CHARACTERISTICS OF COAL ASH MIXTURES AS...

CHARACTERISTICS OF COAL ASH MIXTURES

AS REPLACEMENT MATERIALS IN

GROUND IMPROVEMENT WORKS

ABD. RAHIM BIN HJ. AWANG

UNIVERSITI TEKNOLOGI MALAYSIA

CHARACTERISTICS OF COAL ASH MIXTURES AS REPLACEMENT

MATERIALS IN GROUND IMPROVEMENT WORKS

ABD. RAHIM BIN HJ. AWANG

A thesis submitted in fulfilment of the

requirements for the award of degree of

Doctor of Philosophy (Civil Engineering)

Faculty of Civil Engineering

Universiti Teknologi Malaysia

JULY 2015

iii

To my respectful parents, beloved wife Noraishah Hj. Abdul Rahman

and my children; four Amirul (sons), Ahmad Amirul Asyraf,

Ahmad Amirul Aiman, Ahmad Amirul Afif and Ahmad Amirul Waidz

and three daughters, Ainatul Mahirah, Aina Balthisya and Afrina Raisya Balqis

iv

ACKNOWLEDGMENTS

I would like to deeply praise the Almighty ALLAH SWT for allowing me

passing all of this moment and also I would like to take this opportunity to express

my sincere gratitude to all those who have contributed in completing this project. I

wish to express profound gratitude to my supervisors Prof. Dr. Aminaton Marto and

Assoc. Prof. Dr. Ahmad Mahir Makhtar for their direct supervision, continuous

advice and guidance throughout this research, especially during the writing of this

thesis.

Thanks to all researchers and lecturers in Soft Soil Research Group and the

Department of Geotechnical and Transportation, Faculty of Civil Engineering

(FKA), Universiti Teknologi Malaysia (UTM) who provided helps, valuable

discussions, and cooperation in executing laboratory works. Acknowledgment is

also conveyed to all technicians of Geotechnics laboratory, FKA, UTM; in particular

Mr. Zulkifly Wahid who patiently provided assistance in laboratory tests. Thanks are

also due to lecturers and technicians from Universiti Tun Hussein Onn Malaysia for

their helps in the geochemistry tests. The moral and spiritual supports from all

colleagues in Sultan Haji Ahmad Shah Polytechnic, Kuantan, Pahang are also

acknowledged.

The financial support for this research and scholarship was provided by UTM

and the Ministry of Education, Malaysia. Those are gratefully acknowledged.

Finally, I wish to express special thanks and appreciation to my mother, father and

family for their supports and loves. Special thanks to my wife, Mrs. Noraishah Abdul

Rahman, for her loves, sacrifices, patience, and continuous struggle towards the

accomplishment of this study.

v

ABSTRACT

Fly ash (FA) and bottom ash (BA) are two of the coal ashes by-products

produced from coal-fired power plants. They are usually disposed off together as a

waste in utility disposal sites with a typical disposal rate of 80% FA and 20% BA.

The use of coal ash in construction projects that require large volume materials, such

as in soil improvement works, is highly promising in solving the disposal problem.

The aim of this research is to determine the suitability of FA-BA mixtures as

replacement materials for soft soil foundation. Representative samples of coal ash

were collected from Tanjung Bin Power Plant, Pontian, Johor. Six mixtures of FA

and BA with different mix ratios of 0%, 30%, 50%, 70%, 90% and 100% FA content

by weight had been used in this study. The coal ash mixtures were compacted at 95%

of maximum dry density, sealed and cured for 0, 14, and 28 days before being

analysed for material characterization, mechanical properties and chemical analysis.

The performance of FA-BA mixtures as replacement materials had been determined

through laboratory physical model tests. In model test, 40 cm height (H) of soft

kaolin clay (about 20 kPa undrained strength) was replaced fully and partially by FA-

BA mixtures (Hm) at replacement ratio, Hm/H = 0, 0.125, 0.375 and 1.0. In general,

the results of the laboratory tests indicate good performance of FA-BA mixtures.

Morphological analysis shows that the number of irregular shaped particles increased

confirming change in material type with curing period. The results also show that

mixtures with higher fly ash composition have less drainage characteristics but can

be improved by prolonging the curing period. The shear strength of coal ash mixtures

varied depending on the FA content. The maximum shear strength was obtained at

the mixture of 50%FA with the friction angle values ranged from 270 to 37

0 that

increased with curing period. The California Bearing Ratio (CBR) values increased

while compressibility decreased with curing periods due to pozzolanic reaction. CBR

values and compressibility of the mixtures also generally decreased with the

increased of FA content. Results suggest that ash mixtures are non-corrosive while

the heavy metals concentration is below the limit set by respective authority. Since

the mixture of 50%FA-50%BA has the highest strength and considerably low

compressibility, it can be concluded that this mixture is the most suitable mixture for

replacement of soft soil. The result of physical model tests concluded the suitability

of FA-BA mixtures as full or partial replacement materials of soft clay that gives

promising effect in terms of decreasing the settlement of the footing placed on top of

the soil. Based on this, preliminary design charts had been developed for the usage of

FA-BA mixtures in geotechnical engineering works. This could help the engineers

not only in designing the depth of soil to be replaced in soil improvement works but

also in other purposes that rely on the strength of the eco-friendly ash mixtures.

vi

ABSTRAK

Abu terbang (FA) dan abu bawah (BA) adalah dua daripada keluaran

sampingan yang terhasil daripada loji tenaga arang batu. Bahan ini biasanya

dilupuskan bersama sebagai bahan buangan di tapak pelupusan utiliti dengan kadar

pelupusan 80%FA dan 20%BA. Penggunaan abu arang batu dalam projek-projek

pembinaan yang memerlukan bahan yang banyak seperti dalam kerja-kerja

pembaikan tanah, adalah sangat memberangsangkan dalam menyelesaikan masalah

pelupusan. Tujuan kajian ini adalah untuk menentukan kesesuaian campuran FA-BA

sebagai bahan gantian untuk tanah asas yang lembut. Sampel abu arang batu telah

dikumpulkan dari loji janakuasa Tanjung Bin, Pontian, Johor. Enam campuran FA

dan BA dengan nisbah campuran yang berbeza; 0%, 30%, 50%, 70%, 90% dan

100% kandungan FA mengikut berat telah digunakan dalam kajian ini. Campuran

abu arang batu telah dipadatkan pada 95% ketumpatan kering maksimum, dibalut

dan diawet kepada tempoh masa 0, 14, dan 28 hari sebelum dianalisis untuk

pencirian bahan, sifat mekanik dan analisis kimia. Prestasi campuran FA-BA sebagai

bahan gantian telah ditentukan melalui ujian model fizikal makmal. Dalam ujian

model, 40 cm (H) ketinggian tanah liat kaolin lembut (kira-kira 20 kPa kekuatan tak

tersalir) telah digantikan sepenuhnya dan sebahagiannya oleh campuran FA-BA (Hm)

pada nisbah penggantian, Hm/H = 0, 0.125, 0.375 dan 1.0. Secara umum, keputusan

ujian makmal menunjukkan campuran FA-BA berprestasi baik. Analisis morfologi

menunjukkan bahawa bilangan zarah berbentuk tidak teratur meningkat

mengesahkan perubahan jenis bahan dengan tempoh pengawetan. Keputusan juga

menunjukkan bahawa campuran dengan komposisi abu terbang yang lebih tinggi

mempunyai ciri-ciri saliran yang lebih rendah tetapi boleh ditingkatkan dengan

memanjangkan tempoh pengawetan. Kekuatan ricih campuran abu arang batu

berubah bergantung kepada kandungan FA. Kekuatan ricih maksimum adalah pada

campuran 50%FA dengan nilai sudut geseran antara 270-37

0 yang meningkat dengan

tempoh awetan. Nilai Nisbah Menggalas California (CBR) meningkat manakala

kebolehmampatan menurun dengan tempuh awetan disebabkan oleh tindak balas

pozzolanik. Nilai CBR dan kebolehmampatan daripada campuran juga umumnya

menurun dengan peningkatan kandungan FA. Keputusan menunjukkan bahawa

campuran abu adalah tidak menghakis manakala kepekatan logam berat adalah di

bawah had yang ditetapkan oleh pihak berkuasa. Disebabkan campuran

50%FA-50%BA mempunyai kekuatan tertinggi dan kebolehmampatan agak rendah,

ia boleh disimpulkan bahawa campuran ini adalah campuran yang paling sesuai

untuk menggantikan tanah lembut. Hasil ujian model fizikal menyimpulkan

kesesuaian campuran FA-BA sebagai bahan gantian tanah liat lembut secara penuh

atau sebahagian yang memberikan kesan baik dari segi mengurangkan enapan asas

yang diletakkan di atas tanah. Berdasarkan ini, carta reka bentuk awal telah

dibangunkan untuk penggunaan campuran FA-BA dalam kerja-kerja kejuruteraan

geoteknik. Ini boleh membantu jurutera bukan sahaja untuk pemilihan kedalaman

tanah yang akan digantikan dalam kerja-kerja pembaikan tanah tetapi juga untuk

tujuan lain yang bergamttung kepada kekuatan campuran abu yang mesra alam.

vii

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES xiv

LIST OF FIGURES xix

LIST OF ABBREVIATIONS xxvi

LIST OF SYMBOLS xxviii

LIST OF APPENDICES xxxi

1 INTRODUCTION 1

1.1 Background of Research 1

1.2 Problem Statement 5

1.3 Objectives of Research 6

1.4 Scope of Research 7

1.5 Significance of Research 7

1.6 Thesis Organisation 8

2 LITERATURE REVIEW 10

2.1 Introduction 10

2.2 Coal Fired Power Plant in Malaysia 13

2.3 Coal Combustion Products 16

2.3.1 Introduction 16

2.3.2 Fly Ash 20

viii

2.3.2.1 Class C fly ash 21

2.3.2.2 Class F fly ash 21

2.3.3 Bottom Ash 22

2.4 Physical Properties of Coal Ash 23

2.4.1 Appearance and Shape 23

2.4.2 Specific Gravity 26

2.4.3 Particle Size Distribution 28

2.5 Mechanical Properties of Coal Ash 32

2.5.1 Compaction Behaviour 32

2.5.2 Permeability (Hydraulic Conductivity) 36

2.5.3 Strength 39

2.5.3.1 Shear Strength Parameter 39

2.5.3.2 California Bearing Ratio 44

2.5.4 Compressibility 45

2.6 Morphological, Mineralogical, Pozzolanic

Activity and leachate Properties 48

2.6.1 Microscopic Examination of Particles 48

2.6.2 Mineral Composition 51

2.6.3 Chemical Analysis 53

2.6.4 Pozzolanic Activity 55

2.6.5 Heavy Metal and Corrosivity of Coal Ash 56

2.7 Properties of Coal Ash Mixtures 60


2.7.2 Compaction Characteristics 63

2.7.3 Permeability 65

2.7.4 Strength and Compressibility 66

2.8 Utilisation of Coal Ash in Geotechnical

Engineering Work 67

2.9 Environmental Aspects of Coal Ash Usage

in Geotechnical Engineering Work 70

2.10 Soft Clay Problems 71

2.10.1 Introduction 71

2.10.2 Bearing Capacity 72

2.10.3 Consolidation Settlement 74

ix

2.10.4 Properties of Soft Clay 74

2.11 Physical Modelling of Embankment 78

2.11.1 Full-Scale Tests of Embankment on Soft Soil 78

2.11.2 Full-Scale Test of Embankment using Fly Ash

as Backfill Materials 80

2.11.3 Laboratory Physical Model Test 82

2.11.3.1 Introduction 82

2.11.3.2 Development of Dimension Model 82

2.12 Summary 85

3 RESEARCH METHODOLOGY 86

3.1 Introduction 86

3.2 Research Activities 87

3.2.1 Research Design 87

3.2.2 Literature Search and Information Collection 89

3.2.3 Sample Collection and Preparation 89

3.2.3.1 Sample Collection 89

3.2.3.2 Preparation of Fly Ash and Bottom Ash

Samples 91

3.2.3.3 Preparation of FA-BA Mixtures 91

3.2.3.4 Curing of the Samples 93

3.2.4 Equipment Preparation and Calibration 93

3.3 Sample Characterisation and Properties Establishment 95

3.3.1 Laboratory Testing Programme 95

3.3.2 Physical Tests 98

3.3.2.1 Specific Gravity 98

3.3.2.2 Sieve Test 99

3.3.2.3 Hydrometer Test 100

3.3.2.4 Atterberg Limit Test 102

3.3.3 Material Characterisation and Geochemistry Tests 103

3.3.3.1 Morphology Characteristics 103

3.3.3.2 Mineralogy Characteristics 104

3.3.3.3 Element Characteristics 105

x

3.3.3.4 Thermal Analysis 106

3.3.3.5 Heavy Metal Study 107

3.3.3.6 pH Test 109

3.3.4 Mechanical Tests 109

3.3.4.1 Direct Shear Test 109


3.3.4.3 Permeability Test 112

3.3.4.4 Consolidation Test 115

3.3.4.5 Unconfined Compression Test 116

3.5 Analysis of Data 118

3.6 Determination of Settlement of FA-BA Mixtures as

Soft Clay Replacement 118

3.6.1 Laboratory Physical Model 118

3.6.1.1 Introduction 118

3.6.1.2 Model Size and Design 119

3.6.2 Size of Test Box Model 121

3.6.2.1 Considering Soft Clay, ɸ = 34.030 122

3.6.2.2 Considering the Strongest FA-BA

Mixtures, ɸ = 36.850 123

3.6.3 Fabrication of Model Test Box 124

3.6.4 Loading Frame for Soft Soil Preparation 125

3.6.5 Load Testing Assembly for Settlement 127

3.6.6 Testing Programme for Model Tests 129

3.6.7 Preparation of Sample 130

3.6.7.1 Soft Clay Preparation 130

3.6.7.2 Preparation of Full FA-BA Mixture Layer 132

3.6.7.3 Preparation of Partially Replaced Soft Clay

with FA-BA Mixtures Layer 134

3.6.8 Settlement Test & Monitoring 134

3.6.9 Anaysis of Settlement Test Results 135

xi

4 PHYSICAL, MORPHOLOGICAL, MINERALOGY

AND MECHANICAL CHARACTERISTICS

OF FA-BA MIXTURES 136

4.1 Introduction 136

4.2 Physical Characteristics 137

4.2.1 Specific Gravity 137

4.2.1.1 FA-BA Mixtures 137

4.2.1.2 Kaolin 139


4.3 Morphology Characteristics 141

4.4 Mineralogy Characteristics 153

4.5 Mechanical Characteristics 155

4.5.1 Compaction 155

4.5.2 Permeability 159

4.5.3 Strength Behaviour 163

4.5.3.1 Unconfined Compression Strength 163

4.5.3.2 Direct Shear of FA-BA Mixtures 168

4.5.3.3 Direct Shear of Kaolin 175

4.5.3.4 Undrained Strength of Kaolin 176


4.5.4 Compressibility of FA-BA Mixtures 181

5 CHEMICAL, POZZOLANIC ACTIVITY, CORROSIVITY

AND HEAVY METAL CHARACTERISTICS

OF FA-BA MIXTURES 189


5.2 Chemical Characteristic 189

5.3 Thermal Gravimetri Analysis 196

5.4 pH Characteristics 199

5.5 Heavy Metal Content 201

xii

6 SETTLEMENT OF SOFT CLAY REPLACED BY

FULLY AND PARTIALLY FA-BA MIXTURES 204


6.2 Properties of Compacted Soft Clay and FA-BA Mixtures 205

6.3 Settlement Results of Model Tests 206

6.3.1 Full Replacement 207

6.3.1.1 Time-Settlement Behaviour 207

6.3.1.2 Effect of FA Content 210

6.3.2 Partial Replacement 214

6.3.2.1 Time-Settlement Behaviour 214

6.3.2.2 Effect of Replacement Height Ratio 217

7 DESIGN CHARTS FOR APPLICATION OF COAL ASH

MIXTURES AS ALTERNATIVE MATERIALS IN

GEOTECHNICAL ENGINEERING WORKS 221


7.2 Recommendations for the Selection of Design Parameters 222

7.2.1 Environmental Aspects 223

7.2.2 Design Aspects 224

7.2.3 Construction Aspects 225

7.3 Proposed Design Chart for FA-BA Mixtures as

Replacement Materials 225

7.3.1 Unconfined Compressive Strength versus Fly Ash

Content Charts 226

7.3.2 Settlement Chart for FA-BA Mixtures in

Full Soil Replacement 232

7.3.3 Settlement Chart for Partially Replaced Soft Clay

by FA-BA Mixtures 234

8 CONCLUSION AND RECOMMENDATIONS 236


8.2 Conclusion 237

8.3 Contribution of Research 239

xiii

8.3.1 Ground Improvement 239

8.3.2 Sustainability 239

8.3.3 Economy 240

8.3.4 Originality 240

8.4 Recommendations for Future Research 241

REFERENCES 242

Appendices A-N 248-350

xiv

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Total energy supply and coal consumption in some

countries in 2003 (Fujitomi and Matsui, 2005) 11

2.2 Generation mix by fuel kind (Energy Commission Malaysia, 2005) 12

2.3 List of Coal-Fired Power Stations in Malaysia up to year 2010

(Jaffar, 2009) 14

2.4 Coal demand estimations for year 2010 to 2030 (based on Year

2005) (Ghazali, 2007) 15

2.5 Worldwide FA production (Geertsema, 2007) 19

2.6 Chemical content of class C pulverised fly ash

(ASTM C 618, 2004) 21

2.7 Chemical content of PFA class F (ASTM C 618, 2004) 22

2.8 Specific gravity and chemical composition of FA and BA

from the Wabash River Plant, USA (Kim et al., 2005a) 27

2.9 Typical specific gravity for different origins of Fly Ash 28

(Muhardi et al. 2010)

2.10 Permeability of Indian FA (Pandian, 2004) 36

2.11 Permeability of Indiana FA (Kim, 2003) 37

2.12 Permeability of the Wabash River Plant ash mixtures

(Kim et al., 2005a) 37

2.13 Hydraulic conductivity of typical soils (Terzaghi et al. 1996) 38

2.14 Results of direct shear tests on Indiana Bottom Ashes

(Huang, 1990) 40

2.15 Results of peak friction angle of Indiana FA from direct shear test

(Kim, 2003) 41

2.16 Results of cohesion of Indiana FA from direct shear test

(Kim, 2003) 41

xv

2.17 Results of strength parameters under different test

conditions of FA from India (Pandian, 2004) 42

2.18 Peak shear strength parameters taken from direct shear tests

for different age specimens (Tri Utomo, 1996) 42

2.19 Residual strength parameters taken from direct shear test on

FA at different age specimens (Tri Utomo, 1996) 43

2.20 Peak and residual strength parameters taken from consolidated

drained triaxial on FA at different age specimens

(Tri Utomo, 1996) 43

2.21 CBR values according to Road Note 29

(TRRL Laboratory Report 1132) 44

2.22 Results of compression index for Indian FA (Pandian, 2004) 46

2.23 Results of coefficient of volume change, mv (cm2/kg)

for Indian FA (Pandian, 2004) 47

2.24 Results of coefficient of consolidation, Cv (10-3

/kg)

for Indian FA (Pandian, 2004) 47

2.25 Results of compression index at different placement

conditions for Indian FA (Pandian, 2004) 48

2.26 Mineralogy of the coal fly ash from the AE

power plant (Suphi, 2005) 52

2.27 Mineral content in Candiota coal (Marcal et al., 2004) 52

2.28 Typical range of analysis from UK fly ash (Reed, 2005) 54

2.29 Chemical analysis of coal ash (Huang, 1990) 55

2.30 Indiana Administrative Code restricted wasted site type

criteria Indiana Administrative Code, 329 IAC 2-9-3 (IAC 1993) 58

2.31 Compaction properties of ash mixtures (Kim, 2003) 64

2.32 Permeability of Wabash River Plant ash mixtures

(Kim et al., 2005a) 65

2.33 Uses of Coal Combustion Products in Highway Applications

(GAI and USIFCAU, 1993) 67

2.34 Utilization of coal ash and quantities used in each area during

2001 in the USA in thousand tons (Kim, 2003) 68

2.35 Utilization of Fly ash and quantities used in Europe for each area

in 1999 (Meij and Berg, 2001) 69

xvi

2.36 Utilization of Fly ash and quantities used in each area in 1997

in UK (Sear, 2001) 69

2.37 Comparison of index properties of clay in different places

(Jamal et al., 1997) 75

2.38 Classification properties of clay soil from

West Coast of Peninsular Malaysia 76

2.39 Typical value of compression index of different type

of soil (GEO5 user‟s guide, 2010) 77

2.40 Properties of kaolin used by previous researchers 78

2.41 Comparison of Delaware and Pennsylvania full scale FA

embankment (after Yoon et al., 2009, Golden and

DiGioia, 2003 and Ki, 2003) 81

3.1 List of major equipments 94

3.2 Laboratory tests and standard/method used 97

3.3 Laboratory testing programme for FA-BA mixtures 98

3.4 Laboratory model settlement programme 130

4.1 The value of specific gravity of coal ash mixtures 137

4.2 The comparison of specific gravity and iron oxide

of FA-BA mixtures 139

4.3 Basic grain size indices and the classification of

FA-BA mixtures from Unified Soil Classification

System (USCS) 141

4.4 Summary of mineral composition of coal ash mixtures 155

4.5 Standard proctor compaction test results for coal ash mixtures 156

4.6 Coefficient of permeability, k of various mixtures

at different curing periods

159

4.7 Unconfined compression strength of FA-BA mixtures at

various curing period 164

4.8 Normal stress and peak stress obtained from direct shear

tests on FA-BA mixtures at various curing periods 170

4.9 Shear strength parameters from direct shear test for

FA-BA mixtures at various curing periods 171

4.10 Shear strength of FA-BA mixtures at normal stress

xvii

of 50 kN/m2

at various curing periods 174

4.11 Direct shear test result of soft kaolin 176

4.12 Undrained shear strength results from vane

shear tests on reconstituted soft kaolin 177

4.13 Variation of CBR values with FA content and curing periods 178

4.14 Shear strength of FA-BA mixtures at various

normal stress (28 day curing period) 180

4.15 Summary result on compressibility characteristics

of FA-BA mixtures 183

5.1 Chemical content of ash at pure condition (0 days)

curing time 190


curing time 190


curing time 191

5.4 Chemical content of Tanjung Bin fly ash and bottom ash

at pure condition (0 day) 191





5.7 Mass loss of Ca(OH)2 (at 5000C to 600)

0C) for ash mixtures 197

5.8 pH value of FA-BA mixtures 199

5.9 AAS test results at 0 day curing period 202

5.10 AAS test result at 14 day curing period 202

5.11 AAS test result at 28 day curing period 202

6.1 Properties of reconstituted soft clay (kaolin) 205

6.2 Properties of compacted FA-BA mixtures 206

6.3 Settlement of soft clay layer and the layer of FA-BA

mixtures at 3, 7, 14, and 28 days after loading 208

6.4 Settlement at day 28 of soft clay layer and

the layer of FA-BA mixtures 209

6.5 Values of constant A, B and C from

Equation 6.1, obtained from Fig. 6.2 211

xviii

6.6 Regression equations of A, B and C with

coefficient of determination, R2 212

6.7 Settlement of partially replaced soft clay with 50%FA–50%BA

mixtures at 3,7,14 and 28 day of loading 216

6.8 Settlement at day 28 of soft clay layer and the layer of FA-BA217

6.9 Values of constants c and m from Equation 6.3 218

6.10 Regression equation of c and m with coefficient

of determination, R2 219

7.1 Values of constant c and m from Equations 7.1 and 7.2 227

7.2 Regression equations of c and m with coefficient

of determination, R2 229

xix

LIST OF FIGURES

FIGURE NO. TITLE

PAGE

1.1 Location of coal fired power plants in

Peninsular Malaysia (Mahmud, 2008) 2

2.1 Energy input in power stations for (a) Year 1998 and (b) Year

2005 (Ghazali, 2007) 12

2.2 Coal-fired power stations in Malaysia (Jaffar, 2009) 14

2.3 Tanjung Bin Coal-Fired Power Plant, Johor

(Muhardi et al., 2010) 16

2.4 Schematic diagram of a coal fired power station

(Meij and Berg, 2001) 17

2.5 Schematic diagram of coal ash generation (FHWA, 2002) 18

2.6 Production of coal ash in the USA (Kim, 2003) 19

2.7 Fly ash and bottom ash collected from coal-fired power plant

(Muhardi, 2010) 20

2.8 Fly Ash particles at 2000x magnification (American Coal Ash

Association, 2003) 23

2.9 Particle shape of the bottom ash (Chen et al., 2008) 24

2.10 Coal ashes as by-products of coal burning

(a) Fly ash (b) Bottom ash (Kim et al., 2005a) 24

2.11 Typical gradation ranges of coal ash (Kim, 2003) 29

2.12 Grain size distributions of bottom ash and fly ash (Lee, 2008) 30

2.13 Grain distributions for each FA, BA and coal ash

mixtures (Kim et al., 2005b) 31

2.14 Compaction curves of ash mixtures (Kim et al., 2005b) 32

2.15 Typical compaction curves for Western Pennsylvania bituminous

FA (Kim, 2003) 33

2.16 Typical compaction curves for Western United States lignite and

xx

sub bituminous FA (Kim, 2003) 34

2.17 Dry density and water content relation for Indian fly ash and soils

(Pandian, 2004) 35

2.18 Hydraulic conductivity versus FA content from Wabash

River Plant (Kim et. al., 2005b) 38

2.19 CBR value with different proportions of fly ash with different

kinds of soil (Sahu, 2001) 45

2.20 SEM photographs of fly ash and bottom ash

(Ctvrtnickova et al., 2010) 49

2.21 Scanning electron microscope (SEM) photomicrographs of

bottom ash (a) pure specimen and (b) 28 days compacted

specimen (Lee, 2008) 50

2.22 Particle size distributions of the Wabash River Plant fly ash,

bottom ash, and fly-bottom ash mixtures (Yoon, 2005) 62

2.23 Particle size distributions of the A.B.Brown Plant fly ash,

bottom ash, and fly-bottom ash mixtures (Yoon, 2005) 62

2.24 Compaction curves of fly ash and bottom ash mixtures from

the Wabash River Plant (Kim, 2003) 63

2.25 Compaction curves of fly ash and bottom ash mixtures from

the A.B.Brown Plant (Kim, 2005) 64

2.26 Hydraulic conductivity againt FA content of FA-BA

mixtures of coal ash from from Wabash River Plant

(Kim et al., 2005b) 66

2.27 Failure modes of shallow foundation (redrawn

after Vesic (1973) by Das, 2004) 72

2.28 Failure mechanism from general shear failure of

shallow foundation (Sutjiono and Najoan, 2005) 83

3.1 Flowchart of research activities 88

3.2 Tanjung Bin coal-fired power station Pontian, Johor 90

3.3 Supplied kaolin in bags, stored at a dry place in the laboratory 90

3.4 Apparatus for standard proctor compaction test 92

3.5 Curing of FA-BA mixtures sample 93

3.6 Portable data logger type UCAM-70A 95

3.7 Pycnometer test apparatus 99

xxi

3.8 Sieve tests apparatus 100

3.9 Hydrometer test apparatus 101

3.10 ZEISS SUPRA 35-VP scanning electron microscope 103

3.11 X-ray diffractometer of type Siemens Diffraktometer D5000 105

3.12 X-ray fluorescence of type Bruker AXS Model S4 Pioneer

chemical element of sample 106

3.13 TGA/SDTA 851 Model (METTLER TOLEDO) 107

3.14 TRACE AI1300-AAS model 108

3.15 pH meter test equipment 109

3.16 Direct shear test equipment 111

3.17 California bearing ratio (CBR) test equipment 112

3.18 Falling head permeability equipment 113

3.19 Schematic diagram of constant head permeability test 115

3.20 Oedometer consolidation test equipment 116

3.21 Unconfined compression test apparatus 117

3.22 Schematic diagram of laboratory settlement model test 119

3.23 Sectional view of the test models series for (a) Double layer

(b) Single layer (FA-BA mixtures) (c) Single layer (soft clay) 121

3.24 Details of loading plate and model test box 125

3.25 Schematic diagram of loading frame for preparation of

homogeneous soft kaolin clay soil 126

3.26 Schematic diagram of loading frame for consolidation tests 128

3.27 Details of load connection frame 128

3.28 Dimension of loading plate model (strip footing) 129

3.29 Location of vane shear tests on the reconstituted soft clay soils 131

3.30 Preparation of homogeneous soft clay by consolidation process 132

3.31 Mixing of FA-BA mixtures in concrete mixer machine 133

3.32 Completed compacted FA-BA mixture in test box model 133

3.33 Settlement test on prepared soft clay model 135

4.1 Specific gravity at different FA composition 138

4.2 Grain size distribution of coal ash mixtures 140

4.3 SEM micrograph of coal ash mixtures particles (0 day)

(Magnification ×1000), (a) 0%FA; (b) 30%FA;

(c) 50%FA; (d) 70%FA; (e) 90%FA; (f) 100%FA 144

xxii

4.4 SEM micrograph of coal ash mixtures particles (14 days)

(Magnification ×1000), (a) 0%FA; (b) 30%FA; (c) 50%FA;

(d) 70%FA; (e) 90%FA; (f) 100%FA 145

4.5 SEM micrograph of coal ash mixtures particles (28 days)

(Magnification ×1000), (a) 0%FA; (b) 30%FA; (c) 50%FA;

(d) 70%FA; (e) 90%FA; (f) 100%FA 146

4.6 SEM micrograph of coal ash mixtures particles (0%FA)

(Magnification ×1000), (a) 0 day; (b) 14 day; (c) 28 day 147











4.12 Crystalline compounds at 50% FA-BA mixtures from XRD

Difractograms 154

4.13 Dry unit weight at various coal ash mixtures 157

4.14 Optimum moisture content at various coal ash mixtures 157

4.15 Coefficient of permeability coal ash mixtures

at various curing periods 160

4.16 Coefficient of permeability coal ash mixtures at various

fly ash composition 161

4.17 Variation of compressive strength of FA-BA mixtures with

FA contents for different curing periods 164

4.18 Variation of unconfined compressive strength of FA-BA

mixtures with curing periods for different fly ash content 165

4.19 Bar chart on increased in unconfined compressive strength

at different intervals of curing periods for various fly ash

content in FA-BA mixtures 166

4.20 Shear stress versus horizontal displacement from direct shear

xxiii

tests for 50%FA-50%BA mixtures at different normal stress 169

4.21 Peak friction angle of coal ash mixtures at various FA content 172

4.22 Cohesion intercept of coal ash mixtures at various FA content 173

4.23 Peak friction angle of coal ash mixtures at various curing time 173

4.24 Cohesion intercept of coal ash mixtures at various curing time 174

4.25 Shear strength of coal ash mixtures at various FA content 175

4.26 Shear strength of coal ash mixtures at various curing time 175

4.27 Variation of CBR values with curing periods at different

FA content 179

4.28 Variations of CBR values with FA contents at different

curing periods 179

4.29 Shear strength of FA-BA mixtures at various percentages

of FA at 28 day curing periods 181

4.30 A typical settlement versus square root time curve at 70%FA,

28 day curing period 182

4.31 A typical e-log graph for 70%FA mixture at

28 day curing period 182

4.32 Relationship between coefficient of consolidation with FA

contents and the variation with curing periods for all mixtures 184

4.33 Coefficient of consolidation versus pressure at different phase in

consolidation test for 70%FA mixture at 28 day curing period 184

4.34 Changes of coefficient of volume compressibility

with curing periods 185

4.35 Variation of compression index and swelling index

with curing time 187

5.1 CaO content at various fly ash compositions at difference

curing period 193

5.2 Effect of curing period on the Al2O3 composition at

different FA-BA mixtures 193

5.3 Effect of curing periods on the SiO2 composition at

different FA-BA mixtures 194

5.4 SiO2 content at various fly ash compositions at different

curing period 194

5.5 Percentage of Chemical Content at 50% fly ash 195

xxiv

5.6 Mass loss of Ca(OH)2 for FA-BA mixtures at various

curing periods 197

5.7 Effect of FA compositions on mass loss of Ca(OH)2 at

0, 14 and 28 day curing periods 198

5.8 pH value of FA-BA mixtures at different curing period 199

5.9 Arsenic value of FA-BA mixtures at different curing period 202

5.10 Cadmium value of FA-BA mixtures at different curing period 202

6.1 Time-settlement relationship of soft clay layer and layer

of FA-BA mixtures at various FA compositions 208

6.2 Relationship between settlement of layers of FA-BA mixtures

and FA content at various loading time 211

6.3 Correlation between constant A and time 211

6.4 Correlation between constant B and time 212

6.5 Correlation between constant C and time 212

6.6 Correlation of settlement with FA content at various

loading time 213

6.7 Time-settlement relationship of footing on 50%FA-50%BA

mixtures at various replacement height ratio 215

6.8 Effect of partial replacement of soft clay on the settlement with

layer of 50%FA-50%BA mixtures at various loading time 218

6.9 Correlations of constants c and m with time of loading 219

6.10 Correlation of settlement with height replacement ratio

at various loading time 220

7.1 Relationship between unconfined compressive strength and

FA content at various loading time for FA>50% 227

7.2 Relationship between unconfined compressive strength and

FA content at various loading time for FA<50% 227

7.3 Correlation of constant c with loading time at (a) FA> 50%

and (b) FA< 50% 228

7.4 Correlation of constant m with loading time at (a) FA> 50%

and (b) FA< 50% 229

7.5 Correlation of unconfined compressive strength with

FA content at various loading time for FA > 50% 231

7.6 Correlation of unconfined compressive strength with

xxv

FA content at various loading time for FA < 50% 231

7.7 Design charts (UCT-Ash Mixtures) of unconfined

compressive strength for FA-BA mixtures 232

7.8 Design chart (Settlement-FRAM) of settlement for

FA-BA mixtures in full Soil replacement 233

7.9 Design charts (Settlement-PR50FA) of settlement for

50%FA-50%BA mixtures in partial replacement of

soil with Su = 20 kPa and vertical stress = 216 kPa 234

xxvi

LIST OF ABBREVIATIONS

AAS - Atomic absorption spectroscopy

ACAA - American Coal Ash Association

ASTM - American Society of Testing Material

BA - Bottom ash

BS - British standard

CCP - Coal combustion product

CD - Consolidated drained

CU - Consolidated undrained

FA - Fly ash

FA-BA - Fly ash – bottom ash

FBA - Furnace bottom ash

FEA - Finite element analysis

FGD - Flue gas desulfurization

HSM - Hardening soil model

JKR - Public works department

LEM - Linear elastic model

MCCM - Modified cam clay model

MCM - Mohr coulomb model

OMC - Optimum moisture content

PFA - Pulverised fuel ash

SEM - Scanning electron microscopy

SG - Specific gravity

SSM - Soft soil model

UCS - Unconfined compressive strength

UK - United Kingdom

ULS - Ultimate limit state

USA - United States of America

USCS - Unified soil classification system

UTHM - Universiti Teknologi Tun Hussein Onn

UTM - Universiti Teknologi Malaysia

TGA - Thermal gravimetric analysis

xxvii

XRD - X-Ray diffraction

XRF - X-Ray fluorescence

xxviii

LIST OF SYMBOLS

B - Width of foundation

c - Cohesion of soil

Cc - Compression index

cincrement - Cohesion increment

cpeak - Peak cohesion

cd peak - Peak cohesion for consolidated drained

c‟peak - Peak cohesion for consolidated undrained

cresidual - Residual cohesion

cd residual - Residual cohesion for consolidated drained

c‟residual - Residual cohesion for consolidated undrained

Cs - Swelling index

cu - Undrained shear strength

CU - Coefficient of uniformity

cv - Coefficient of consolidation

D - Depth factor

Df - Depth of foundation

DH - Depth to firm stratum

D10 - Effective size

D30 - Diameter finer than 30 %

D60 - Diameter finer than 60 %

E - Young's stiffness

Eincrement - Stiffness increment

Em - Young's stiffness of aluminum alloy

Eoed - Oedometer stiffness

Ep - Young's stiffness of concrete

Eur - Unloading stiffness

E50 - Secant stiffness

F - Factor of safety

xxix

g - Gravity, 9.81 m/s2

G0 - Elastic shear modulus

Gref - Shear modulus

Gs - Specific gravity

H - Height of embankment

h - Thickness of soil layer

Hs - Depth of failure

Ip - Plasticity index

kx - Horizontal permeability

ky - Vertical permeability

Ls - Linear shrinkage

mv - Coefficient of volume change

N - Scale factor

Ns - Stability coefficient

t - Test time

w - Natural water content

wL - Liquid limit

wopt - Optimum moisture content

wp - Plastic limit

- Slope angle

εa - Axial strain

- Internal friction angle

peak - Peak friction angle

d peak - Peak friction angle for consolidated drained

‟peak - Peak friction angle for consolidated undrained

residual - Residual friction angle

d residual - Residual friction angle for consolidated drained

‟residual - Residual friction angle for consolidated undrained

- Unit weight of soil

d - Dry unit weight of soil

dmin - Minimum dry unit weight of soil

dmax - Maximum dry unit weight of soil

sat - Saturated unit weight of soil

xxx

unsat - Unsaturated unit weight of soil

ν - Poisson ratio

n - Normal stress

1 - Major principle stress

3 - Minor principle stress

- Shear stress

ψ - Angle of dilatancy

xxxi

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Instrumentation calibration 248

B Hydrometer analysis 251

C Dry sieving test data 257

D Specific gravity data 260

E X- ray diffraction analysis 263

F Compaction test analysis 272

G Direct shear test analysis 277

H Permeability test 283

I Unconfined compression test 289

J California bearing ratio test 301

K One-dimensional consolidation test 304

L Thermal gravimetric analysis 329

M Laboratory physical model test results 338

N Standard error analysis 350

CHAPTER 1

INTRODUCTION

1.1 Background of Research

Coal is largely used around the world as a source or power generation. In

Peninsular Malaysia, the existing coal-fired power plants are Sultan Azlan Shah

Power Station, Manjung Perak (3 x 700 MW) commissioned in 2003, Sultan

Salahuddin Abdul Aziz Power Station Kapar (4 x 300 MW, 2 x 500 MW)

commissioned in 1988, Tanjung Bin, Pontian, Johor (3 x 748 MW) commissioned in

2005 and Jimah Port Dickson (2 x 752 MW) commissioned in 2008, as shown in

Figure 1.1. Sarawak has two coal fired-power plants which are Mukah (2 x 135 MW)

and Sejingkat (2 x 50 MW, 2 x 55 MW) (Coal-Fired Power Plants in Malaysia,

2010). Looking at the electricity generation mix, the percentage of coal remains

stable at an average of 8.6 percent from 1993-2010 and increased slightly to 12 and

14.1 percent in 2001 and 2002 respectively. However, in 2003, the percentage

increased tremendously from 14.1 percent to 24.6 percent of coal in the electricity

generation mix due to the commissioning of Sultan Azlan Shah Power Station

Manjung. According to Joseph (2005), with the two more new constructed coal-fired

power plants, Jimah, Port Dickson Negeri Sembilan and Tanjung Bin, Pontian Johor,

coal consumption has been expected to increase from 11 million tonne to 21 million

tonne in year 2012.

2

Figure 1.1: Location of coal fired power plants in

Peninsular Malaysia (Mahmud, 2008)

The burning of coal for power generation produced solid waste, referred to as

coal ash. The solids wastes are classified as fly ash (FA), bottom ash (BA), boiler

slag and fuel gas desulfurization (FGD). The large utilization of coal produces a

large volume of coal ash. In general, about 10% of the coal burned produces ash

(Huang, 1990, Karim, 1997, Muhardi, 2010 and Hassan, 2013). According to the

American Coal Ash Association (ACAA, 2003), the general production ratio of fly

and BA is approximately 80:20. The heavier ash that drops through the bottom of the

furnace, where it is collected in a funnel, is called BA. It is classified as wet or dry

BA depending on the type of furnace used and it is relatively coarse grained. The

lighter FA is carried through the boiler with the exhaust gases and is collected by ash

precipitators (Huang, 1990). FA accounts for 70 to 80 percent of the coal ash

produced by most electric power plants while BA constitutes about 10 to 18 percent

of the overall ash.

3

According to Mahmud (2003), the coal power plants in Malaysia are usually

designed using coal as blended materials in which bituminous coals are mixed with

sub-bituminous coal with the proportion of 70 %: 30 %. The main reason is to reduce

the cost of purchasing bituminous coal. The ash produced from this blended coal

might possess different properties as compared to the ash produced from the sole use

of bituminous coal or solely of sub-bituminous coal.

Basically the applications or potential applications of coal ash include the

cement and concrete industries, production of synthetic aggregates and zeolites,

backfill and embankment materials for highway construction, stabilization of

engineered soils for construction purposes, and improvement of soils behaviour for

agriculture and horticulture (Mahmud, 2008). The geotechnical, geochemical and

mineralogical properties of the coal combustion products may vary from individual

sample depending on the type of raw materials, feedstock handling and inflammation

condition.

Several projects in the United States of America (USA) and the United

Kingdom (UK) that use FA in embankment construction as structural materials have

shown economic savings, both to the highway department and power plant

companies (Yoon et al., 2009; Kim, 2003; Golden and DiGioia, 2003 and Sear,

2001). In Malaysia, however, there are still no well-known projects utilizing FA or

BA as materials in any Geotechnical Engineering or construction work. This may be

due to the fact that no abundant or excess of FA has been produced to date. As for

BA, perhaps it is because the properties have yet to be adequately looked into.

Pandian (2004) and Muhardi (2010) reported that, FA has good potential for

use in geotechnical engineering application. Its low specific gravity, freely draining

nature, ease of compaction, insensitiveness to change in moisture content, good

frictional properties, and others can be fully exploited in the construction of

embankment, roads, reclamations of low-lying areas and fill behind retaining

structures. It can also be used in reinforced concrete construction.

4

BA particles are much coarser than FA. The grain size typically ranges from

fine sand to gravel in size. According to Kumar and Vaddhu (2003), chemical

composition of BA is similar to FA but typically contains greater quantities of

carbon. BA tends to be relatively more inert because the particles are larger and more

fused than FA. Since these particles are highly fused, they tend to show less

cementitious/pozzolanic activity and less suited as a binder constituent in cement or

concrete products. However, BA can be used as a concrete aggregate or for several

other civil engineering applications where sand, gravel and crushed stone are used.

Chemical composition of both FA and BA shows some cementitious /pozzolanic

properties, which can result in time dependent change in the properties of products

made using this type of FA and BA.

A lot of studies had been concentrated on the properties of coal ash, but the

investigation on the coal ash mixtures is very limited. Kumar and Vaddu (2003)

observed that strength and stiffness of FA and BA mixtures vary with the curing

periods. Karim (1997) examined the effect of mixture proportions of FA and BA on

compaction and shear strength. He reported that the behavior of FA mixed with BA

(FA-BA mixtures) varies with the mixture proportions. For usage as fill materials, it

is anticipated that FA-BA mixtures will give economic advantage in which the cost

of purchasing the fill material will be reduced significantly. The utilization of FA-BA

mixture may answer the disposal and environmental problems in power plant

industry, beside an alternative lightweight material for embankment construction on

soft clay, as soil stabilization and in engineering construction. Due to lightweight

properties and strength gained with time, these materials hypothetically could be

used as replacement of soft soils, either in full replacement or partial replacement.

Physical models play a basic role in the development of geotechnical

engineering understanding. Physical modelling is carried out to validate theoretical

or empirical theories. Normally, physical modelling is performed to study the

particular aspects of the behaviour of prototypes. Full scale testing is an example of

physical modelling, where all features of the prototype are reproduced at full scale.

5

However, most physical models are constructed at smaller scales than the

prototype because it is expected to obtain information of response more rapidly and

allow more control over model details than full scale testing. One example of the

small scale physical modelling would be the laboratory physical model. As an

example, in the laboratory embankment model test, the material such as the soil to be

used can be chosen easily, while the boundary and loading conditions of the model

can be varied without difficulties. The costs of individual tests are correspondingly

lower than the full scale tests (Muhardi, 2010).

1.2 Problem Statement

Every year, the coal-fired power plant produced large volume of coal ash

which are FA and BA all over the world. Malaysia is also not excluded as a

contributor of large volume of FA and BA. Even though there is no report about the

producing of coal ash annually in Malaysia, but basically, about 10% of total weight

of the coal burned produces ash. Both the FA and BA is disposed as waste materials.

Landfill has been the primary method of disposal of these waste materials. The

problems that occur to disposing this coal ash are limited availability of land and

very costly since large volume of coal ash is generated. Besides that, the coal ash

presents a significant environmental problem to the surrounding area. However, this

environmental problem can be minimised by reducing the need for ash landfills.

From these problems, many researchers have proved that FA can be used in most

construction and Geotechnical Engineering works. So, many developed countries

have recycled the FA and minimise all of the above mentioned problems.

The used of BA is still very insignificant compared to the FA. Besides that,

the research about coal ash mixture properties is also very limited. Since FA particle

are very fine, mostly spherical and vary in diameter while BA particles are much

coarser than FA, the mixture of both materials will have a good potential in

6

construction industry, in particular the Geotechnical Engineering works. Hence, a

research is necessary to determine various properties of FA-BA mixtures such as a

physical, mechanical, chemical, microstructure and mineralogical, especially their

variation with time. This is because previous study showed that there was pozzolanic

reaction in FA-BA mixture. The usage of large volume of both FA and BA as FA-

BA mixture in geotechnical application may offer an attractive alternative, provided

that their properties and behaviour are fully known. However, although there are a lot

of studies related to the properties of coal ash internationally, the investigation about

the local coal ash is very limited. In particular for FA-BA mixture, the work is

insignificant, locally and internationally.

1.3 Objectives of Research

The aim of this research was to determine the suitable of FA-BA mixtures in

Geotechnical Engineering work, particularly as full and partial replacement of soft

soil based on laboratory experimental works and laboratory physical model tests. In

order to achieve the aim of this research, the following objectives have been fulfilled:

1. To determine the compaction characteristics of various FA-BA mixtures.

2. To determine various properties of compacted FA-BA mixtures such as

the physical, mechanical and chemical properties as well as the

microstructure and mineralogical characteristic and their changes with

time.

3. To determine the settlement performance of soft kaolin with and without

the replacement of FA-BA mixtures by means of single gravity

laboratory physical model tests.

4. To develop design charts for application of FA-BA mixtures as

alternative materials in geotechnical engineering works.

7

1.4 Scope of Research

In order to achieve the objectives of this research, the following scope had

been covered:

1. The coal ash used in this research had been collected from Tanjung Bin

Power Plant in Pontian, Johor. Samples of bottom ash were taken from

the ash pond while the fly ashes were taken from ash hoppers.

2. FA-BA mixtures had been prepared at six (6) different FA contents (0%,

30%, 50%, 70%, 90% and 100% by weight of the total samples) and

tested at three (3) curing periods (0, 14, and 28 days).

3. The laboratory physical model was constructed to examine the

settlement of single layer of soft clay and soft clay with fully and

partially replaced by FA-BA mixtures.

1.5 Significance of Research

1. Stabilisation mechanism of FA-BA mixtures had been established and

this contributed to the existing state of knowledge.

2. Properties and behavior of various FA-BA mixtures with time,

established from this study would be a reference to Geotechnical

Engineers in considering the usage of these materials in Geotechnical

Engineering works and construction. These could also be a baseline for

researchers working on FA-BA mixtures in the future.

8

3. The developed design charts on the usage of FA-BA mixtures in

Geotechnical Engineering work, particularly as soft soil replacement

could be used by other researchers as validation for numerical modeling

on the performance of FA-BA mixtures as soft soil replacement.

4. FA-BA mixtures would give economic advantage in which the cost of

purchasing the fill material would be reduced significantly. The

environmental impact of construction utilizing coal FA-BA mixtures

may be a concern to potential users of these materials. Results from this

research show that FA-BA mixtures will not give detrimental effects on

their surrounding environments. The utilizations of FA-BA mixtures

may answer the disposal and environmental problems in power plant

industry, beside an alternative lightweight material for replacement of

soft subgrade soils or as backfill in embankment construction on soft

soil.

1.6 Thesis Organisation

The thesis consists of eight (8) chapters. The essence of each chapter is as

follows:

Chapter 1 gives the introduction of the research that includes background,

statement of problem, objectives, scope and significance of research.

Chapter 2 reviews the generation of coal ash, its collection, disposal,

production and utilization in the world. An overview of the physical characteristics,

chemical and engineering properties of FA, BA and FA-BA are presented. Others are

also discussed that include the soft clay problems and physical modelling of

embankment.

9

Chapter 3 discusses the research methodology including the overview of the

research activities, testing programme, research planning and schedule, and

preparing of sample. The design, construction and testing of laboratory physical

model tests are also discussed.

Chapter 4 discusses the physical and mechanical characterization FA-BA

mixtures, including compaction, permeability, strength and compressibility

characteristics. This chapter also addresses the effect of curing age of 0, 14 and 28

days on the properties of FA-BA mixtures and the effects of FA composition in the

FA-BA mixtures.

Chapter 5 summarizes and discusses and the results of morphology,

mineralogy, chemical and corrosivity characteristics of FA-BA mixtures, including

SEM, XRD, XRF. This chapter also addresses the effect of FA compositions in the

ash mixtures and the curing periods on the properties of FA-BA mixtures.

Chapter 6 contains the performance of settlement analysis from the

experimental work by laboratory physical model tests. It includes the settlement of

soft clay layer and the soft clay layer which was fully and partially replaced by FA-

BA mixtures.

Chapter 7 explains the development of the design charts of coal ash mixtures

as alternative materials in geotechnical engineering works based on the results of the

experimental work and physical model. The conclusion and recommendations for

further research as drawn from this study are described in Chapter 8.

242

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