formulation of compressed stabilized earth brick...
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FORMULATION OF COMPRESSED STABILIZED EARTH BRICK USING
BLACK UNCONTROLLED BURNT RICE HUSK ASH AS FULL CEMENT
REPLACEMENT
FETRA VENNY RIZA
A thesis submitted in
fulfillment of the requirement for the award of the
Doctor of Philosophy
Faculty of Civil and Environmental Engineering
Universiti Tun Hussein Onn Malaysia
APRIL 2017
iii
In the name of Allah, the most gracious and the most merciful.
I dedicate this thesis to my beloved family who has been a source of constant
support, advices, encouragement, motivation, and love through all this journey.
iv
ACKNOWLEDGEMENT
Alhamdulillah and praise to Allah The Almighty who gave me the strength in
completion of this thesis. In the name of Allah, The Most Gracious and The Most
Merciful, I would like to take this opportunity to express my gratitude for those
helping hands upon this journey.
First of all I would like to thank my supervisor Prof Ismail Abdul Rahman for
his patient in supervising, knowledge and enlightened motivation. His guidance was
most appreciated through the research and writing this thesis. I was lucky enough to
have him as my mentor.
I also extend my gratitude to all technicians that provided the best assistance
and cooperation in my research in the laboratories. Also my special appreciation goes
to UTHM for granted me the international scholarship which help financial aspect in
my research.
Last but not least, I would like to thank all my family, my late mother and
father for their understanding and continuous support in putting up with the
convenience when I was engaged in finishing my thesis. Especially I owe a
considerable debt of gratitude to my husband Josef Hadipramana for his forbearance
and remain patient amidst the hardship of this long journey.
v
ABSTRACT
Black uncontrolled burnt Rice Husk Ash (RHA) obtained from the boiler of rice mill
is a waste product which usually causing air and water pollution. As a waste, RHA
has very little value and commercial use. Hence this study examined the pozzolanic
potential of RHA as a cement replacement in the Compressed Stabilized Earth Brick
(CSEB) production. This is an experiment-based study that characterized the raw
materials used to produce CSEB samples. In the characterization of raw materials,
the XRD analysis found that the burning temperature of the RHA in the rice mill
boiler was around 700-800°C. Pozzolanic assessments on the RHA found that it
possesses pozzolanic characteristic within, and conformed to ASTM C 618 – 03.
Besides that, this study has also managed to develop a new method of determining
the pozzolanicity of RHA using electrical resistivity approach which is more
practical than Luxan conductivity method. In term of pozzolanic conductivity, it was
found that the RHA has a value of 0.47 mS/cm which indicates that the RHA has
attained good pozzolanic conductivity. In CSEB samples production, two sets of
soils were used which are laterite and clay, and two curing methods that are under
tarpaulin sheet and in the curing chamber for 7, 14 and 28 days. CSEB samples used
mix ratio of 1:8:2 in proportion binder: soil: sand with 15% water by weight by using
20, 40, 60 and 80% RHA ratio. The samples size of the bricks used is 100 x 50 x 30
mm which is based on Harrison’s brick factor ratio. All samples tested for
compressive strength complied with BS 5628-1:2005 for common brick. For water
absorption test, all CSEB samples satisfied the ASTM C-62 for normal weather,
however only some percentage of the samples passed for moderate and severe
weather. Hence this study has verified the hypothesis that waste uncontrolled burnt
RHA from the rice mill possessed pozzolanic characteristic which can act as a binder
when mix with lime in producing building brick and thus, producing affordable and
sustainable building materials for housing project.
vi
ABSTRAK
Abu sekam padi (ASP) hitam daripada sisa pembakaran yang tidak terkawal yang diperolehi
daripada dandang di kilang beras adalah merupakan bahan buangan yang selalunya
menyebabkan pencemaran udara dan air. Sebagai bahan buangan, ASP mempunyai nilai dan
kehunaan komersial yang sangat sedikit. Oleh itu kajian ini meneliti potensi pozzolanic dari
ASP sebagai pengganti simen dalam penghasilan bata stabil termampat (BST). Ini adalah
suatu kajian yang berdasarkan percubaan yang mencirikan bahan mentah yang digunakan
untuk penghasilan BST. Didalam pencirian bahan mentah, analisis XRDmendapati bahawa
suhu pembakaran SAP di dalam dandang kilang beras sekitar 700-800°C. Penilaian
pozzolanic pada ASP menemukan bahawa ianya memmpunyai ciri-ciri pozzolanic dan
mematuhi ASTM C 618 – 03.Selain itu, kajian ini juga telah berjaya membangunkan suatu
kaedah baharu dalam menentukan pozzolanicity dari ASP menggunakan pendekatan
kerintangan elektrik yang mana ianya lebih praktikal daripada kaedah kekonduksian Luxan.
Di dalam terma kekonduksian pozzolanic, ditemukan bahawa ASP yang mempunyai nilai
0.47 mS/cm menunjukkan kekonduksian pozzolanic yang baik. Dalam penghasilan sampel
BST, dua jenis tanah digunakan yaitu laterit dan tanah liat, dan dua kaedah pengawetan
diaplikasikan iaitu pengawetan di bawah helaian terpaulin dan dalam kebuk pengawetan
selama 7, 14 dan 28 hari. Sampel BST menggunakan nisbah campuran 1: 8: 2 berkadaran
pengikat: tanah: pasir sebanyak 15% air mengikut berat dengan menggunakan 20, 40, 60 dan
80% nisbah ASP. Ukuran sampel bata yang digunakan adalah 100 x 50 x 30 mm yang mana
adalah berdasarkan pada faktor nisbah bata Harrison. Semua sampel yang diuji kekuatan
mampatannya mematuhi BS 5628-1:2005 untuk bata biasa. Untuk uji penyerapan air, semua
sampel BST memenuhi ASTM C-62 untuk cuaca normal, bagaimanapun hanya beberapa
peratus dari sampel yang diluluskan untuk cuaca yang sederhana dan teruk. Oleh itu kajian
ini mengesahkan hipotesis bahawa ASP daripada sisa pembakaran yang tidak terkawal
mempunyai ciri-ciri pozzolanic yang dapat berfungsi sebagai pengikat jika dicampurkan
dengan kapur dalam penghasilan bata bahan binaan dan dengan itu menghasilkan bahan-
bahan binaan yang murah dan mampan untuk projek perumahan.
vii
TABLE OF CONTENT
TITLE i
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENT vii
LIST OF TABLES xii
LIST OF FIGURES xiv
LIST OF SYMBOLS AND ABREVIATION xix
LIST OF UNIT AND CONVERTION xx
LIST OF APPENDICES xxi
CHAPTER 1 INTRODUCTION 1
1.1 Background 1
1.2 Problem Statement 3
1.3 Aim and Objectives 4
1.4 Scope os study 5
1.5 Thesis Organization 6
CHAPTER 2 LITERATURE REVIEW 7
2.1 Introduction 7
2.2 Compressed Stabilized Earth Brick (CSEB) 8
2.3 Compositon of CSEB 10
2.3.1 Soil 10
2.3.1.1 Clay 11
2.3.1.2 Laterite 12
2.3.2 Stabilizers 15
2.3.2.1 Cement 16
viii
2.3.2.2 Lime 16
2.4 Properties of CSEB 18
2.4.1 Density 18
2.4.2 Water Absorption and Moisture Content 18
2.4.3 Strength 20
2.4.4 Durability 22
2.4.5 Thermal Value 23
2.4.6 Carbon Emission and Embodied Energy 24
2.5 Production of CSEB 25
2.5.1 Casting 25
2.5.2 Curing Process 27
2.6 Application of CSEB 27
2.7 RHA as an Alternative Stabilizer 30
2.7.1 Physical Properties 34
2.7.2 Chemical Properties 35
2.7.3 Pozzolanic Reaction 37
2.7.4 Pozzolanic Reactivity 39
2.8 Statistical Method 41
2.9 Summary 44
CHAPTER 3 RESEARCH METHODOLOGY 47
3.1 Introduction 47
3.2 Flowchart or Research Process 47
3.3 Material Preparation 49
3.3.1 Soil 49
3.3.1.1 Laterite 50
3.3.1.2 Clay 50
3.3.2 Cement 51
3.3.3 Lime 51
3.3.4 Sand 51
3.3.5 Water 52
3.3.6 Rice Husk and Rice Husk Ash (RHA) 52
3.4 CSEB Mix Proportion 55
3.5 Preparation of CSEB Speciment Procedure 57
ix
3.6 Curing Method 58
3.7 Material Testing Procedure 60
3.7.1 Soil Classification 60
3.7.2 Specific Gravity 60
3.7.3 Particle Size Distribution 62
3.7.4 Moisture Content 63
3.7.5 Loss on Ignition (LOI) 63
3.7.6 Thermogravimetric Analysis (TGA) 64
3.7.7 X-Ray Fluorescence (XRF) 65
3.7.8 X-Ray Diffraction (XRD) 67
3.7.9 Fourier Transform Infra Red Spectroscopy (FTIR) 69
3.7.10 Microstructure 69
3.7.11 Pozzolanic Reactivity 71
3.7.11.1 Conductivity Method 71
3.7.11.2 New Developed Resistivity Method 73
3.8 CSEB Compression Test 75
3.9 CSEB Water Absorption
3.10 Assessing the Experimental Data
76
77
3.10 Summary 79
CHAPTER 4 CHARACTERISTIC AND POZZOLANICITY OF
RICE HUSK ASH
80
4.1 Introduction 80
4.2 Physical Properties of RHA 80
4.2.1 Physical Appereance of RHA 83
4.2.2 Moisture Content of RHA 84
4.2.3 Loss on Ignition (LOI) of RHA 84
4.2.4 Thermogravimetric Analysis (TGA) of RHA 86
4.2.5 X-Ray Flouresence (XRF) of RHA 87
4.2.6 X-Ray Diffraction (XRD) of RHA 88
4.2.7 Amorphous Content of RHA 91
4.2.8 Fourier Transform Infra Red Spectroscopy (FTIR)
of RHA
95
4.3 Microstructure Properties of RHA 98
x
4.3.1 Microstructure of Rice Husk 99
4.3.2 Microstructure of Rice Husk Ash (RHA) 101
4.4 Pozzolanicity 110
4.4.1 Conductivity Method 110
4.4.2 New Method – Resistivity Approach 112
4.4.3 Validation of New Method 114
4.6 Summary 118
CHAPTER 5 APPLICATION OF WASTE RICE HUSK ASH IN
COMPRESSED STABILIZED EARTH BRICK
120
5.1 Introduction 120
5.2 Material Characterization in CSEB Production 120
5.2.1 Bulk Density and Specific gravity 121
85.2.2 Particle Size Distribution 122
5.2.3 Soil Characterization 124
5.2.4 CSEB Dimension and Density 127
5.2.5 Determination of Mix Proportion 128
5.2.6 Curing CSEB 128
5.3 CSEB Compressive Strength Performance 128
5.3.1 Influence of Soil Types 131
5.3.2 Influence of Curing Method 133
5.4 CSEB Water Absorption Performance 134
5.4.1 Discussion on Influence of Soil Types 138
5.4.2 Influece of Curing Method 139
5.5 CSEB Microstructure 140
5.6 Prediction of CSEB Compressive Strength and Water
Absorption
146
5.7 Equation for Practical Application 155
5.8 Summary 157
CHAPTER 6 CONCLUSSIONS AND RECOMENDATIONS 159
6.1 Introduction 159
6.2 Conclusion 159
6.2.1 Investigation the Pozzolanic Potential of Waste
RHA
159
xi
6.2.2 Exploration of Resistivity Methof for Measuring
the RHA Pozzolanicity
160
6.2.3 Determination the Optimum CSEB Mix Proportion) 161
6.2.4 Developed of Mathematical Equation for CSEB
Compressive Strength and Water Absorption
162
6.3 Recomendations 163
REFFERENCES 164
APPENDIX A 180
APPENDIX B 184
APPENDIX C 188
APPENDIX D 190
APPENDIX E 192
APPENDIX F 194
APPENDIX G 196
APPENDIX H 198
APPENDIX I 200
APPENDIX J 202
APPENDIX K 204
APPENDIX L 205
VITA 209
xii
LIST OF TABLES
2.1 Suggested lime content (%) by Ingles and Metcalf. 17
2.2 Comparison of ash and silica content from various plants. 32
2.3 RHA Properties from various researchers. 35
2.4 Chemical composition of RHA from various researchers. 36
3.1 Mix proportion of CSEB. 56
4.1 Moisture content of RHA. 84
4.2 LOI of RHA. 85
4.3 Weight change and % different weight with LOI. 86
4.4 Chemical content percentage of controlled and uncontrolled burnt
RHA.
89
4.5 Compound of each RHA samples. 91
4.6 Group Wavenumbers of Silica. 96
4.7 Conductivity values of RHA by Luxan method. 111
4.8 Resistivity values of RHA by resistivity method. 114
4.9
4.10
4.11
4.12
4.13
Data entry for comparison resistivity and conductivity method.
Correlation coefficient from resistivity and conductivity method.
Descriptive statistical analysis from resistivity and conductivity
method.
Regression analysis of resistivity and conductivity method.
Pozzolanic classification of new resistivity method.
115
116
116
117
118
5.1 Bulk density of materials. 121
5.2 Particle size analysis of binders. 124
5.3 Soil chemical composition percentage. 125
5.4 Atterbeg limits of laterite and clay. 126
5.5 CSEB density. 127
5.6 Compressive strength in MPa. 135
5.7 Water Absorption of CSEB. 135
xiii
5.8 Types of CSEB 146
5.9 Experimental data of CSEB 1. 147
5.10 Experiment and prediction value of compressive strength and
water absorption of CSEB 1.
148
5.11 Coefficient of determinant (R2) of equations model 149
5.12 T-test value of CSEB 1 150
5.13 t-statistic of compressive strength CSEB 1. 150
5.14 t-statistic of water absorption CSEB 1. 150
5.15 Experimental and Predicted Compressive Strength Equation 5.1. 152
5.16 Experimental and Predicted Water Absorption Equation 5.2. 152
5.17 Coefficient of Variation. 153
5.18 Equations for predicted compressive strength. 153
5.19 Equations for predicted compressive strength. 154
6.1 Pozzolanic potential of waste RHA. 160
6.2
6.3
6.4
6.5
Comparison Luxan Method and New Develop Resistivity
Method.
Proposed pozzolanic value classification.
Conformation of CSEB types to ASTM C-62.
Predicted Equation for CSEB.
161
161
162
165
xiv
LIST OF FIGURES
2.1 Clay distribution map in Peninsular Malaysia. 12
2.2 Map of laterite deposit around the world. 13
2.3 Distribution of laterite soil in Peninsula, Malaysia. 14
2.4 Air moisture absorbed from several materials. 20
2.5 Values of ‘factory gate’ embodied carbon for masonry
materials.
24
2.6 South Africa, Simunye Project Demonstration house built in 12
days.
28
2.7 Shri Karneshwar Nataraja Temple in Tamil Nadu, India. 28
2.8 Vaulted structure for the resort at Sandele. 29
2.9 Water tank with CESB, built on round blocks 290. 29
2.10 Earthquake resistant house built at Istanbul, Turkey. 29
2.11 Al Medy Mosque built in 7 weeks at Riyadh, Saudi Arabia. 30
2.12 Dejbjerg Iron Age Museum, built in 1998 Ringkøbing-Skjern,
Denmark.
30
2.13 World Rice Production up to 2011. 31
2.14 Malaysia rice production estimation. 31
2.15 Schematic of RHA production. 33
2.16 Lime cycle. 38
3.1 Flow chart of the experiment in this study. 48
3.2 Laterite soil before and after crushed. 50
3.3 Dried clay lump before crushed. 50
3.4 Hydrated Lime. 51
3.5 Sieved sand. 52
3.6 Water pH is checked with pH meter. 52
3.7 Rice husk and uncontrolled burnt RHA from rice milling boiler. 53
3.8 Kiln Furnace with air funnel. 53
xv
3.9 Opening of the furnace. 54
3.10 RHA after combustion. 55
3.11 CSEB after sampling. 56
3.12 Sequence of preparing CSEB specimen. 57
3.13 CSEB cured under tarpaulin. 59
3.14 Spraying CSEB before covered by tarpaulin. 59
3.15 Curing chamber 59
3.16 Desiccator. 61
3.17 Particle size Analyzer CILAS 1180 to determine the particle
size distribution of materials.
62
3.18 Container of particle size analyzer filled with distilled water. 62
3.19 TGA equipment. 64
3.20 XRF Machine. 65
3.21 Die set to cast the sample pellet for XRF. 66
3.22 Pellet sample was given compression pressure 80 kN. 66
3.23 Sample pellets for XRF test. 66
3.24 XRD Bruker D8 Advance. 67
3.25 Perkin Elmer Spectrum 100 FT-IR Spectrometer. 68
3.26 JEOL JSM-7600F FESEM. 69
3.27 JEOL JFC-1600 Auto Fine Coater. 70
3.28 Laboratory reagent Ca(OH)2. 71
3.29 Conductivity meter Hach Sension 5. 71
3.30 Digital stirring hot plate Corning PC-420D. 72
3.31 Magnetic bar stirrer. 72
3.32 Schematic diagram of modified soil box for resistivity
measurement.
73
3.33 Modified soil box resistivity test equipment. 74
3.34 Steel cap was applied above the brick to ensure uniform load
was distributed evenly.
76
3.35 The bricks were submerged in the cold water for 24 hours. 77
4.1 Whitish grey RHA as a result form complete combustion with
air circulation.
81
4.2 Blackish grey RHA as a result from incomplete combustion 81
xvi
without air circulation.
4.3 Waste RHA from rice milling.. 83
4.4 TGA graph of RHA 400°C. 86
4.5 Comparison of X-ray diffraction patterns of all RHA samples. 88
4.6 RHA XRD graph from the work of Serra et al (2015). 90
4.7 Crystallography of fully crystalline iron powder 92
4.8 Crystallography of fully amorphous glass. 92
4.9 X-ray diffraction graph classification of crystalline, amorphous
and monatomic gas.
93
4.10 RHA burnt at 400ºC (99.3% amorphous, 0.7% crystalline). 93
4.11 Amorphous content of controlled and uncontrolled burnt RHA. 94
4.12 FTIR spectrum of controlled and uncontrolled burnt RHA. 95
4.13 RHA FTIR spectrum from the work of Jing et al (2015). 95
4.14 IR correlation chart of SiO 2 adapted from National Institute of
Standards and Technology (NIST).
96
4.15 A fraction of single raw rice husk. 98
4.16 Outer epidermis of rice husk. 98
4.17 Inner epidermis of rice husk. 99
4.18 In between outer and inner epidermis of rice husk. 100
4.19 Porous properties is observed in rice husk. 100
4.20 RHA 400 at 1000 magnification. 101
4.21 RHA 400 at 10000 magnifications. 102
4.22 RHA 500 at 1000 magnification. 102
4.23 RHA 500 at 5000 magnification. 103
4.24 RHA 600 at 2000 magnification. 103
4.25 RHA 600 at 10000 magnification. 104
4.26 RHA 700 at 1000 magnification. 104
4.27 RHA 700 at 5000 magnification. 105
4.28 RHA 800 at 1000 magnification. 105
4.29 RHA 800 at 10000 magnification. 106
4.30 RHA 900 at 1000 magnification. . 107
4.31 RHA 900 at 10.000 magnification 107
4.32 RHA 1000 at 1000 magnification. 108
xvii
4.33 RHA 1000 at 10000 magnification. 108
4.34 RHA Muar, Malaysia at 700 magnification. 109
4.35 RHA Muar, Malaysia at 5000 magnification. 109
4.36 Pozzolanic reactivity with conductivity method. 111
4.37 Comparison conductivity and resistivity method after
compensate.
115
5.1 Cement particle size distribution graph. 122
5.2 Hydrated lime particle size distribution graph. 122
5.3 Uncontrolled burnt RHA passed 200 µm sieve particle size
distribution graph.
123
5.4 Uncontrolled burnt ground RHA particle size distribution
graph.
123
5.5 RHA Muar as received (a) and RHA after sieved (b). 124
5.6 Particle size distribution graph of laterite and clay soil. 126
5.7 Cassagrande Chart for laterite and clay soil. 127
5.8 Compressive strength of laterite CSEB with tarpaulin curing. 129
5.9 Compressive strength of clay CSEB with tarpaulin curing. 130
5.10 Compressive strength of bricks from laterite CSEB with curing
chamber.
130
5.11 Compressive strength of bricks from clay CSEB with curing
chamber.
131
5.12 Relationship between compressive strength and RHA content. 132
5.13 Relative increase of compressive strength with cement content
for different group of soil.
133
5.14 Water absorption of laterite CSEB with tarpaulin curing. 136
5.15 Water absorption of clay CSEB with tarpaulin curing. 136
5.16 Water absorption of laterite CSEB with curing chamber. 137
5.17 Water absorption of clay CSEB with curing chamber. 137
5.18 Relationship between water absorption and RHA content. 138
5.19 CSEB of control laterite under 5000x magnification. 141
5.20 Schematic view of the interfacial transition zone around an
aggregate particle.
141
5.21 CSEB of control clay under 5000x magnification. 141
xviii
5.22 CSEB of laterite 20% under 5000x magnification. 142
5.23 CSEB of laterite 40% under 5000x magnification. 143
5.24 CSEB of laterite 60% under 5000x magnification. 143
5.25 CSEB of laterite 80% under 5000x magnification. 144
5.26 CSEB of clay 20% under 5000x magnification. 144
5.27 CSEB of clay 20% under 5000x magnification. 145
5.28 CSEB of clay 60% under 5000x magnification. 145
5.29 CSEB of clay 80% under 5000x magnification. 146
5.30 Guideline graph RHA content vs Compressive strength. 156
5.31 Guideline graph RHA content vs Water absorption. 156
xix
LIST OF SYMBOLS AND ABREVIATION
Al2O3 = Aluminium oxide
CaO = Calcium oxide
CO2 = Carbon dioxide
CSEB = Compressed Stabilized Earth Brick
CV = Coefficient of variation
FTIR = Fourier Transform Infra-Red
Fe2O3 = Iron oxide
K2O = Potassium oxide
MgO = Magnesium oxide
Na2O = Sodium oxide
Ω = Electrical resistance (ohm)
OPC = Ordinary Portland Cement
PSD = Particle Size Distribution
R2 = Coefficient of Determinant
RHA = Rice Husk Ash
ρ = Electrical resistivity (ohm.meter)
σ (sigma) = Electrical conductivity {siemens per metre (S/m)}
SiO2 = Silicon dioxide
SO3 = Sulfur trioxide
TGA = Thermogravimetric Analysis
TiO2 = Titanium dioxide
XRD = X-Ray Diffraction
XRF = X-Ray Fluorescence
xx
LIST OF UNITS AND CONVERTION
1 MPa = 1 N/mm2
1 Nm = 1 Joule
1 N = 1 Kg.m/s2
1 sec = 1000 μs
Counts = In terms of EDS – Unit is quantitative element or
chemical characterization.
KeV = Kilo Electron Volts
xxi
LIST OF APPENDICES
APPENDIX TITLE PAGE
A X-Ray Diffraction (XRD) 180
B Amorphous content of RHA 184
C Multiple Linear Regression Analysis for
Laterite Terpaulin Compressive
Strength
188
D Multiple Linear Regression Analysis for
Laterite Curing Chamber Compressive
Strength
190
E
Multiple Linear Regression Analysis for
Clay Terpaulin Compressive Strength
192
F Multiple Linear Regression Analysis for
Clay Curing Chamber Compressive
Strength
194
G Multiple Linear Regression Analysis for
Laterite Terpaulin Water Absorption
196
H Multiple Linear Regression Analysis for
Laterite Curing Chamber Water
Absorption
198
I Multiple Linear Regression Analysis for
Clay Terpaulin Water Absorption
200
J Multiple Linear Regression Analysis for
Clay Curing Chamber Water
Absorption
202
K Table t-Distribution 204
L Research Publication 205
xxii
Book Chapter 205
Conference Proceedings 205
Journals 207
CHAPTER 1
INTRODUCTION
1.1 Background
The oldest earth masonry known is sundried/unfired earth bricks made from shaped
mud brick (adobe) dating back to before 8000-6000 BC and was found in Turkestan,
Russia (Pumpelly, 1908). It was also found in ancient cultures that were scattered from
Assyria (ca. 5000 BC), vaults in the Temple of Ramses II at Gourna, Egypt (3200
years ago), the citadel of Bam in Iran (2500 years old), a fortified city in the Draa
valley in Morocco (2500 years old), the core of the Sun Pyramid in Teotihuacan,
Mexico (300-900 AD), including Great Wall of China (4000 years old) were built from
mud brick (Minke, 2006). Unfired earth with the shape of mud brick (adobe) has been
used since Mesopotamian era but with the invention of fired bricks make unfired
bricks less popular because fired bricks have better strength. However, at the 20th
century, engineers found although unfired bricks not as superior as fired bricks in term
of strength, its properties can be enhanced by compaction (Oti et al., 2009a).
Furthermore, unfired bricks possessed good quality of green and sustainable building
material. Thus, unfired brick that was made with compression process called
Compressed Stabilized Earth Bricks (CSEB) is the modern descendent of adobe brick
from ancient time.
Most of the world populations live in earth material house especially in the hot
arid climate and estimated about one half in developing countries (Minke, 2006). The
use of earth masonry had been once very popular then declined gradually along with
the invention of Portland cement. Although the superiority of cement compare with the
earth masonry seems very appealing, later on people realized the negative impact of
cement to environment. With the increasing awareness of health and environment, it
was realized lately that the use of earth masonry apparently environmentally friendly
2
with such ability to control temperature and humidity of the building makes it an ideal
natural building material (Hall et al., 2012; Minke, 2000).
According to Food and Agriculture Organisation (FAO) of United Nation,
Malaysia produced 2.6 million tons rice in 2014 (FAOstat, 2015). Rice husk will be
used for the fuel in the boiler to generate electricity for the mill and approximately
25% of the husk will be converted to rice husk ash (RHA) (Cook et al., 1977). As a by-
product from rice mill, the utilization of RHA by the people around the rice mill were
very limited that made RHA has very little or no commercial value. Looking at the
statistic, 6.5 million tonnes RHA are available to take advantage of. among the
alternative to utilize the RHA is as a material for CSEB. From the past researches
regarding RHA, mostly used as complimentary material in sustainable construction
(Coutinho, 2003; Tashima et al., 2004). Thus, RHA has big potential as material to
produce low cost and green building material out of it and also will benefit many as it
can be produced locally by indigenous community where the RHA can be found.
CSEB has many basic properties that made it a relatively green building
materials i.e. fire resistant, extremely low embodied energy, hygroscopic (a nature to
absorb moisture) environment regulation, good thermal insulation, ease of
reuse/recycling, vapour permeable wall construction (Sutton et al., 2011) . As earth
masonry, soil is the main ingredient that play important role in CSEB. The soil types
used will affect the selection of correct stabilizer such as ordinary Portland cements
(OPC) that usually used as a primary binder (Bahar et al., 2004; Guettala et al., 2006;
Jayasinghe & Mallawaarachchi, 2009; Oti et al., 2009a; Oti et al., 2009b, 2009c;
Walker, 1995, 1999, 2004; Walker & Stace, 1996), although other binders which
create cementitious effect are often be used as substitution for stabilizer such as lime,
gypsum, pulverized fly ash (PFA) (Freidin & Erell, 1995; Kumar, 2002), ground
granulated blast furnace (GGBS) (Freidin & Erell, 1995; Kumar, 2002; Oti et al.,
2009a; Oti et al., 2009b, 2009c) and many more.
With modern earth building movement is getting more popularity like in
Africa, India and Thailand and start spreading to other country (Chen, 2009; Morris &
Blier, 2004), adobe brick (brick made with sun-dried clay without compaction) and
CSEB making their way to be sustainable yet durable building material, with adobe
brick as the most popular technique. CSEB on the other hand, quite pricey for average
people in developing country since the machinery seems like expensive investment
3
that will only be used once. While in the west, labour’s cost quite pricey (Delgado &
Guerrero, 2006), which is why mechanization is more preferable in practical
sustainability and CSEB is more popular choice. CSEB construction is economically
viable option that can compete with conventional home building methods.
Usually CSEB using Portland cement as stabilizer for it has higher strength.
But the controversy around how high carbon emission contribution caused by cement
production makes CSEB now seems less sustainable. On the other hand, rice husk ash
(RHA) as a by-product from rice milling is an important source of silica and have
confirmed to have pozzolanic properties which means it will create cementitious
materials if finely divided and when combine with calcium hydroxide (Ca(OH)2) at
ordinary temperature with the presence of moisture (Al-Khalaf & Yousif, 1984; Cook
et al., 1977; Hani et al., 2009; Hassan & Mustapha, 2007; Ismail & Waliuddin, 1996;
James & Rao, 1986b; Jauberthie et al., 2000; Jha & Gill, 2006; Laksmono, 2002;
Ramezanianpour et al., 2009; Sensale, 2006; Yalçin & Sevinç, 2001). Furthermore,
pozzolanic materials have filling role that can reduce water demand and increase
cement strength (Coutinho, 2003; Xiaoyu, 1996). As a pozzolan, RHA cannot produce
cementitious material by itself unless it combines with calcium hydroxide. Therefore,
in this project, lime will be used together with uncontrolled burnt RHA to completely
replace cement as a stabilizer.
1.2 Problem Statement
Two third of the world populations which mostly in developing and under developed
countries live in earth material house especially in the hot arid climate (Minke, 2006).
Hence there is a need of cheap, locally available and sustainable construction material
for the housing. Many researches were carried out related to this issue and most of the
researches identified wastes generated locally were used as components for building
material.
Malaysia produced about 2.6 million tonnes rice in 2014 (FAOstat, 2015) and
the wastes is rice husk which is abundantly available in Malaysia. This contributed to
significant amount of RHA waste generated from rice mill. Usually, this RHA waste
causing environmental and disposal problems due to not enough alternatives to use and
take advantage of it (Ramezanianpour et al., 2009). Theoretically, RHA as agricultural
4
waste is suitable as pozzolanic source by virtue of it contains high amount of silica.
(Yalçin & Sevinç, 2001). RHA which contains high percentage of silica, possessed
pozzolanic properties that creates cementitious materials when combine with calcium
hydroxide (Ca(OH)2) solution at ordinary temperature (Sensale, 2006).
Most of the studies used the controlled burnt RHA in the production of
construction materials (Lertsatitthanakorn et al., 2009; Nilantha et al., 2010; Sensale et
al., 2008; Tashima et al., 2004; Zain et al., 2011) rather than utilized the uncontrolled
burnt RHA. Moreover these research works were related to the application of RHA in
concrete production (Chao-Lung et al., 2011; Coutinho, 2003; Tashima et al., 2004;
Xiaoyu, 1996; Zhang et al., 1996) and however its application in brick production was
very limited. Lengthen to these, majority of researches utilized RHA as partial cement
replacement in the concrete mix and few has tried to use RHA in the brick production
but still used as partial cement replacement (Lertsatitthanakorn et al., 2009).
Commonly, most commercial brick is fired brick which contributes to carbon
emission resulted to pollution. As contrast, unfired earth brick is more sustainable as it
uses cement as a binder without need burning in the kiln. Then, if the unfired earth
brick can be made locally with in situ material, more people will have access to
affordable and environmentally friendly building material. Since uncontrolled burnt
RHA is abundantly available and considered as waste from Malaysia rice mill, hence,
this study intended to investigate the potential usage of this uncontrolled burnt RHA as
full cement replacement in the production of CSEB eventhough the uncontrolled burnt
RHA generated from rice milling combustion posesess poor pozzolanic
reactivity(Wansom et al., 2009). The outcome of this study will contribute to the brick
which is cheaper and environmentally friendly production without involving burning
process.
1.3 Aim and Objectives
The aim of this research is to formulate compressed stabilized earth brick (CSEB)
using waste RHA with hydrated lime as full cement replacement as a binder. To
achieve this aim, the following objectives were derived:
i. Investigate the pozzolanicity potential of waste RHA.
5
ii. Explore electrical resistivity method for measuring the pozzolanicity and
comparably assessed the value with electrical conductivity method (Luxan
method).
iii. Determine the optimum CSEB mix proportion.
iv. Examine the effect of curing method with curing chamber and under tarpaulin
sheet.
v. Develop mathematical equation for CSEB compressive strength and water
absorption
1.4 Scope of Study
This study compared the RHA from rice mill that was burnt under uncontrolled
burning condition in the boiler with the RHA under controlled burning in the
laboratory. RHA under controlled burning in the laboratory at first stage used several
temperatures at 400°C, 500°C, 600°C, 700°C, 800°C, 900°C and 1000°C and one
optimal temperature will be chosen to be compared with RHA from rice mill.
The soils used in this study are limited to locally available soil, there are clay
and laterite soil. Among the purpose of this study is to produce cheap and affordable
CSEB. RHA with lime used as a binder in CSEB production. Although hydraulic lime
has better properties than hydrated lime but since hydrated lime that was cheaper than
hydraulic lime, hence this study used the hydrated lime.
Brick dimension used is a scale down size from the average commercial brick
found in the market by halved the common brick size available in the market, which is
from 200 x 100 x 60 mm to 100 x 50 x 30 mm. According to Harrison (2010) this
dimension has the same ratio with the actual size that makes this size feasible to
represent the actual size.
Curing method was done in the open air under the assumption of the average
relative humidity in Malaysia throughout one year that is 80±5%. Curing chamber was
set at temperature 20°C and humidity at 80%. Curing was done for 7, 14 and 28 days
as with the compressive strength and water absorption test.
The result of compressive strength and water absorption test then was analysed
with analysis of variant (ANOVA) to develop mathematical equation and from that
create a simple graph for practical application in producing CSEB.
6
1.5 Thesis Organization
This thesis will comprise the following section.
Chapter 1 introduces the background of research, problems statement, aim and
objectives of the research, scope of work and significance of the study.
Chapter 2 comes up with the literature review on compressed earth brick, history of
bricks, bricks production and elaborate the RHA as a source of silica, pozzolanic
materials, lime reaction with rice husk ash and the findings from previous study.
Chapter 3 explain the methodology used in this study, from the materials preparation,
materials testing, brick production, curing method, and brick testing.
Chapter 4 delivers the information about RHA pozzolanicity in this study from the
aspect of mechanical, physical and chemical properties.
Chapter 5 administers the formulation of CSEB from raw materials, mix proportion,
brick production, curing method, CSEB testing, brick microstructure properties,
relationship between data statistical analysis and mathematical equation model.
Chapter 6 concludes all the work done and provides recommendation for future study.
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
The use of earth masonry can be traced back since before 7500 BC in the shape of
mud brick or adobe with the sun-dried technique. At 4500 BC, trace of fired brick
was found in Indus Valley cities. Circa 500-300 BC, The Greek has had the
knowledge to mix pozzolan with lime mortars in order to make it hydraulic, by
adding highly siliceous, volcanic Santorin earth (Idorn, 1997). However, application
of pozzolan in concrete shows that the Roman is the first to invent hydraulic mortars
as a mixture in concrete around 25 BC in a famous book written by Vitruvius (1932),
De Architectura - Book II. In Chapter VI of the book, he has written “Est etiam
genus pulveris quod efficit naturaliter res admirandas” which means ‘there is also a
kind of powder, which due to its nature gives excellent result’ to the strength and
durability of the concrete. The powder refers to pozzolanic material which turned out
to produce better concrete compared than that of pure lime in aspect of strength and
durability with support of superior workmanship.
However, the superiority of pozzolan in Roman concrete only used during
Roman Empire and slowly faded away along with the collapse of the empire.
Unfortunately, the Roman concrete leave no mix proportion and limitation of
pozzolan source which exclusively available in Rome back then and the decreasing
of workmanship skill were some factors that make Roman concrete forgotten. Hence
the knowledge of this remarkable concrete also disappeared.
With the fall of Roman, earth masonry application still becomes the main
building technique that used across the globe until the invention of Portland cement,
the use of earth masonry started to replace by modern concrete. The cement
production is growing so fast as the economy emerge and concrete now become the
8
most consume material in earth after water (Hewlett, 1998). However, with one third
(Morton, 2008) to one half (Morris & Blier, 2004) of world population still lives in
the low budget earthen architecture mostly in developing country, the use of earth
masonry will regain its popularity once more. And CEB as one of earth masonry
application offers many benefits and superiority than concrete in sustainable and
environmental friendly point of view. Unluckily, mostly commercial CEB in the
market now use cement as stabilizer makes it less green with the issue of carbon
emission.
As the people awareness of the environmental issues increased, the cement
production that releases carbon dioxide in high amount, which in turn creates air
pollution that appear to be hazardous to the human health, has become great concern
among environmentalist. Therefore, the use of earth masonry that incorporated
abundantly available agricultural waste that has pozzolanic properties and lime,
which could absorb CO2 emission in its reverse chemical reaction as stabilizer seems
appealing.
Aside as the additive for cement production, researchers have made attempt
to substitute cement with pozzolan. However, with the natural pozzolan source
restriction, researcher has come out with another source of pozzolan, mostly with by-
product materials from the factory or agriculture.
This recent study worked out in the viewing of making the CSEB without
cement and substituted it with abundantly available RHA and lime especially in the
benefit of cost effectiveness and environmental issues concerning waste materials
disposal and reduction of carbon dioxide emission.
Furthermore, this chapter discussed about multiple materials involved in this
study and conjunction with some literacy those undertaken by previous researchers,
whether research investigation and standards determined by government agency that
had been recognised. So, this research reached alignment between the results of this
research with some methods that have been executed and predefined.
2.2 Compressed Stabilized Earth Brick (CSEB)
Together with rammed earth and adobe, earth brick is one of the oldest building
materials that used widely in the world since the ancient times. CSEB is a modern
9
type of earth brick that manufactured in a mechanical press, made from a mixture of
soil and aggregate (Gesimondo & Postell, 2011). The apparent difference of CSEB
from rammed earth is the process to form it by using compaction with pressure.
Earth brick is always known as ‘green’ material owing to its thermal properties that
‘breathable’. Its thermal properties let the construction to meet the cooling and
heating need of the building. In the winter, earth brick construction will warm up the
building while at the summer, its cooling effect will be very useful.
Earth brick also can be used as exterior and interior wall. Earth brick suitable
as building materials from arid, semi-arid to tropical climate, although in the wet or
rainy climate can make a good use of additional insulation or extended roof
overhangs. Earth brick can be left unfinished or finished with plaster or paint.
However, the natural lime based finished would be better to allow the wall keeps
breathable.
As earth based material, CSEB possessed good sustainability characteristic
in broad range criteria. CSEB considered has low environmental impact as building
material compared to other earth materials such as fired brick. Advantages of CSEB
over fired brick and concrete are:
i. Low embodied energy and carbon emission (Deboucha & Hashim, 2011;
Morton, 2008).
ii. Non-toxic and acid rain free. Firing process in fired brick production would
release, toxic gas and vapours in the firing process from sulphur content of
clay especially sulphur dioxide, fluorides and chlorides (Woolley et al.,
2005).
iii. Fire retardant as earthen walls do not burn (Deboucha & Hashim, 2011).
iv. Good sound insulation (Acosta et al., 2010).
v. Fungi and insect resistant. CSEB house provide constant relative humidity
that prevent fungus forming (Morton, 2008).
vi. Renewable material. With soil as basic material, CSEB can be reused and
reproduced unlike wood or concrete (Morton, 2008).
vii. Energy saving. Owing to the thermal mass properties of CSEB that result in
lower heating and cooling requirements thus lower electricity usage for air
conditioner in the summer and heater in the winter makes it good thermal
10
insulation as CSEB wall absorbs moisture and gives it back when it dries
(Morton, 2008).
viii. Low waste production and easily dispose of with earth as the primary
material (Morton, 2008).
ix. With bamboo or rebar reinforcement, CSEB structures can be built to resist
earthquake damage in seismic zones (Kennedy, 2013).
CSEB has been applied recently in the India and Thailand even though in
small scale project, also some countries in the Africa adopt CSEB system for the
labour cost reason while countries in Europe applied CSEB in the home making
usage more to the environmental reason. Density
2.3 Composition of CSEB
Basically, the development of CSEB involved some materials such as soil, sand, and
water as the main ingredients (matrix), while binder added to enhance the
performance of CSEB. Usually, the binder found in the commercial CSEB is cement,
although some researchers incorporated cementitious materials to substitute cement
for examples lime, lime-RHA, lime-POFA, lime-fly ash, silica fume-coal ash also
can be acted as binders (Basha et al., 2005; Muntohar, 2011; Villamizar et al., 2012).
However, only cement, lime and RHA as binders will be discussed in this study.
2.3.1 Soil
Soil plays very significant role as a natural building material and its availability in
most region of the world is plentiful. Soil is usually obtained directly in the
construction site when excavating foundation or basement is excavated. One of the
key factors to optimize the soil usage as building material is the selection of correct
stabilizer based on the soil used. Therefore, the detail information of the soil used is
essential. Soil is classified based on properties such as grain size, Atterberg’s limit
etc. Also, the type and percentage of clay mineral present in soil very much affect
the binder and strength of the brick.
11
For the production of CSEB, soil can be classified into two categories,
expansive and less expansive soil (Reddy, 2012). Expansive soil is the soil with
excessive swelling clay minerals such as montmorillonite, that when come into
contact with water cause excessive swelling and shrinkage when drying. Expansive
soil best suited with lime stabilizer since lime reacts with expansive clay and form
cementitious hydrates of calcium-silicate, calcium-aluminates that responsible for
strength development. Less expansive soil like kaolinite and illite do not swell and
shrink and best stabilized by cement. In this study, clay and laterite soil will be used
because those are locally available soil in Malaysia.
2.3.1.1 Clay
Clay is formed on the earth's surface as a result of the earth crust weathering for a
very long time of a rock called Feldspar. Feldspar in igneous rocks breaks down to
sedimentary clays mixed with other materials which are blended into clay. This
transformation of rocks turned to be clay is a matter of geology and time where
erosion takes place. The weathering process of clay formation results in a number of
variations in the type of clay.
There are three main groups of clays, there are kaolinite, montmorillonite and
illite (Grim, 2010). These clay types are the result in variations in the particle size of
a particular deposit and/or the quantity of impurities. Clay that was found near the
parent material (granite) called residual or primary clay, usually grainy and has low
plasticity or non-plastic. Clay deposits that were found far away from source
materials, transported by water, wind and ice called sedimentary or secondary clays,
have smaller and more uniform particles, and high plasticity (Velde, 1995). Due to
the weather cycle, the clay will continuously be formed. Figure 2.1 shows the map
from Malaysian Highway Authority of clay distribution in Peninsular Malaysia.
Clay according to soil engineers refers to particles size smaller than
2 µm (Velde, 1995). Based on study about clays in Peninsular Malaysia it was found
out that its specific gravity around 2.42 - 2.65, from XRD test main minerals in clays
is quartz and secondary minerals is kaolinite where from XRF test showed that SiO2
and Al2O3 are the main compounds, and SEM test confirmed the presence of
12
kaolinite and pyrite (Abdullah & Chandra, 1987; Kobayashi et al., 1990; Ting &
Ooi, 1977).
From its plasticity characteristic and properties, clay usually used in
construction material such as fired bricks, adobe, rammed earth for wall and floor
tile. Also clay naturally impermeable to water that makes it suitable for water
construction such as dams (Koçkar et al., 2005). Firing process will change the
physical and chemical properties of clay permanently.
Figure 2.1: Clay distribution map in Peninsular Malaysia
(Source: Malaysian Highway Authority, 1989).
2.3.1.2 Laterite
Laterite literally means brick, derived from the Latin word ‘later’, first introduced by
Francis Buchanan in 1807 (Hamming, 1968; Maignien, 1996; Tardy, 1997) to
describe reddish weathered soil with high concentration of iron and aluminium
oxides and the distinct characteristics of this soil are the presence of an abundance of
sesquioxides and general absence of silica and alkaline earths (Townsend & Reed,
1971).
13
This type of soil commonly found in tropical climate area where there is an
intense chemical weathering and leaching of soluble minerals (Monroe & Wicander,
2009). Upon exposed to continuous weathering, it leads to changes in chemical
compound which resulted in colour changes that indicates the degree of maturity and
due to the various degrees of mostly iron, aluminium oxides, manganese, titanium
hydration where class I is ferric oxide has colour orange to orange yellow, while
class II is red to reddish brown (Posnjak & Merwin, 1919).
According to Tardy (1997), usually the distribution of laterite soil is centred
in the tropic zone from latitude around 23.4378° North to 23.4378° South as shown
in the Figure 2.2. Whereas Gidigasu (1976) had broader criteria for laterite which is
located in tropic and sub tropic area from latitude 35º North and 35º South such as
Australia, Africa and America that is crossed by equator as shown in Figure 2.3.
Figure 2.2: Map of laterite deposit around the world
(source: Petrology of laterite and tropical soil, Yves Tardy, 1997).
In Peninsula Malaysia, laterite was distributed around Melaka, Negeri
Sembilan, Johor, Kedah, Pahang dan Kelantan as shown in Figure 2.4. Laterite
usually found in the hill surface with altitude less than 80 m above the sea level, with
height differences between peak and valley around 20 m, and the slope of the hill
less than 7° and distance between the hill 200-400 m (Newill & Dowling, 1970).
14
Figure 2.3: Distribution of laterite soil in Peninsula, Malaysia
(source: Laterite Soil Engineering: Pedogenesis and Engineering Principles,
M. Gidigasu, 1976).
Traditionally, laterite was used as a building material whether as a mixture in
rammed earth, cob or directly cut into brick since laterite possessed good properties
which can hardly be found in most of the other stone (Persons, 1970). One of its
properties is that laterite does not swell with water hence making it perform well in
packing material especially when there is no sandy condition (Maignien, 1996).
The main composition of laterite constitutes of Iron Oxide (Fe2O3), Silicon
Dioxide, (SiO2) dan Aluminium Oxide (Al2O3) whereas usual compound found in
laterite are Carbon Dioxide (CO2), Calcium Oxide, (CaO), Titanium Dioxide, (TiO2),
Potassium Oxide, (K2O), Sulfur Trioxide, (SO3), Sodium Oxide, (Na2O), and
Magnesium Oxide, (MgO) (Bawa, 1957).
Like clay soil application, laterite also used as contruction material for its
ease to work with in situ. Local soil makes the contructions more sustainable and
cost effective and in the same time environmental friendly most notably in tropical
country (Kasthurba et al., 2015).
15
2.3.2 Stabilizers
Stabilizer for CSEB plays an important role in creating bonding between soil-
stabilizers mixes. In this study, the term stabilizer is also true for binder in as much
as it connects to its role to bind soil and other components of CSEB. One of the main
functions of the stabilizing medium is to reduce the swelling properties of the soil
through forming a rigid framework with the soil mass, enhancing its strength and
durability (Anifowose, 2000).
Portland cement is the most widely used stabilizer for earth stabilization. In
term of cement as a binder, cement hold other material to form a cohesive material
chemically in a more liquid way like in concrete. In term of cement as stabilizer, it
more associated with soil like in brick production and in a drier and bulky way to
enhance its properties mechanically by compacting.
Regarding to brick production, the working of stabilizer depends on its
plasticity index. Many researches (Guettala et al., 2002; Walker, 1995; Walker &
Stace, 1996) found that soil with plasticity index below 15 is suitable for cement
stabilization. Typically, cement binder is added between 4 and 10 % of the soil dry
weight (Mesbah et al., 2004). However, if the content of cement is greater than 10%
then it becomes uneconomical to produce CSEB brick. Brick that using less than 5%
of cement, it often too friable for easy handling (Walker, 1995).
The most popular stabilizers in the brick making are cement and lime.
commercial stabilizers which usually a mixture of chemical binding agents also
getting its way in brick production. Several studies have been done in attempt to
produce green brick incorporating existing stabilizer and additional substance such
as biomass.
16
2.3.2.1 Cement
Cement is used as a stabilizer for CSEB control samples in this study and it
performance will be compared to CSEB with lime as stabilizer. Cement has been
well known as the most popular soil stabilizer (Nagaraja et al., 2014) and many
researchers have observed the role of cement as stabilizer in CSEB (Guillaud et al.,
1995; Kerali, 2001; Venkatarama Reddy & Gupta, 2006; Walker & Stace, 1996).
Cement stabilization increased the unconfined compressive strength of the
soil significantly and in general improvement in mechanical properties is higher
compared to lime stabilization (Asgari et al., 2015). Soil with moderate plasticity
index almost always have higher compressive strength than that of lime stabilizer,
however for soil with high plasticity index, lime stabilizer is more superior
(Bhattacharja & Bhatty, 2003).
Composition of cement mainly known are three components. First the
component that release a lot of heat in the early stage of hydration is Tricalcium
aluminate (Ca3Al2O6) or C3A. The component that responsible of early strength gain
is (Ca3SiO4) or C3S. Belite or dicalcium silicate (Ca2SiO5) or C2S is hydrated and
hardens slowly and responsible for long term strength gain. These three components
will bind the soil in compression with the presence of water.
2.3.2.2 Lime
Not many people aware of the use of lime as binder in concrete preceded the use of
pottery (Kingery, 1980). Even though, many believed that concrete was invented by
the Romans, archaeological evidence showed that concrete was discovered during
Neolithic age (Malinowski & Garfinkel, 1991), long before the Greeks (Koui &
Ftikos, 1998) and Phoenicians (Baronio et al., 1997).
The discovery of binding properties of lime was probably discovered when
Neolithic people that lived in natural cave carved in limestone, used fire to heat or to
cook. It wass not far-fetched to find out the binding properties of lime in the way that
quicklime easily hydrates in the presence of water and hardens in air (Aitcin, 2008).
17
The following table is important as consideration in designing the mix
proportion of the brick. As soil stabilizer, Ingles and Metcalf (1972) recommended
the criteria of lime mixture as shown in Table 2.1 (Ingles & Metcalf, 1972) .
Table 2.1: Suggested lime content (%) in soil stabilization
by Ingles and Metcalf (1972).
Soil Type Lime Content (%)
Fine crushed rock Not recommended
Well graded clay gravels ~ 3 percent
Sands Not recommended
Sandy clay ~ 5 percent
Silty clay 2 – 4 percent
Heavy clay 3 – 8 percent
Very heavy clay 3 – 8 percent
Organic soils Not recommended
Through heating process of calcium carbonate (CaCO3), is released, then in
hydration or slaking process, lime absorbs the water. Until the carbonation process
then, lime will re-absorb the carbon dioxide (CO2) again, this known as lime cycle.
Because the additional chemical content to make lime more hydraulic, the natural
composition of lime will decrease and this will lead to the more hydraulic a lime, the
less CO2 is reabsorbed during set. For example, 50% of CO2 is reabsorbed by
commercial lime product NHL 3.5 during the set, compared to 100% of CO2 being
reabsorbed by pure calcium hydroxide (fat lime putty).
The compressive strength of soil with lime stabilization is more dependent on
time rather than dosage, hence it gains strength with time. Bhattacharja and Bhatty
(2003) suggest that lime stabilized soil also depend on the pozzolanic reaction for
strength gain. The addition of lime to clay is observed can enhance the engineering
properties of the soil such as reducing the plasticity, increase the strength and
Young’s Modulus (Bell, 1996).
18
2.4 Properties of CSEB
The benefit of CSEB in view of sustainability is come from its green properties.
Owned to the compression process, CSEB has better properties compare to the adobe
or mud brick. Followed are the properties of CSEB and its advantages.
2.4.1 Density
Commonly, most researchers found that the density of compressed earth bricks is
within the range of 1500 to 2000 kg/m3. Density of the compressed earth brick is
consistently related to its compressive strength and compactive force applied during
production. The dry density is largely a function of the constituent material’s
characteristics, moisture content during pressing and the degree of compactive load
applied and even in India compressive strength is controlled by density. Types of
compaction applied such as dynamic, static and vibro will also affect the density.
The density of brick can be determined through standard procedure such as ASTM C
140 and BS 1924-2 (1990) and others (Bahar et al., 2004; Morel et al., 2005; Oti et
al., 2009a; Oti et al., 2009c; Walker, 1999). Brick density above 1700 kg/m3 is fire
resistant (Minke, 2006).
2.4.2 Water Absorption and Moisture Content
Water absorption is a function of soil and cement content to absorb and keeping the
water level in accordance with the capacity of these materials. Regarding to brick,
usually water absorption related with the strength and durability of earth bricks and
therefore it is important to determine the rate of water absorption of earth bricks.
Water absorption rate decrease with increasing in age of earth bricks and high rate of
water absorption of a specimen may cause swelling of stabilized clay fraction and
resulting in losing strength with time (Oti et al., 2009c). Water absorption, as well as
porosity, also increases with clay content and decreasing cement content (Taallah et
al., 2014; Walker & Stace, 1996).
Between cement, lime, cement-lime and cement-resin, combination cement
and resin stabilization show the lowest water absorption both in capillary absorption
19
and total absorption. Freidin & Erell (1995) tried to reduce the water uptake by
adding a hydrophobic material, in this case was siloxane-polymethylhydrogen-
siloxane and combined with slag + fly ash which is highly absorbent and the result
showed that the water uptake with the addition of 0.5% siloxane less than a quarter
of the water uptake of fly ash-slag without additive.
Sand content in the mixes apparently can reduce water absorption and weight
loss even though does not affect the compressive strength significantly (Guettala et
al., 2002). Standard used to determine water absorption is ASTM C 140 for total
water absorption, BS EN 771-2 and Australian Standards 2733 for initial rate of
absorption (Oti et al., 2009c; Walker, 1999; Walker & Stace, 1996).
Moisture content affects strength development and durability of the material.
Moisture content also has a significant influence on the long terms performance of
stabilized soil material, especially effect on bonding with mortars at the time of
construction. When the brick is dry, water is rapidly sucked out of the mortar
preventing good adhesion and proper hydration of the cement and when the brick is
very wet the mortars tends to float on the surface without gaining proper adhesion
(Walker, 1999).
Types of compaction also affect the optimum water content in the stabilized
mixes. Dynamic compaction can reduce the optimum water content from 12% to
10% with the compressive strength increased for about 50%. Bahar et al (2004)
stated the optimum water content range between 10 to 13% for static compaction, as
for vibro-static compaction slightly increase compressive strength with the same
water content for low compressive load. According to Osula (1996) soil-lime mixes
required higher optimum moisture content than soil-cement mixes. The Standards
that conform to determine water content such as ASTM D 558, Australian Standards
1289, BS 1924-2 (1990), BS EN 1745:2002 and the newest BS EN 1745:2012.
Generally, the acceptable water absorption is between 12% and 20% for clay
brick. If using engineering bricks the closer to the 12% the better the result will be
but when the water absorption is too low, i.e. below 12%, it may be difficult to
obtain a proper bond between the mortar and the bricks (Vuuren & Cermalab, 2013).
In addition, correspond to moisture content, as earth masonry, CSEB will
absorb more moisture compared with other building materials as shown in the Figure
2.5. According to Morton (2008) earth brick absorb more moisture than other
20
construction materials as shown in Figure 2.4. Also CSEB has the ability to regulate
relative humidity of indoor air in the building which is the key attribute of earth
masonry. The ability of CSEB to absorb and desorb atmospheric moisture comes
from its clay mineral structure.
Figure 2.4: Air moisture absorbed from several materials
(source: Morton, 2008).
2.4.3 Strength
Compressive strength is the most universally accepted value for determining the
quality of bricks. Nevertheless, it intensely related with the soil types and stabilizer
content. Typically, determination of compressive strength in wet condition will give
the weakest strength value. Reduction in compressive strength under saturation
condition can be attributed to the development of pore water pressures and the
liquefaction of unstabilized clay minerals in the brick matrix. Factors affecting the
CSEB brick strength are cement-content, types of soil (plasticity index), compaction
pressure and types of compaction.
Optimum cement content for the stabilization is in the range of 5% to 10%
where addition above 10% will affect the strength of the bricks in negative way.
Plasticity index of the clay soil is usually in the range of 15 to 25. The best earth
soils for stabilization are those with low plasticity index. But for plasticity
index >20, it is not suitable with manual compaction (Walker, 1995). Anifowose
21
(2000) found that irons present in the soil are responsible for low compressive
strength in the soil stabilization process. The strength of the CSEB can be increased
by adding natural fibres where it can improve the ductility in tension. The
improvement is by retarding the tensile crack propagation after initial formation and
also the shrinkage cracking (Mesbah et al., 2004).
Since there is no standard testing for CSEB at the moment, most researchers
determined the compressive strength using the testing method used for fired clay
brick and concrete masonry block such as ASTM 1984, BS 6073-1:1981, BSI 1985,
BS EN 772-1, BS 1924-2:1990, Standard Australia 1997, Australian Standard 2733
(Oti et al., 2009a; Oti et al., 2009c; Walker, 1995, 2004). The unconfined
compressive test needs expensive equipment and must be carried out in the
laboratory, hence some researchers suggest using indirect compressive test (i.e.
flexural test/modulus of rupture/three-point bending test). These indirect test provide
simple, inexpensive and fast assessment of in-situ bending strength of the brick
(Morel & Pkla, 2002; Morel et al., 2005). Walker (1995, 2004) suggested to use
factors that modulus of rupture is equivalent with one-sixth of its compressive
strength and in his latest experiment suggested that unconfined compressive strength
is about five times of the bending strength.
Compacting procedure also affect considerably on the compressive strength
of the CSEB brick. Guettala et al (2002) concluded that by increasing the
compacting stress from 5 to 20 MPa, it will improve the compressive strength up to
70%. His conclusion was strengthened by Bahar et al (2004) observed that by using
dynamic compaction energy dry compressive strength increases by more than 50%
but for vibro-static compaction increases slightly for about 5%.
Because earth structures should not be under tension therefore tensile
strength for earth building materials has no relevance (Minke, 2000).
Brick strength and brick characteristic flexural bond strength are the factors
that limiting the bond strength between bricks and mortars in wall panels made from
CSEB (Walker, 1999). Hence, types of bricks such as solid, interlocking or hollow
and type of bond like English, Flemish or Rat trap bond also play an important role
in flexural strength of the panels (Jayasinghe & Mallawaarachchi, 2009).
22
2.4.4 Durability
The basic principle of stabilization in CSEB is how to attained high mechanical
strength while, at the same time averted moisture intake when exposed to wet
condition. From several experiments, brick’s durability associated with the stabilizer
content, clay content, compacting stress and weather condition. Primarily, durable
stabilized soil material building can be achieved as long as they are not saturated.
The problems arise when the materials are subjected to the long-term saturation and
exposed to various climatic conditions. Also, it is observed that the present of
unstabilized material was likely to be particularly detrimental to the durability.
Heathcote (1995) observed that rain drop can discharge kinetic energy that
impacted the brick and causing material falling from the surface of wall panels. He
stated that wet/oven dry ratio of 33% may be a suitable criterion for evaluating the
durability of cement stabilized earth specimen.
In the tropical climate, soluble salt most commonly sodium sulphate and
sodium chloride can cause salt attack in brick. Salt attack caused cristallization of
salt in the pore structure and in turn will create a pressure that caused rupture in the
material (Bakar et al., 2011). Soluble salt transported to the brick through the
seepage from ground water or near the sea through the air, that can lead to rising
damp and salt attack which in turn can destroy the brick.
As observed by Oti et al (2009b) combination of bricks that made of clay,
cement, lime and Ground Granulated Blast Furnace (GGBS) are subjected up to 100
cycles 24 hours repeated of freezing and thawing showed satisfaction result where
only having maximum 1.9% weight loss at the end of the 100th cycles. This
examination is done after the test showed no damaged occur of any type.
The measurement of durability according to the standards such as ASTM
normalization (ASTAM 1993), ASTM D 599-57 (resistance to water erosion),
ASTM 560 and DDCENT/TS 772-22 (freeze-thaw test), wire brush test, Australian
Standards 2002, Doat, et al. (1979) using water spray test and Yarin, et al (1995)
using water drip test, are very severe compared to the natural condition.
Nevertheless, in general, clay material still have potential to damage from rising
damp, freeze/thaw cycles and surface erosion caused by wind-driven rain as clay
23
mineral tend to disrupt the cement action (Guettala et al., 2002; Oti et al., 2009a; Oti
et al., 2009c; Walker, 1995, 1999, 2004; Walker & Stace, 1996).
2.4.5 Thermal Value
In the growing concern of energy conscious and ecological awareness, thermal
comfort in building materials is an important aspect that attracts great attention since
building regulations nowadays stressing more on the thermal performance of the
buildings compare to the past.
Heat transfer of a building is characterized by its thermal conductivity. As the
building material, earth brick is good thermal conductivity. Oti (2009b) observed
that thermal conductivity is a function of the material density and moisture content.
Thus design value for thermal conductivity can be determined through experimental
and theoretical method. Compressed stabilized earth bricks showed better thermal
conductivity value compare to the fired clay bricks.
• Lime-GGBS based: 0.2545 ± 0.0350 Wm-1 K-1
• Cement-GGBS based: 0.2612 ± 0.0350 W m-1 K-1
• Fired clay bricks: 0.4007 ± 0.0350 W m-1 K-1
The lower the thermal conductivity value of the brick is the better
considering it is directly proportional with the materials thermal mass value. Thermal
mass value is the ability of materials to absorb and gives off heat deliberately after
long period of time. Therefore, if the materials possessed low thermal conductivity
which caused in low thermal mass, then in turn it will result in low energy
consumption that is good in term of sustainable and green materials.
Thermal conductivity can be decreased somewhat low by addition of cement
and sand content (Bahar et al., 2004). Firing process of fired brick caused it has high
thermal conductivity compared to earth brick since the firing process change the clay
particle to form glassy substance and having mineral breakdown and forming
crystalline phase.
The following standards such as BS EN 1745 (thermal conductivity and
thermal resistance), ASTM C 518-91 and ASTM C 1132-89 (thermal value) can be
24
used to determine the thermal value of compressed stabilized earth bricks (Oti et al.,
2009b).
Effect of this thermal conductivity is the indoor temperature. Earth house
temperature will varied by 5°C while concrete house 16°C and at 4 pm the concrete
house 5°C higher than outside temperature while earth house 5°C lower than outside
(Fathy, 1986). The experiment was done in hot arid climate area with two identical
building one was built with 50-cm-thick earth walls when the other of 10-cm-thick
pre-cast concrete.
2.4.6 Carbon Emission and Embodied Energy
A striking contrast between CSEB and conventional fired bricks is the energy
consumed during the production process and carbon emission. CSEB brick creates
22 kg CO2/tonne compared to that of concrete blocks (143 kg CO2/tonne), common
fired clay bricks (200 kg CO2/tonne) and aerated concrete blocks (280 – 375 kg
CO2/tonne) during production as illustrated in Figure 2.5 (Morton, 2008). In average,
cement stabilized earth bricks consumed less than 10% of the input energy as used to
manufacture similar fired clay and concrete masonry unit (Walker, 1995).
Figure 2.5: Values of ‘factory gate’ embodied carbon for masonry materials
(source: Morton, 2008).
The embodied energy is the total amount of energy used in bringing the
material to its present state and location, or in other words as the energy that could
have been save, had the product never been manufactured. Straightforward method
to determine the embodied energy of the masonry may not be available now, but
indirect method can be obtained from Morton (2008) where embodied energy of 146
164
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