on determining the compressive strength of mortar itself using lightweight fine aggregates. The

proponents used pumice as their lightweight aggregate since it is locally available and abundant.

Bicol Region as part of a tropical country, the Republic of the Philippines, is rich in

natural resources. These resources include coarse and fine aggregates that can be used in

construction. In addition to this, pumice, a lightweight rock, is available in Casiguran, Sorsogon.

In this comparative study between ordinary and lightweight fine aggregates used in mortar

cement, the researchers used this pumice, which were crushed to make fine aggregates.

2

1.2 STATEMENT OF THE PROBLEM

This study aims to evaluate the differences and similarities of ordinary sand mortar

cement and pulverized pumice mortar cement.

1. Which among the two mixes posses higher strength capacity?

2. How much lighter is the pulverized pumice mortar cement compared to the ordinary

mortar cement?

3. What effect do lightweight aggregates when combined with ordinary cement have to

the mortar cement?

4. What would be the factors that could affect the compressive strength of the

lightweight mortar?

1.3 SIGNIFICANCE OF STUDY

This study shall benefit the following:

To Teachers, Students and Civil Engineers, this research will generate other innovative

ideas for the use of lightweight in construction specially mortar.

To End Users, this will benefit them through economical purposes since lightweight

mortar cement reduces the dead load carried by structural members, which then allows structural

designers to reduce the sizes of load bearing members.

To Future Researchers, this research will serve as their reference and basis for their own

study.

3

1.4 GENERAL OBJECTIVE

The main objective of this study was to evaluate and compare the strength and weight of

the mortar using ordinary sand and pulverized lightweight rocks. Furthermore, it also

endeavoured to determine the effect of introducing crushed pumice to sand mortar, which means

the combination of lightweight fine aggregate and ordinary sand.

1.5 SPECIFIC OBJECTIVE

The specific objective of this study was to closely compare the strength and weight

difference between the lightweight-mixed mortar, ordinary-mixed mortar, and combined-mixed

mortar, thus allowing the research to show results that can be used in further studies and actual

constructions.

4

1.6 ASSUMPTION

This comparative research analysis assumed that lightweight mortar mixes were

significantly lighter than ordinary mortar mixes. Thus, their strength capacities were relatively at

par and either can be used for construction.

1.7 SCOPE AND LIMITATION

Scope

This comparative research analysis was intended to qualitatively compare ordinary

mortar mixes and lightweight mortar mixes. In this research, the mortar mixes’ strength and

weight were closely evaluated. In turn, this research may be used as a basis for consideration of

lightweight mortar mixes in actual constructions.

Limitations

This research was limited only to the attainment of the highest possible strength of mortar

cement mix using crushed pumice, Portland cement and Albay sand.

The researchers did not use any mixing equipment due to the unavailability of such; thus,

what the proponents did was to mix the mortar manually, so there might be irregularities in some

aspect of the design mix such as the water-cement ratio that also affects the workability of the

mix aside from its compressive strength.

The researchers used 1:1 ratio, 1:2 ratio, 1:3 ratio and 1:4 ratio in designing the mix

which is basically not present in any existing codes. This cement-fine aggregate ratio was based

on the observations and findings on the actual field conditions or construction sites.

5

1.8 DEFINITION OF TERMS

The following terms were defined according to its context in engineering:

Absorption. This refers to the ability of a material to hold water within itself

Cement Mortar . This is an intimate mixture of cement and sand mixed with sufficient water to

produce a plastic mass. The amount of water varies according to the proportion and condition of

the sand, and had best be determined independently in each case. Sand is used both for the sake

of economy and to avoid cracks due to shrinkage of cement in setting.

Cementitious. This relates to a chemical precipitate, especially of carbonates, having the

characteristics of cement.

Compressive strength. It is the capacity of a material to withstand axially directed pushing

forces.

Curing. It pertains to a procedure for insuring the hydration of the Portland cement in newly-

placed concrete. It generally implies control of moisture loss and sometimes of temperature.

Dead load. This refers to the intrinsic invariable weight of a structure, such as a bridge. It may

also include any permanent loads attached to the structure also called dead weight.

6

Pumice . This is also called pumice stone, a light porous acid volcanic rock having the

composition of rhyolite, used for scouring and, in powdered form, as an abrasive and polish.

Pumice Cement Mortar. This is a mixture of crushed pumice as sand substitute and cement

mixed with sufficient amount of water.

Sieve Analysis (or gradation test). This is a practice or procedure used to assess the particle

size distribution (also called gradation) of a granular material.

Specific Gravity. This refers to the ratio of cement’s density to the density of some standard

material, such as water at a specified temperature, for example, 60°F (15°C), or (for gases) air at

standard conditions of temperature and pressure. Specific gravity is a convenient concept

because it is usually easier to measure than density, and its value is the same in all systems of

units.

7

Chapter 2

REVIEW OF RELATED LITERATURE AND STUDIES

A. RELATED LITERATURE

The use of pumice has been known to the world centuries ago. One application of pumice

was during the ancient Rome. Pumice was used to build thermal baths and temples, like

Pantheon of Rome. Vitruvio’s compendium of architecture, dated from 1st B.C., is one of the

earliest references regarding the special properties of pumice. Vitruvio describes that pumice is

lighter than water.

Other special properties of pumice are thermal insulation, sound insulation, and

resistance to freezing, resistance to fire, water absorbency and apparent density. Pumice has

reduced thermal conductivity than that of normal concrete. Also, pumice is a good sound

insulator due to its high absorbency of sound. Pumice, also, has higher water absorbency than

that of ordinary aggregates used in construction.

Resistance to freezing is one of the special properties of pumice. An experiment was

conducted to prove that pumice samples are resistant to intense cold. Samples submerged in

water for 48 hours, placed in a freezer at 100C for 9 hours and immersed again in water at 350C

for 15 hours (and submitted to this cycle 20 times) showed no visible signs of damage,

deterioration or breakdown. Also pumice is resistant to fire. When a 60 mm thick wall is exposed

to flame with temperature of 12000C, the temperature of the opposite side will not exceed

1250C. Many chimneys could be made of pumice concrete or blocks. (APEX GULF, 2003)

8

Building with Pumice

Pumice is a very porous form of vitrified volcanic rock, usually of very light colon.

Pumice floats on water. In other words, pumice is very light. It has roughly the consistency of a

mixture of gravel and sand, with light, porous individual granules that normally either float on

water or sink slowly.

Pumice has the following chemical composition:

Table 1. Chemical Compositon of Pumice

Silica SiO2 approx. 55%

Alumina Al2O3 approx. 22%

Alkalies K2O+Na2O approx. 12%

Ferric Oxide Fe2O3 approx. 3%Lime CaO approx. 2%Magnesia MgO approx. 1%

Titania TiO2 approx. 0.5%

Pumice originates during volcanic eruptions when molten endogenous rock is mixed with

gases before being spewed out. The light, spongy particles are hurled up and carried off by the

wind. As they cool and fall back to earth, the particles accumulate to form pumice rock or

boulders. Pumice is deposited with a layer thickness of 50 to 300 cm.

Pumice is very light, inexpensive, refractory, resistant to pests, sound absorbent, and heat

insulating. Also, pumice is easy to work with since it can be cut or sliced by a saw. Aside from

its positive properties, it also has down sides. The lower compressive strength of pumice

concrete, as compared to concrete containing other, heavier aggregates, and the tendency of its

edges and corners to break off more easily than those of heavy concrete. From this down sides,

9

the pumice building material should not be used for foundations, components subjected to heavy

traffic and high loads.

Pumice can build buildings such as single-storey homes, apartment buildings up to four

storeys, workshops, storehouses and schools. These buildings could be made using pumice-

concrete solid bricks, hollow blocks, planks, and in-situ pumice-concrete.

Pumice lightweight concrete has been used in many countries. The tallest building in

Istanbul, Turkey, the Sapphire tower, was built using lightweight concrete. Over a million cubic

yards of lightweight Pumice concrete had been placed successfully in Istanbul Sapphire high-rise

construction that was vacuum saturated by the Lightweight Concrete vacuum processing system.

In addition, one of the museums in Istanbul, built by the Roman Empire in 537, used pumice.

(Hannah Schreckenbach, 1990)

10

B. RELATED STUDIES

Pumice stone has been used for centuries in the world. Pumice aggregate can be found in

many places around the world where volcanoes are. Although it has been used successfully in

many countries finding new and improved ways to build with pumice is becoming widespread.

Due to its toughness and durability, pumice is a well known lightweight concrete aggregate for

over 2000 years. Pumice aggregates combined with Portland cement and water produce a

lightweight thermal and sound insulating, fire-resistant lightweight concrete for roof decks,

lightweight floor fills, insulating structural floor decks, curtain wall system, either prefabricated

or in situ, pumice aggregate masonry blocks and a variety of other permanent insulating

applications.

Experimental test results showed the pumice aggregate lightweight concrete up to 25:1

(Aggregate-Cement) ratios has sufficient strength and adequate density to be accepted as load-

bearing block applications. Further increasing this ratio can be accepted as non-load bearing

infill blocks for insulation purposes for it has sufficient strength, adequate density and the

thermal conductivity. Decreasing the aggregate ratio increases strength quality of pumice

aggregate lightweight concrete while increasing the aggregate ratio increases the thermal

insulation property. Basically, non-structural lightweight concrete can be produced by the use of

pumice aggregates without using any admixtures.

Lightweight concrete characteristics depend on the aggregate water content prior to

mixing. Excessive water content causes lack of adherence between the aggregate and mortar,

while low aggregate water content causes the aggregate to soak up part of the mortar water, thus

causing a cement sub-hydration and consequent reduction of the concrete shape alteration

11

capacity. Both cases result in lower resistance characteristics than when the aggregates are

moderately soaked just prior to concrete preparation. (GUNDUZ L., 2008)

Pumice has many desirable properties when used as lightweight aggregate in concrete.

One of the properties is the excellent compressive strength to weight ratio (up to 27MPa for 1750

kg/m3 concrete). Lightweight concrete has an excellent sound absorption for a given wall

thickness and wall mass. It has low thermal conductivity and non-flammable, giving increased

fire resistance ratings to masonry walls. Finally, it can totally replace conventional sands and

aggregates in masonry formulations with a combination of pumice sands and larger pumice

aggregates.

In addition to these benefits, pumice is also pure and non-toxic, so exposure to pumice

has no health implications, no special storage, but handling is required. It is environmentally

friendly, with low energy extraction or preparation, lower transport costs than higher density

aggregates, no degradation into soluble or volatile components with time. Pumice, when in fine

particle form, where the silicon and aluminum oxides in pumice react with lime and water to

form rock hard non porous material are also the basis for the curing of Portland cement, and were

used by the Romans in the construction of most of the ruins that still exist today. (STAR LTD.

PUMICE CORPORATION, 2008)

12

Sagales and Presentacion of Ateneo de Naga University titled their study “Design Mix of

Lightweight Concrete Containing Pumice Gravel, Albay Sand and Portland cement”. They

aimed to attain the highest possible compressive strength and to provide desirable concrete mix

proportions using pumice as coarse aggregate, Albay sand as fine aggregate, and Portland

cement. This study also aimed to gather information regarding the effect of the change in volume

of coarse aggregate into the lightweight concrete mixture. The product of the research would

serve as sample design mixtures in producing lightweight concrete using aggregates found here

in the Bicol region.

They found that pumice is a very weak material due to the results of their research which

showed that the compressive strength of pumice-crete was low since they only attained 1306.95

psi as the highest compressive strength.

Unlike normal weight concrete, using a greater volume of pumice as gravel would make

the pumice concrete to some extent weaker. This is mainly due to the weak compressive

capability of the pumice. The strength therefore of a lightweight concrete, in the case of pumice

concrete, comes from the strength of its mortar. But it does not mean that using very small

amounts of pumice is advisable. The test results showed that lesser pumice and higher cement

factors gave only a slight improvement in the concrete’s strength. Therefore it was not

economical to use high cement factors and low pumice contents. This was observed especially in

the case of the first design mixture where the curing period was only seven days, the amount of

pumice was somehow the largest among the specimens, and the cement factor was minimal but

still it showed a promising result. (Sagales and Presentation, 2010)

13

Another study from Ateneo de Naga University, College of Engineering, Bonavente and

Pacardo explored in their research “The Use of Waste Glass as a Substitute for Sand in

Construction”. Their research aimed to promote alternative methods in construction through the

use of waste glass as a substitute for sand in concrete mixes. It also aimed to provide a

concentrated source of information regarding the new innovations specific to other uses of glass–

particularly its applicability as an alternative aggregate material rather than its applicability as an

aesthetic aspects in construction.

If crushed pieces of glass were used partly in concrete mixtures – say 50% of fine

aggregate is composed of glass and the other 50% is composed of sand, it can be of use in

concrete mixtures. From their compressive test results, this type of mixture was much better than

that of crushed glass purely substituted to sand as fine aggregate. Therefore, it helped in the

attainment of a much higher compressive stress of concrete.

For mortar tests, the applicability of crushed glass passing at sieve no. 50 and below

appeared to be satisfactory. Based on the result of their conducted experiment, if crushed glass is

to be used as fine aggregate for cement mortars, the amount of crushed glass to be included in

the design mixture must not be greater than 75% of the whole mixture. This should be done in

order for the cement mortar using crushed glass as fine aggregate be classified as to what type of

cement mortar they belong. (Bonavente and Pacardo, 2010)

14

Chapter 3

CONCEPTUAL FRAMEWORK OF STUDY

LABORATORY MIXING

FINDINGS AND TABULATION OF RESULTS

EVALUATION OF DATA GATHERED

Figure 1. Framework of Study

The research basically started on making, curing and testing samples. Then, the

researchers took note of their findings and tabulated the results. Finally, they evaluated the data

gathered and formed a conclusion.

15

Chapter 4

METHODOLOGY

Research Procedures:

Survey Research Stage, Preparation Stage, and the Experimental Stage are the processes

that were followed in this research.

A. Survey Research Stage

In this stage, the researchers were to search for the location of possible sources of

materials. The lightweight aggregates that were used as sand were found in Casiguran, Sorsogon.

The Lightweight aggregate is the rock called pumice.

Preparation Stage

Gathering and preparation of the raw materials were part of this stage. The

Pumice rocks were abundant in Casiguran, Sorsogon. Pumice Rocks were crushed and

underwent sieve analysis for fine aggregates in order to be classified as sand. Fine

aggregates were washed to remove several impurities such as roots, leaves, etc. In order

to remove the sand found in the coarse aggregates, the researchers decided to have the

sieve analysis. Removing the impurities in the aggregates would be very helpful in

ensuring good quality of the aggregates, thus, resulting to better results.

16

Pumice Crushing Stage

After cleaning and removing impurities from the sample, the pumice was crushed

using the compaction mold and the compaction hammer, weighing 4.54 kg with 50 mm

diameter face.

B. Experimental Stage

The researchers used the volumetric method in designing the mortar mixture for the

lightweight mortar. The researchers also conducted some laboratory analyses of the materials

such as sieve analysis and absorption of the aggregates.

Sieve Anlaysis

Sieve analysis was used by the researchers to filter the crushed pumice

aggregates. This enabled the researchers to thoroughly select the resulting fine aggregates

to be used.

Mix Design Procedure

A trial mix was made to assess the behavior of the pulverized pumice when used

as sand in mortar. Observations were made to consider the areas where the mortar would

be improved. The assumption was that the lower the water cement ratio and the higher

the cement factor, the stronger the mortar will be.

For mortar testing, the researchers adapted the 1:1, 1:2, 1:3, and 1:4 ratio of

cement to crush pumice through volumetric method. The mixed sand and crushed pumice

adapted the same ratio except that the crushed pumice and sand would occupy the volume

17

of the crushed pumice alone. It was divided into 50% crushed pumice and 50% sand. The

ratio of cement to sand considered the same ratio. The amount of water required to make

good mortar varied depending on the desired consistency of the mortar.

C. Preparation of Samples

This stage includes mixing, casting, curing and testing of the specimen.

Mixing

The crushed pumice and cement were thoroughly mixed manually according to

their designated ratio. Water was added gradually.

Casting

The researchers used the standard mortar molds having the dimensions 2” X 2” X

2”. Each three layers of specimen were tamped using very slender stick until the molds

were filled evenly on top.

Curing

To allow the mortar to attain its desired strength, the specimens were removed

from the molds after 24 hours and were placed immediately inside a curing tank for a

designated period of time. Curing is the process of preventing moisture from evaporating

from concrete and supplying moisture so that hydration will continue until the internal

structure of the concrete is built up to the point where the strength and other properties

are developed. The final concrete strength depends on the conditions of moisture and

18

temperature during the initial period of the curing process. The specimens to be tested

were removed from the curing tank 24 hours before subjecting to compressive loading.

Testing

The researchers used two steel plates having a dimension of 2” x 2”, placed at the

top and bottom of every mortar sample for equal distribution of the applied force to the

samples. The samples were subjected to a load rate 20mm/min based from the ASTM

standards.

19

Chapter 5

RESULTS AND DISCUSSIONS

For further comparison, the ratio 1:1 served as the initial design mix. Using this design

mix, the researchers came up with three different samples namely, pure pumice (A), pure sand

(B), and mixed pumice and sand (C). The researchers also came up with the ratios 1:2, 1:3, and

1:4 and prepared nine samples for each ratio, three samples per design mix, for further

comparison. The samples were removed from their molds twenty four hours after the samples

were mixed and were placed in a curing tank. Then, the samples were removed from the curing

tank for at least twenty four hours and were weighed before subjecting them to compression test.

The table below showed the volume composition of the sample used in the mortar mix. This

showed the quantity of sand, pumice, cement and water used in the mix for each sample and

ratio.

Table 2. Volume Composition Each Sample

SampleVolume in cm3

Sand Pumice Cement Water

A1:1 -- 500 500 200B1:1 500 - - 500 200C1:1 250 250 500 200A1:2 -- 500 250 150B1:2 500 - - 250 100C1:2 250 250 250 150A1:3 -- 750 250 225B1:3 750 -- 250 175C1:3 375 375 250 175A1:4 -- 500 125 175B1:4 500 -- 125 125C1:4 250 250 125 150

20

1:1 1:2 1:3 1:40

50

100

150

200

250

300

Average Weight of Sample

LightweightNormal50-50

Mix Ratio

Wei

ght i

n m

g

Figure 2. Average Weight of Sample

The figure above showed the weight of each sample. The sample was air dried before it

was weighed, which implies that the sample must have contained water, specially the lightweight

sample that contained pumice, since pumice has higher water absorption than that of normal

sand.

21

Table 3: Compressive Test Reults, Mass, Weight Difference for 1:1 Ratio

SampleCompressive Strength in

MpaAve.

Weight in g

Wt. Diff. Measured from

Sand Mortar Sample7-day 14-day 21-day

A 22.18 22.28 24.34 211.77 23.72%B 30.13 30.76 33.74 277.63 C 28.56 28.46 29.41 244.30 12.01%

7-day 14-day 21-day05

10152025303540

Test Results For 1:1 Ratio


Days Cured

Com

pres

sive

Stre

ngth

in M

Pa

Figure 3 Test Results for 1:1 Ratio

The table and figure above showed the compressive strength of the samples from the ratio

1:1. The highest compressive strength attained for the twenty one, fourteen, and seven days

curing period were 33.74 MPa (approximately 4,900 psi), 30.76 MPa (4,897 psi), and 30.13 MPa

(4369 psi) respectively, through pure sand aggregates.

Table 3 showed that sample A, pure lightweight mix, is lighter than sample B, pure sand

mix, by 23.72 %. It also showed that sample C, mixed lightweight and sand, and is lighter than

sample B by 12.01%.

22



MpaAve.

Weight in g



A 15.68 18.96 16.64 200.07 29.58%B 20.29 24.10 25.90 284.10 C 18.41 23.14 25.53 239.23 15.79%


5

10

15

20

25

30



Days Cured

Com

pres

sive

Stre

ngth

in M

Pa

Figure 3. Test Results for 1:2 Ratio

The compressive test results of the samples for the ratio 1:2 were shown in the table and

figure above. The maximum compressive strength attained for the twenty one, fourteen, and

seven days curing period were 25.90 MPa (3,756.50 psi), 24.10 MPa (3,495.40 psi), 20.29 MPa

(2,942.45 psi) respectively, through pure sand aggregates.


mix, by 29.58%. It also showed that sample C, mixed lightweight and sand, and is lighter than

sample B by 15.79%.

23



MpaAve.

Weight in g



A 11.74 10.45 16.00 178.03 33.25%B 15.94 14.14 22.23 266.70 C 10.50 18.36 19.80 232.37 12.87%


5

10

15

20

25



Days Cured

Com

pres

sive

Stre

ngth

in M

Pa

Figure 4 Test Results for 1:3 Ratio

The table and figure above shows the compressive strength of the samples from the ratio

1:3. The highest compressive strength attained for twenty one, and seven days curing period

were 22.23 MPa (3,223.46 psi), and 15.94 MPa (2,311.54 psi) respectively, through pure sand

aggregates. While the maximum compressive strength attained for fourteen days curing period

was 18.36 MPa (2,663.26 psi) through mixed sand and pumice aggregates.



sample B by 12.87%.


24

SampleCompressive Strength in Mpa Ave.

Weight in g



A 7.74 9.51 11.60 178.77 30.11%B 7.01 8.44 11.93 255.77 C 11.30 12.14 12.78 230.47 9.89%


2

4

6

8

10

12

14



Days Cured

Com

pres

sive

Stre

ngth

in M

Pa

Figure 5. Test Results 1:4 Ratio

The compressive test results of the samples for the ratio 1:4 were shown in the table and

figure above. The maximum compressive strength attained for the twenty one, fourteen, and

seven days curing period were 12.78 MPa (1,852.85 psi), 12.14 MPa (1,760.4 psi), 11.30 MPa

(1,638.93 psi) respectively, through mixed sand and pumice aggregates.



sample B by 9.89%.

25

Based on tables 3-6, the minimum compressive strength attained from the ratios 1:1 – 1:3

was from the pure crushed pumice mix design yet in the 1:4 ratio the minimum compressive

strength of 7.01 MPa was from the pure ordinary sand mix design. The largest weight difference

between pure lightweight and pure sand mix was 33.25% which was attained using design mix

ratio of 1:3. Also, the lightest sample of combined pumice and sand mix compared to pure sand

mix was 15.79%, attained through the 1:2 design mix ratio.

26

Chapter 6

CONCLUSION

Based on the tabulated results, the researchers established a conclusion that pumice can

be a substitute for sand in a mortar. This was established through the results attained using

compression test. However, the crushed lightweight could be used in construction if it is readily

available in the site. Though pure pumice mix has weaker compressive strength than that of pure

sand mix, the strength attained by the pure pumice mix was relatively high since most samples

passed the minimum required compressive strength of 17 MPa or 2,500 psi for residential

structures just like concrete.

Most samples of combined crushed pumice and sand passed the minimum required

compressive strength. Though the compressive strength of pure sand is greater than the

combined sample, it has reduced in strength by only a small amount (Tables 3-6). Besides, it was

an acceptable decrease based on the results.

The information from the research showed the volume composition and mass of each

sample. It also proves that pumice was indeed lighter than sand. Basically, replacing a part of

sand by those crushed pumice would decrease the strength considerably but its weight has

decreased greatly. Increasing the volume of the crushed pumice with respect to cement caused a

favourable decrease of not less than 23.72% on the weight of the samples.

Tables 3 to 5 showed that the compressive strength of normal cement mortar is greater

than that of the 50-50 design mix. However, the results in Table 6 showed that the 50-50 design

mix has greater compressive strength capacity than the normal cement mortar. This is because of

27

50-50 design mix having lesser water-cement ratio due to the absorption of crushed pumice.

Facts said that lesser water-cement ratio has the greater possibility of gaining higher compressive

strength capacity. Regarding with the weight aspect of the samples, the 50-50 mortar mix has

lesser mass than the normal mortar mix due to the lightweight aggregates. The minimum weight

difference of 9.89% with respect to the normal mortar mix was attained by the sample C, having

50% pumice sand and 50% ordinary sand. In conclusion, the strength of 50-50 mortar mix is

relatively at par with the normal design mix and the 50-50 mortar mix weight is lesser than the

weight of normal mortar mix.

The factor that has affected the results was the absorption of the pumice aggregates. The

absorption of the aggregates is very important in dealing with the correct amount of water to be

added to the mixture. It has affected the water-cement ratio of the sample which resulted to

varying compressive strength test results. Furthermore, the absorption of the aggregates was not

measured due to incapability to get the specific gravity of the pumice aggregates due to lack of

equipment to determine it. Thus, acquiring the absorption of the pumice aggregates would be one

of the factors in determining the proper design mix of the sample resulting to higher compressive

strength of each sample.

28

Chapter 7

RECOMMENDATIONS

For further studies, the researchers suggest to take into consideration the mechanical

properties of the aggregates used in order to determine the proper design mix in making samples.

Specific gravity of an aggregate is an important factor in determining the proper ratio of the

design mix considering its weight. Also, absorption and moisture content of the aggregates is

highly significant in computing the water-cement ratio. Furthermore, researchers should try to

apply the optimization of the gradation of the aggregates using the sieve analysis for higher

compressive strength results. The researchers also recommend that future researchers should

check gradation of the aggregates if it has passed the ASTM standards using sieve analysis. Also,

in getting the weight of the mortar samples future researchers should make sure that the samples

were dry so that the weight of the water in the sample would not affect the weight. In addition,

future researchers can consider the amount or percentage of pumice to be mixed with sand in

order to optimize its weight and strength.

The proponents suggests that future researchers will focus more on other uses of crushed

pumice as an alternative to sand construction such as concrete and concrete hollow blocks.

Lightweight concrete would be mixed using ordinary coarse aggregate and crushed pumice

which will act as sand. The samples to be made should be of good quality, having the correct

water-cement ratio, prepared cautiously, carefully mixed and casted accordingly.

29

REFERENCES

Theses:

Presentacion, Glenn and Nerson Sagales. “Design Mix of Lightweight Concrete

Containing Pumice Gravel, Albay Sand and Portland cement”. March 2010.

Ty-Bonavente Ray Adrian Limneo and Roderick A. Pacardo. “The use of waste glass as

substitute for sand in construction”. March 2010.

Electronic Sources:

“Lightweight Blocks”, http://www.apexgulf.com/light.html

“The Effects of Pumice Aggregates/Cement Ratios on the Low-Strength Concrete

Properties”, http://www.highbeam.com/doc/1G1-178450418.html

“Lightweight Concrete”, http://star-ltd.com/pumice/lightweight_concrete.html

“Building with Pumice”, http://www.appropedia.org/Original:Building_with_Pumice

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APPENDIX A

RESEARCH DOCUMENTATION

Figure 6. The Amount of Crushed Pumice Aggregates, Albay Sand and Portland Cement to be used in a 1:1 ratio for 50-50 cement mortar mixture

Figure 7. Measured amount of water to be added for tabulation purposes

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Figure 8. Initial addition of water to the mixture

Figure 9. Mixed Crushed Pumice, Sand, Cement and Water

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Figure 10. Casting of mixture to the mold

Figure 11. The mix already casted in the mold

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Figure 12. Curing of the Samples

Fgure 13. 24 hours after the samples remove from the curing tank

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Figure 14. Sample subjected to the UTM

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APPENDIX B.

COMPRESSIVE STRENGTH TEST RESULTS

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pumice as sand

Documents