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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
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
For the sake of mankind
1
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
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
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.
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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
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
! '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
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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
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
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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
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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
TABLE OF CONTENTS
DEDICATION
ACKNOWLEDGEMENTS
AB STRAK
ABSTRACT
LIST OF TABLES
LIST OF FIGURES
TABLE OF CONTENTS
Page
1
11
111
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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
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8
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
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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
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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
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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
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Xlll
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
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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
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
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
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
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
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
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
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