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ENGINEERING PROPERTIES OF LIGHTWEIGHT MASONRY UNIT PRODUCED FROM WASTE EXPANDED POLYSTYRENE (EPS) AND RICE HUSK ASH (RHA) TP 1180 S7 L755 2012 Ling Ing Hock Master of Engineering 2012

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ENGINEERING PROPERTIES OF LIGHTWEIGHT MASONRY UNIT PRODUCED FROM WASTE EXPANDED POLYSTYRENE (EPS) AND

RICE HUSK ASH (RHA)

TP 1180 S7 L755 2012

Ling Ing Hock

Master of Engineering 2012

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Pusat Khidmat Makiumat Akademit UNIVERSfC1 MALAYSIA SARAWAK

ENGINEERING PROPERTIES OF LIGHTWEIGHT MASONRY UNIT

PRODUCED FROM WASTE EXPANDED POLYSTYRENE (EPS)

AND RICE HUSK ASH (RHA)

LING ING HOCK

A thesis submitted

in fulfillment of the requirements for the degree of Master of Engineering

Faculty of Engineering UNIVERSITI MALAYSIA SARAWAK

2011

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For the sake of mankind

1

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ACKNOWLEDGEMENTS

First of all, I would like to acknowledge UNIMAS for their financial support for the UNIMAS

research `Small Grant Scheme' with grant no. 02(S50)/715/2010(01). This research would not

be possible without the support of the mentioned grant.

I sincerely thank my project supervisor Dr. Delsye Teo Ching Lee, Co-supervisors, Madam

Norsuzailina Mohamed Sutan and Miss Idawati Ismail for their guidance, suggestions, and

continuous support throughout my graduate studies. I greatly appreciate all the support that they

have given to me, both on this thesis and during the entire research period.

I also would like to extend my thanks to the lab technicians, Mr. Nur Adha Abdul Wahab, Mr.

Ismail b Abusamat, Mr. Rozaini Ahmad, Mr. Sabariman Bakar and Madam Ting Woei who

assisted me a lot in my laboratory work.

Cooperation from Faculty of Civil Engineering, Faculty of Resources, Science and Technology

and Faculty of Mechanical and Manufacturing Engineering are really appreciated.

My special appreciation goes to my friends and to those who have helped me in my research.

Last but not least, thanks to my family members for supporting me in my study and research.

ii

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ABSTRAK

Kebelakangan ini, masalah pengurangan sumber yang tidak boleh diperbaharui telah menjadi

satu isu yang membimbangkan. Ramai pencinta alam dan penyelidik telah menyiasat

penggunaan sisa-sisa bahan buangan sebagai sumber yang boleh diperbaharui untuk kegunaan

terutama sebagai bahan mentah dalam sektor pembinaan. Karya ini melaporkan potensi

penggunaan sisa abu sekam padi dan manik polistirena untuk menghasilkan bata konkrit ringan.

Abu sekam padi ini digunakan sebagai bahan pensimenan kerana ia adalah bahan yang lebih

ringan dan reaktif. Adunan campuran ini terdiri daripada 5%, 10%, 15% dan 20% perggantian

simen dengan sisa abu sekam padi dan kandungan pasir dan manic polisterena yang sama. Sisa

manik polistirena digunakan sebagai penggantian sebahagian agregat dalam adunan. Empat jenis

keadaan pengawetan telah digunakan dalam kajian ini. Ini termasuk pengawetan air, pengawetan

kering, pengawetan 3-hari dan pengawetan 7-hari. Sifat-sifat kejuruteraan bata disiasat. Antara

sifat-sifat yang dikaji adalah ketumpatan konkrit mengeras, dimensi, kekuatan mampatan,

penyerapan air, keterapan dan kekonduksian ten-na batu bata konkrit ini. Mengimbas mikroskop

elektron (SEM) dilakukan ke atas sampel bata. Hasil kajian menunjukkan bahawa R10 dengan

10% penggantian abu sekam padi adalah adunan optimum. la mempunyai purata ketumpatan

sebanyak 1745 kg/m3 pada 28 hari di bawah pengawetan udara kering yang boleh

diklasifikasikan sebagai bata ringan. Bagi pematuhan dimensi, kesemua sampel mematuhi julat

nilai sepertimana yang ditetapkan dalam Piawaian Malaysia, MS 76: 1972. Dari segi kekuatan

mampatan, hasil kajian mendapati bahawa R10 bukan sahaja mempunyai kekuatan mampatan

yang tertinggi tetapi juga mematuhi keperluan kelas 2 bagi bata galas beban pada 28 hari

sebagaimana yang dinyatakan dalam Piawaian Malaysia. Nilai-nilai bagi penycrapan air,

keterapan dan kekonduksian haba untuk R10 pada 28 hari yang diawetkan di bawah keadaan

pengawetan yang berbeza adalah terdiri daripada 13% ke 16%, 0.1 x 10-3g/mm2/min°'5 ke iii

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0.142x 10-3g/mm2/min0-5 dan 0.36 W/mK ke 0.468 W/mK masing-masing. Di samping itu,

terdapat kira-kira 31 % pengurangan kekonduksian terma berbanding sampel kawalan pada 28

hari di mana ini menunjukkan jumlah penjimatan tenaga yang ketara. Analisis SEM juga

menunjukkan R10 mempunyai susunan mikrostruktur yang baik. Secara amnya, keputusan

mendapati bahawa sifat-sifat batu bata terutamanya dipengaruhi oleh kandungan sisa abu sekam

padi dalam campuran dan keadaan pengawetan yang digunakan. Kekuatan mampatan untuk

EPS-RHA bata simen meningkat dengan perningkatan peratusan perggantian sisa abu sekam

padi dalam adunan. R10 dengan 10% perggantian sisa abu sekam padi (adunan optimun)

menghasilkan kekuatan mampatan yang tertinggi. Kekuatan mampatan mengurang apabila

peratusan perggantian sisa abu sekam padi melebihi 10%. Nilai penyerapan air dan keterapan

menurun apabila peratusan perggantian sisa abu sekam padi meningkat. Perningkatan peratusan

perggantian sisa abu sekam padi menghasilkan nilai kekonduksian terma yang rendah. Secara

amnya, pengawetan air adalah cara pengawetan yang paling berkesan. la menghasilkan nilai

kekekuatan mampatan dan kekonduksian terma yang tertinggi tetapi nilai penyerapan dan

keterapan yang terendah.

iv

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ABSTRACT

The depletion of non-renewable resources has become an alarming issue nowadays. Many

environmentalists and researchers have been investigating the use of waste materials as a

renewable resource for use as raw materials in construction. This research reports on the

potential use of waste rice husk ash (RHA) and expanded polystyrene (EPS) beads in producing

lightweight concrete bricks. The RHA was used as a cementitious material since it is a

lightweight reactive pozzolanic material. The mixes prepared were made of RHA of 5%, 10%,

15% and 20% as partial replacement for cement and with the same amounts of sand and EPSI

The EPS was used as partial aggregate replacement in the mixes. Four types of curing conditions

were employed in this study. These include water curing, air-dry, 3-day water curing and 7-day

water curing. The engineering properties of the bricks were investigated. Among the properties

studied were hardened density, dimension compliance, compressive strength, water absorption,

sorptivity and thermal conductivity of the EPS RHA concrete bricks. Scanning electron

microscopy (SEM) was also performed on the brick samples. The results showed that RIO with

10% RHA replacement was the optimum mix. It had an average 28-day air-dry density of 1745

kg/m3 which classifies it as lightweight. For the dimension compliance, all bricks were within the

specified values according to MS 76: 1972. In terms of compressive strength, it was found that

RIO not only gained the highest compressive strength as compared to other samples but also

complied with the Class 2 (14 N/mm2) requirement for load bearing bricks at 28 days as

specified in Malaysia Standard. The water absorption, sorptivity and thermal conductivity for

RIO at 28 days cured under different curing conditions ranged from 13% to 16%, 0.1 x 10-3

g/mm2/miri '5 to 0.142x 10-3 g/mm2/min°'5 and 0.36 W/mK to 0.468 W/mK respectively. In

addition, it was observed that there was a thermal conductivity reduction of approximately 31 %

as compared to control mix at 28 days which shows a significant amount of energy saving. The V

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SEM analysis also showed denser microstructure arrangement for the RIO. It was found that the

properties of the bricks are mainly influenced by the percentage of RHA replacement in the mix

and also the curing condition used. The compressive strength of the EPS-RHA concrete brick

increased with the increase percentage of RHA replacement in the mix. RIO with 10% RHA

replacement (optimum mix) produced the highest compressive strength. The compressive

strength decreased as the percentage of RHA replacement exceeds 10%. The water absorption

and sorptivity values were decreased as the percentage of RHA replacement increased. The

increase in RHA replacement produced lower thermal conductivity values. In general, full water

curing is the most effective method of curing. It produced the highest level of compressive

strength and thermal conductivity but the lowest value of water absorption and sorptivity.

V1

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! 'usat KAidmat Maklumat A"deotif inVIVERSITi MALAYSIA SARAWAK

LIST OF TABLES

Table No. Page

Table 1.1 Different roles of the agricultural and industrial wastes in concrete 2

Table 3.1 Physical properties and chemical composition of cement and RHA 27

Table 3.2 Physical and chemical properties of superplasticizer 29

Table 3.3 Properties of EPS and sand 30

Table 3.4 Curing regimes for the EPS RHA concrete bricks 32

Table 3.5 Hardened concrete tests 33

Table 4.1 Trial mixes for lightweight concrete bricks 40

Table 4.2 Fresh and hardened properties for the trial mixes of lightweight

concrete bricks 40

Table 4.3 Acceptable mix proportions for lightweight concrete brick 41

Table 4.4 Acceptable mix proportion containing different percentages of RHA

replacement 42

Table 5.1 Fresh concrete properties for different samples 45

Table 5.2 Slump loss for different samples with time 45

Table 5.3 Dimension of the brick samples 46

Table 5.4 Compressive strength of all samples under different curing regimes. 49

Table 5.5 Water absorption of all samples under different curing regimes. 53

Table 5.6 Sorptivity of all samples under different curing regimes. 57

Table 5.7 Thermal conductivity of all samples under different curing regimes. 61

vii

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Table Dl Sample RO specimen No: 1 84

Table D2 Sample RO specimen No: 2 85

Table D3 Sample RO specimen No: 3 85

Table D4 Weight gain for the three specimens of Sample RO with time. 85

Table D5 Cumulative weight gain over cross section area of specimens (100mmx I OOmm), Q/A for the three specimens of Sample RO with time. 86

viii

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LIST OF FIGURES

Figure No. Page

Figure 1.1 RHA produced from the rice mill.

Figure 3.1 SEM micrographs of RHA and OPC obtained from the

3

laboratory work done 26

Figure 3.2 XRD patterns of silica extracted from RHA 28

Figure 3.3 FTIR spectrum of RHA 28

Figure 3.4 Grading curve for river sand and EPS 30

Figure 3.5 Mixing procedure for EPS-RHA bricks. 31

Figure 3.6 The arrangement of length, width and height for dimension test. 34

Figure 3.7: Sorptivity test for EPS-RHA samples 36

Figure 4.1 Cross section of EPS RHA concrete brick 41

Figure 5.1 28-day air-dry densities for different samples 47

Figure 5.2 Compressive strength of each sample under different

curing regimes 51

Figure 5.3 Relationship between compressive strength under Cl

curing for different samples 52

Figure 5.4 Water absorption for each samples under different curing regimes 55

Figure 5.5 Sorptivity for different samples under different curing

conditions 59

Figure 5.6 Thermal conductivity for different samples under different

curing conditions 63

ix

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Figure 5.7 Thermal conductivity and density for different samples

at 28 days age under Cl curing 64

Figure 5.8 SEM micrographs for different samples obtained from experiment done 66

Figure A. 1 Hilton B480 machine (Heat Flow Meter Machine) 86

Figure A. 2 Cut section of heat flow meter machine 87

Figure B. 1 SEM machine (JEOL JSM-6390LA) 88

Figure C. 1 Auto fine coater machine (JEOL JFC-1600) 89

Figure D. 1 Sorptivity for Sample RO (specimen No: 1) 92

Figure D. 2 Sorptivity for Sample RO (specimen No: 2) 93

Figure D. 3 Soiptivity for Sample RO (specimen No: 3) 93

X

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TABLE OF CONTENTS

DEDICATION

ACKNOWLEDGEMENTS

AB STRAK

ABSTRACT

LIST OF TABLES

LIST OF FIGURES

TABLE OF CONTENTS

Page

1

11

111

V

vii

ix

R1

CHAPTER 1 INTRODUCTION

1.1 Brick 1

1.2 Renewable Raw Materials for Building and Construction Materials 2

1.3 Waste Rice Husk Ash 3

1.4 Waste Expanded Polystyrene Beads 4

1.5 Use of RHA and EPS Wastes in the Production

of Lightweight Concrete Bricks 4

1.6 Research Significance 5

1.7 Research Objective 6

1.8 Scope of Work 7

CHAPTER 2 LITERATURE REVIEW

2.1 Historical Background of Masonry

xi

8

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2.2 Cement Masonry

2.3 Waste Materials as Raw Material in Concrete

2.3.1 Rice Husk Ash

2.3.2 Expanded Polystyrene Beads

2.4 Previous Research on Concrete with Waste Materials

2.4.1 RHA Concrete

8

9

9

10

11

11

2.4.1.1 Workability of RHA Concrete 11

2.4.1.2 Compressive Strength of RHA Concrete 12

2.4.1.3 Water Absorption of RHA Concrete 14

2.4.1.4 Sorptivity of RHA Concrete 16

2.4.1.5 Thermal Conductivity of RHA Concrete 18

2.4.2 EPS Concrete 19

2.4.2.1 Workability of EPS Concrete 19

2.4.2.2 Strength of EPS Concrete 20

2.4.2.3 Water Absorption of EPS Concrete 22

2.4.2.4 Thermal Conductivity of EPS Concrete 22

2.5 Concluding Remarks

CHAPTER 3 MATERIALS USED AND METHODOLOGY

3.1 Introduction

3.2 Raw Materials

3.2.1 Ordinary Portland Cement

3.2.2 RHA

3.2.3 Superplasticizer

3.2.4 EPS and Sand

24

25

25

25

26

29

29

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3.2.5 Water

3.3 Mixing and Production of EPS RHA Bricks

3.4 Curing Regimes

3.5 Test Methods

3.5.1 Fresh Concrete Properties

3.5.2 Hardened Concrete Properties

31

31

32

32

32

33

(a) 28-Day Air-Dry Density 33

(b) Dimension Compliance 33

(c) Water Absorption 34

(d) Sorptivity 35

(e) Compressive Strength Test 36

(f) Thermal Conductivity Test 37

(g) Scanning Electron Microscopy (SEM) 38

CHAPTER 4 MIX DESIGN

4.1 General Background for Mix Design

4.2 Acceptable Mix Proportions for Lightweight

Concrete Brick

4.3 Concluding Remarks

CHAPTER 5 RESULTS AND DISCUSSIONS

5.1 Introduction

5.2 Fresh Concrete Properties

5.3 Hardened Concrete Properties

5.3.1 Dimension Compliance

39

41

43

44

44

45

45

Xlll

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5.3.2 28- day Air-dry Density

5.3.3 Compressive Strength

5.3.4 Water Absorption

5.3.5 Sorptivity

5.3.6 Thermal Conductivity

5.3.7 Scanning Electron Microscopy Analysis

5.4 Concluding Remarks

CHAPTER 6 CONCLUSIONS AND RECOMMENDATIONS

6.1 Conclusions

6.2 Recommendations

REFERENCES

APPENDIX

APPENDIX A: THERMAL CONDUCTIVITY MACHINE

APPENDIX B: SEM MACHINE (JEOL JSM-6390LA)

APPENDIX C: SEM SAMPLE PREPARATION

APPENDIX D: SAMPLE CALCULATION FOR SORPTIVITY

APPENDIX E: LIST OF PUBLICATIONS

46

47

52

56

60

64

67

69

71

72

86-94

86

88

89

90

94

xiv

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CHAPTER I

INTRODUCTION

1.1 Brick

In the 21st century, the introduction of sustainable development into building and construction

materials has gained great attention. The world is becoming increasingly aware of the increasing

cost of brick due to high demands, scarcity of natural non-renewable resources and high prices of

energy. Nowadays, brick has become one of the most important construction materials for

construction of buildings. The consequent increase of population contributed to a fast increase of

agricultural plantation as well as industrial production. On the other hand, a huge volume of

agricultural and industrial waste is generated. Attempts have been made to incorporate these

wastes in the production of bricks. For instance, the use of rubber (Turgut and Yesilata, 2008),

limestone dust and wood sawdust (Turgut and Algin, 2006), processed waste tea (Demir, 2005),

fly ash (Lin, 2006), polystyrene (Veiseh and Yousefi, 2003), cigarette butt (Kadir et al., 2010)

and tannery sludge (Basegio et al., 2002). In light of producing sustainable and eco-friendly

cement brick, the ideas of incorporating renewable waste materials from different industries has

been gaining increasing attention in the recent years. The use of such renewable waste materials

will not only help to solve the waste accumulation problem, but also gives added value to the

cement brick.

1

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1.2 Renewable Raw Materials for Building and Construction Materials

In the 21St century, the introduction of sustainable development concept into the building and

construction materials has gained great attention. The cost of building materials is increasing day

by day because of high demand, scarcity of raw materials, and high price of energy. From the

standpoint of sustainable development and environmental issue, the use of alternative

constituents in building materials is now a global concern. As a consequence, a lot of attention is

drawn in focusing agro-waste materials and industrial by-products as new raw materials for

building materials.

The use of these agro-waste and industrial by-product gives added value to the building

materials. Where the factories and agricultural activities are widespread, the accumulation of

these waste are abundant. Depending on the properties, each waste has the possibility to act as

cement replacing materials. Table 1.1 describes the applications of the wastes in concrete.

Tablel. 1: Different uses of the agricultural and industrial wastes in concrete.

Types of Wastes Use As

Fly ash, rice husk ash (RHA), ground granulated blast furnace slag, silica fume, rice straw ash and palm oil Pozzolans fuel ash Expanded polystyrene beads (EPS), granulated plastic, glass, fiber glass, ceramic, oil palm shell, crumb rubber Aggregates

and coconut shell Fiber, scrap metal, sugar cane fiber, wood fiber, san Reinforcement fiber, hemp fiber, waste tire steel beads and coir.

2

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IA Waste Expanded Polystyrene Beads (EPS)

EPS is nowadays used as a popular packaging or insulating material in various industrial fields in

the world due to its characteristics such as lightweight, low thermal conductivity, high impact

resistance, versatility, dimensional stability, clean nature and low cost. However, most of the

expanded polystyrene beads are disposed as a bulk waste immediately after one time use. On

other hand, the disposal of the large quantities of waste EPS has caused serious environmental

problems in the world. These environmental problems include water and land pollution due to

the non-biodegradable properties of the EPS. Some are being burnt which cause serious air

pollution. Therefore, recycling this waste EPS into useful building materials is one of the

alternatives to reduce the accumulation of the waste EPS.

1.5 Use of RHA and EPS Wastes in the Production of Lightweight Concrete Bricks

Masonry is one of the most important building materials in the construction industry in the

modem era nowadays. The production of one tonne of cement produces equally the same amount

of carbon dioxide (C02) into our atmosphere (Szabo et al., 2006). In light of the concept of

sustainable development, energy conservation and environmental friendliness for building

materials, engineers have been formulating new ingredients for the production of future building

materials. As a result, there has been a considerable interest in developing new building material

incorporating both agricultural waste and industrial by-products in the construction materials.

One such approach is to replace some of the cement with agricultural waste namely, RHA and

coarse aggregate with EPS beads in the production of concrete bricks.

4

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Pusat Khldmat MaklumatAkademiý UNIVERSITI MALAYSIA SARAWAK

RHA is high in amorphous silica content, porous and lightweight in nature (Omatola and

Onojah, 2009; Moharana, 2011). The EPS used is also lightweight in nature. The combined used

of these solid wastes will eventually reduce the weight of the concrete brick as compared to the

conventional concrete bricks. Most importantly, the utilization of RHA and EPS waste in the

production of lightweight concrete bricks is a mean of successful waste management, converting

them into a useful building material. In addition, the lightweight concrete bricks being

lightweight, significantly reduced the dead load of the building. This will eventually result in

smaller beams and columns needed and subsequently reduced the number of piles for footings.

1.6 Research Significance

Although there have been many researches done separately on the properties of the waste RHA

and waste EPS concrete (Ismail and Waliuddin, 1996; Zhang and Malhotra, 1996; Sabaa and

Ravindrarajah, 1997; Le Roy et al., 2005; Babu et al., 2006; Givi et al., 2010), there is no

research works done on the combined use of both solid wastes in the production of lightweight

concrete bricks. At present, through `My First Home Scheme' programme under the 2011 budget

announced by Prime Minister Datuk Seri Najib Tun Razak on 08 March 2011, there is a total

allocation of about 79,000 units of low-cost houses are expected to be built in Malaysia (News

Straits Times, 09 March 2011). Therefore, if the lightweight concrete bricks can be used for the

brick walls of low-cost houses, it will not only reduced the cost of construction for the low-cost

houses but also helps to recycle the waste materials into a more environmental friendly building

materials.

5

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In general, the use of this concrete brick will benefit the construction, industrial as well as

agricultural industries. Although a substantial number of researches have been done on the

engineering properties of waste RHA and waste EPS separately, the fresh and hardened

engineering properties of the combined use of these wastes in the production of concrete brick

are still not yet explored by researchers. Therefore, through this research project, the fresh and

hardened engineering properties are investigated so as to enable wider applications of the

concrete bricks as lightweight bricks particularly for load-bearing purposes.

1.7 Research Objectives

The main objective of this investigation is to determine the feasibility of combining waste RHA

and EPS in the production of lightweight concrete bricks. The waste RHA is use as cement

replacement and the waste EPS is use as aggregate replacement in the mix. In achieving the

above outlines, the research objectives are briefly summarized as follows:

i. To obtain an optimum mix containing waste EPS and RHA with 28-day air-dry

compressive strength of more than 7 N/mm2 and 28-days air-dry density of less than 1850

kg/m3.

ii. To investigate the fresh concrete properties of the EPS RHA lightweight concrete mixes.

iii. To investigate the hardened engineering properties of EPS RHA lightweight concrete

bricks.

6

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1.8 Scope of Work

The scope of work for this research is limited to fulfilling the objectives presented in section 1.7.

In Chapter 4, several trial mix design is listed out and some of the preliminary results were also

presented. Then, several trial mixes were conducted with different ratio of cement, sand, RHA

and EPS. The best mix which fulfills both lightweight density (1850 kg/m3) and having the

highest compressive strength (minimum compressive strength of 7 N/mm2) is selected as the

optimum mix. The optimum mix is then used throughout the entire investigation with the only

variables of RHA replacement of cement at 0,5,10,15, and 20%. The water -cement ratio of

0.5 was used throughout the entire investigation.

Based on the second and third objectives given, Chapter 5 presents the results and

discussions for the fresh and hardened properties for concrete bricks. The fresh concrete

properties tested included slump test, fresh density and air content. For the hardened concrete

properties, compressive strength, air-dry density, dimension stability, water absorption and

sorptivity were tested throughout this research. In order to simulate the different conditions for

the production of concrete bricks, four curing regimes were employed in the entire research.

Good bricks have properties of high compressive strength, low water absorption, low

sorptivity and low thermal conductivity. Therefore, the thermal conductivity for concrete brick

was also determined in this investigation. For density and dimension test, the specimens were

tested at the age of 28 days. However, compressive strength, water absorption, sorptivity and

thermal conductivity of the concrete bricks specimens were tested up to an age of 270 days.

7

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CHAPTER 2

LITERATURE REVIEW

2.1 Historical Background of Masonry

Masonry is the oldest manufactured building material, invented almost 6,000 years ago. During

these periods, the use of masonry in construction has hardly altered although changes in

materials, the building process and the concept of masonry construction have happened. Its

applications are widely spread throughout European countries and some other developed

countries (Somayaji, 2001).

Today, masonry construction includes not only quarried stone and clay bricks but a host

of other manufactured products as well. In various definitions of masonry, this group of materials

is often expanded to include concrete, stucco or precast concrete. The most conventional

application of the term `masonry' is limited to relatively small building units of natural or

manufactured stone, clay, concrete or glass that is assembled by hand using mortar.

2.2 Cement Masonry

Nowadays, the consumption of masonry in construction sector still become the favorites and

remains as the main option (Beall, 1997). The development of modular cement masonry was an

outgrowth of the discovery of Portland cement and was in keeping with the manufacturing trends

of the Industrial Revolution. With the invention and patenting of various block-making

machines, unit cement masonry began to have a noticeable effect on building and construction

8

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techniques of the late nineteenth and early twentieth centuries. Cement masonry today is made

from a relatively dry mix of cement, fine aggregates, water and some admixtures.

However, the mass production of cement bricks consumes an enormous amount of

cement. The manufacturing of cement is not only a high energy consuming process, but the

production of each tonne of cement releases approximately 1 tonne of carbon dioxide (CO2) into

the environment due to the calcinations of the raw materials and the combustion of fuels

(Malhotra, 2004). In 2010, nearly 2 billion tonnes of anthropogenic CO2 and other greenhouse

gases (GHGs) were emitted into the atmosphere which in turn leads to serious global warming

and greenhouse effects (World Cement Annual Review, 1997).

In light of the economical benefits, conservation of natural resources, energy saving and

environmental friendliness, the use of alternative pozzolanic materials from waste materials have

become the main focus of engineers and researchers alike as partial replacement for cement and

aggregate in concrete.

23 Waste Materials as Raw Material in Concrete

23.1 Rice Husk Ash

Rice is the main staple food for many countries around the world especially in the Asian region.

According to FAO (FAO Rice Market Monitor Report, 2011), there are 700 million tonnes of

paddy being harvested in 2010. During the milling of paddy, about 80% weight of paddy is rice

and bran. The remaining 20% is received as husk. Normally, the husk is used as fuel in the rice

mills to generate steam for the parboiling process. The husk contains about 75% organic volatile

matter, leaving 25% to be converted into ash during the firing process, known as rice husk ash 9