Post on 20-Jan-2020
PHYSICO-CHEMICAL AND MICROSTRUCTURE OF ARTIFICIAL SOILS
STABILISED WITH LIME-ZEOLITE
FELIX LING NGEE LEH
A thesis submitted in fulfilment of the
requirements for the award of the degree of
Doctor of Philosophy (Civil Engineering)
Faculty of Civil Engineering
Universiti Teknologi Malaysia
FEBRUARY 2016
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To my beloved father, mother, wife, daughters and siblings
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ACKNOWLEDGEMENT
This project will not be successful without the support from those who have
directly and indirectly helped me along the path. I am very grateful and would like to
convey my gratitude to every single one who has made this thesis possible.
Firstly, I would like to express my gratitude to Prof. Dr. Khairul Anuar bin
Kassim as my supervisor to this study. I would like to thank him for his inspire
guidance throughout the whole process of this project.
Secondly, specially thank to my co-supervisor Prof. Dr. Ahmad Tarmizi bin
Abdul Karim for his advices and guidance. Very appreciate to him for sharing his
experiences and knowledge in this project.
Thirdly, I would like to thank my superior Prof. Dato’ Dr. Ismail bin Bakar,
Head of Research Centre for Soft Soil (RECESS), UTHM for his support and help.
I would also like to thank all the technical staffs in the Geotechnical
Laboratory of FKA, UTM; Research Centre for Soft Soil (RECESS), UTHM; Ibnu
Sina, UTM, Materials Science Lab, FKM, UTM; Materials Science Lab, FKMP,
UTHM; Polymer Lab, FKKSA, UTM; Polymer Lab, FKMP, UTHM; Analytical Lab,
FKAAS, UTHM; Wastewater Lab, FKAAS, UTHM and others who had helped me a
lot during my experimental work.
Lastly, I would like to thank my parents, wife and two daughters who have
given me strong moral support throughout the study. Without them, I doubt that I
would have the chance to complete my research.
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ABSTRACT
The chemical stabilisation by admixing soil with lime is widely used in soft soil stabilization but its effectiveness in organic soil is low. Studies have shown that besides the organic content, the type of organic matter also influences the effectiveness of lime stabilisation. Artificial soils were utilized in this study to minimize potential influential factors that may be affected by the geochemistry variability of natural organic soils. Two types of organic matter, namely organic acid (contains humic acid and fulvic acid) and coco peat were utilized to simulate humified and non-humified organic matters that are normally found in natural organic soils. Commercially processed kaolin with different fineness and nSi/nAl were chosen as the base soil. The base soil and organic matter were manually mixed in different ratios based on their dry unit weight. Lime was partially replaced with zeolite with the aim to produce additive with self cementing matrix. The effectiveness of blended lime zeolite was investigated in this study. The total amounts of additives ranged from 7.5% to 15% were utilized based on the results of the Initial Consumption of Lime (ICL). Half of the remoulded test specimens were cured with a constant temperature of 50°C in an oven while the other part of the samples was cured at room temperature. The curing periods were set as 7, 28 and 56 days before being tested for unconfined compressive strength. Strength is utilized to determine the effectiveness of additives in stabilising artificial soils. The morphology of the stabilised and unstabilised materials was examined using a Field Emission Scanning Electron Microscope (FESEM), while the mineralogy of the materials was determined using X-Ray Diffraction (XRD) in order to unveil the hardening mechanisms of stabilised soils. General Linear Model (GLM) was utilized to determine the significant main factors, and interactions factors on the strength of artificial soil. The significant factors were used as the input parameters for multiple regression analysis to develop the strength prediction model. The models were utilised to predict the strength of stabilised materials within the inference space defined by the experiment. Overall, the mixture of coco peat and organic acid showed a deleterious effect on the strength of lime-zeolite stabilised artificial soils by lowering the soil’s pH and increasing its porosity. However, the results of the organic acid samples with different pH and cured in different curing temperature were inconsistent. The availability of needle-like structures or Calcium Silicate Hydrate (C-S-H) phase was used as an indicator of successful in the cementation process without being inhibited by organic matter. The 20% replacement of lime with zeolite was found to achieve the highest strength when used to stabilise artificial soils with 30% of organic acid under a laboratory environment. A 20% replacement of lime with zeolite was found to experience only a slight decrease in pH and was able to enrich the elemental properties of lime with silica and alumina, which are important for producing a cementing matrix in an alkaline environment.
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ABSTRAK
Penstabilan kimia dengan kapur telah digunakan secara meluas dalam penstabilan tanah lembut tetapi keberkesanannya adalah rendah untuk tanah organik. Keberkesanan penstabilan kapur dipengaruhi oleh kandungan organik dan jenis bahan organik. Tanah tiruan yang digunakan dalam kajian ini bertujuan mengurangkan faktor pengaruh yang berpunca daripada sifat kepelbagaian geokimia tanah organik semulajadi. Dua jenis bahan organik, iaitu asid organik (asid humic dan asid fulvic) dan gambut kelapa digunakan sebagai pengganti bahan organik terurai dan tidak terurai yang lazim ditemui dalam tanah organik semulajadi. Kaolin komersial yang mempunyai kehalusan dan nilai nSi/nAl yang berbeza telah dipilih sebagai tanah asas. Tanah asas dan bahan organik telah dicampur secara manual pada nisbah yang berlainan berdasarkan kepada unit berat kering. Sebahagian kapur adalah digantikan dengan zeolit untuk menghasilkan bahan campuran yang mempunyai matriks pensimenan sendiri. Kebolehkesanan campuran kapur zeolit telah dikaji dalam kajian ini. Jumlah bahan campuran yang digunakan adalah dalam lingkungan 7.5% kepada 15% bergantung kepada Kadar Penggunaan Kapur (ICL). Separuh daripada spesimen yang dibentuk semula akan dirawat dalam ketuhar pada suhu 50°C. Manakala sebahagian lagi dirawatkan pada suhu bilik. Tempoh rawatan sampel adalah ditetapkan pada 7, 28 dan 56 hari sebelum diuji untuk menentukan kekuatan tak terkurung. Kekuatan digunakan sebagai penentu keberkesanan bahan pencampur dalam menstabilkan tanah tiruan. Morfologi bahan distabil atau tidak distabil telah diuji menggunakan alat Pelepasan Imbasan Mikroskop Elektron (FESEM), manakala mineralogi bahan telah dikaji menggunakan kaedah Pembelauan Sinar-X (XRD) untuk mengenali mekanisma pengerasan tanah. Model Linear Umum (GLM) telah digunakan bagi menentukan kesesuaian faktor-faktor utama, dan interaksinya sebagai parameter masukan untuk analisis regresi berganda bagi membangunkan model ramalan kekuatan yang boleh digunakan untuk meramal kekuatan bahan stabil dalam ruang inferens yang ditakrifkan oleh ujikaji. Secara amnya, campuran gambut kelapa dan asid organik telah menunjukkan kesan negatif ke atas kekuatan tanah tiruan dengan menurunkan pH dan meningkatkan keliangan. Namun demikian, kesan asid organik ke atas kekuatan tanah tiruan adalah tidak konsisten untuk nilai pH campuran dan suhu rawat yang berbeza. Penemuan struktur berbentuk jarum atau fasa Kalsium Silika Hidrat (C-S-H) digunakan sebagai penanda kejayaan proses pensimenan tanpa diberhentikan oleh bahan organik. Penukaran 20% kapur dengan zeolit didapati mencapai kekuatan paling tinggi apabila digunakan untuk merawat tanah tiruan yang mengandungi 30% asid organik dalam suasana makmal. Sebanyak 20% penukaran kapur dengan zeolit hanya mengalami penurunan nilai pH yang rendah dan dapat memperkayakan ciri-ciri asas kapur dengan silika dan alumina. Elemen silika dan alumina adalah penting dalam menghasilkan matriks simen dalam suasana alkali.
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TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENTS iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES xii
LIST OF FIGURES xv
LIST OF ABBREVIATIONS & SYMBOLS xxvi
LIST OF APPENDICES xxviii
1 INTRODUCTION 1
1.1 Background of Study 1
1.2 Problem Statement 2
1.3 Objectives of Study 3
1.4 Significance of Study 4
1.5 Scope of Study 5
1.6 Organisation of Thesis 7
2 LITERATURE REVIEW 9
2.1 Introduction 9
2.2 Soil – Lime Reactions 10
2.2.1 Reactions Process of Lime with Soil 11
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2.2.1.1 Hydration 11
2.2.1.2 Flocculation 11
2.2.1.3 Cementation 12
2.2.1.4 Carbonation 12
2.2.2 Reaction Products of Pozzolanic Reaction 13
2.2.3 Factors that Affect Soil-Lime Reactions 17
2.2.3.1 Effect of Curing Periods 18
2.2.3.2 Effect of Curing Temperature 19
2.2.3.3 Types of Soil 22
2.2.3.4 Dosage of Lime 23
2.2.3.5 Types of Lime 28
2.3 Reactions of Soil Organic Matter in Chemical Stabilisation 29
2.3.1 Types of Soil Organic Matter 29
2.3.2 Effects of Soil Organic Matter on Chemical Stabilisation 33
2.3.3 Use of Coco Peat in Laboratory Study 41
2.4 Natural Zeolite 43
2.4.1 Characterisation of Natural Zeolite 44
2.4.2 Use of Natural Zeolite as Pozzolan in 47 Cement Industry
2.5 Chapter Summary 61
3 EXPERIMENTAL DESIGN AND
METHODOLOGY 62
3.1 Introduction 62
3.2 Characterisation of Natural Organic Soil 66
3.2.1 Field Explorations in Pontian, Johor 78
3.2.2 Field Explorations in Batu Pahat, Johor 83
3.3 Characterisation of Artificial Soil 84
3.4 Characterisation of Stabilisers 87
3.4.1 Lime-Hydrated Lime 89
3.4.2 Natural Zeolite 90
3.4.3 Lime-Zeolite 92
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3.5 Stabilisation of Artificial Soil 94
3.5.1 Design of Experiment 95
3.5.2 Mix Proportions of Artificial Soil and
Additive 103
3.5.3 Specimen Preparation 104
3.5.4 Specimen Curing and Testing 106
3.6 Chapter Summary 112
DATA ANALYSIS AND DISCUSSION OF SOILS
AND ADDITIVES 113
4
4.1 Introduction 113
4.2 Composition Properties of Natural Organic Soil 115
4.2.1 Mineralogical Composition 115
4.2.2 Chemical Composition 119
4.2.3 Composition of Soil Organic Matter 121
4.3 Artificial Soil 135
4.3.1 Physical Properties of Artificial Soil 135
4.3.2 Chemical Properties of Artificial Soil 148
4.3.3 Mineralogical of Artificial Soil 154
4.3.4 Microstructure of Artificial Soil 156
4.4 Properties of Additives 158
4.4.1 Hydrated Lime 158
4.4.2 Natural Zeolite 162
4.4.3 Blended Lime Zeolite 170
4.5 Chapter Summary 177
5 STRENGTH AND MICROSTRUCTURE
ANALYSIS OF ARTIFICIAL SOIL STABILISED
WITH LIME ZEOLITE 180
5.1 Introduction 180
5.2 Unstabilised Artificial Soil 181
5.2.1 Unconfined Compressive Strength 181
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5.2.1.1 Effect of Curing Temperature on Strength of Kaolin 188
5.2.1.2 Effect of Curing Temperature on Strength of Unstabilised Artificial Soil 192
5.2.1.3 Effect of pH on Strength of Unstabilised Artificial Soil 195
5.2.1.4 Effect of Organic Matter on Strength of Unstabilised Soil 197
5.2.2 Mineralogy, Microscopic and Elemental Analysis 200
5.3 Stabilised Artificial Soil 204
5.3.1 Unconfined Compressive Strength 204
5.3.1.1 Optimum Percentage of Lime for Artificial Soil 205
5.3.1.2 Effect of Organic Content on Strength of Lime Stabilised Artificial Soil 214
5.3.1.3 Effect of Lime replaced with Zeolite on Strength of Stabilised Kaolin 216
5.3.1.4 Effect of Lime replaced with Zeolite on Strength of Stabilised Artificial Soil 219
5.3.1.5 Effect of Curing Temperature on Strength of Stabilised Artificial Soil 222
5.3.1.6 Effect of pH on Strength of Stabilised Artificial Soil 226
5.3.1.7 Effect of Organic Matter on Strength of Stabilised Artificial Soil 230
5.3.1.8 Effect of Zeolite Increment on Strength of Lime Stabilised Artificial Soil 236
5.3.2 Mineralogy Analysis 238
5.3.2.1 Effect of Curing Condition 238
5.3.2.2 Effect of Curing Periods 240
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5.3.2.3 Effect of Organic Acid 251
5.3.2.4 Effect of Partial Replacement of Lime with Zeolite 252
5.3.3 Microscopic and Elemental Analysis 254
5.4 Chapter Summary 263
6 CONCLUSIONS & RECOMMENDATIONS 264
6.1 Introduction 264
6.2 Conclusions 265
6.2.1 Composition of Natural Organic Soil 265
6.2.2 Physico-Chemical Properties and Microstructure of Artificial Soil 266
6.2.3 Physico-Chemical Properties and Microstructure of Blended Lime Zeolite 268
6.2.4 Strength and Microstructure of Unstabilised Artificial Soil 269
6.2.5 Strength and Microstructure of Stabilised Artificial Soil 271
6.3 Recommendations 273
REFERENCES 275
Appendices A-C 289-347
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LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 Microstructural types observed for Calcium Silicate Hydrate 15
2.2 Summary of organic soil/peat soil stabilisation 24 2.3 Reactivity behavior of humic substances 31 2.4 Solubility behavior of humic substances 31 2.5 Summary of previous studies on the mechanism of soil
organic matter stabilisation 35
2.6 Guideline for selecting binders on the basis of soil classification shown in Figure 2.16 40
2.7 Chemical composition of natural zeolite and pozzolanic
materials (% w/w) 46 2.8 Compressive strength over curing periods of the zeolite
blended cement mortars 55 2.9 The clay-grout mixes 56 2.10 Mercury intrusion porosimeter (MIP) porosity over
curing periods of the zeolite blended cement pastes 57 2.11 Components and relative contents of the clinker-zeolite
blends 59 3.1 Reference standards for field explorations and
laboratory tests of natural organic soils 75 3.2 Detailing of field explorations in Pontian and Batu
Pahat, Johor 79
3.3 A variety of artificial soils 85
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3.4 Reference standards for laboratory tests of physical, chemical, microstructure and mineralogical properties of artificial soil
88 3.5 Blended lime zeolite 93 3.6 List of reference standards for test of stabilisers 94 3.7 Contributing factors and variable type selected for the
experiment
98 3.8 Subcategories of experiment 99 4.1 Bulk chemical composition of organic soil in Batu
Pahat, Johor 120 4.2 Quantitative correlation with humic acid & fulvic acid
and possible structural units 131 4.3 Particle size distribution of kaolin mixed with organic
acid 138 4.4 Specific surface and particle size distribution of kaolin-
organic acid 139 4.5 Bulk chemical composition of kaolin and organic acid 152 4.6 Bulk chemical composition of artificial soil 152 4.7 Approximate chemical composition of kaolin, organic
and artificial soils 153 4.8 Phase contents and crystallinity percentage of materials 155 4.9 Phase contents and crystallinity percentage of artificial
soils 156 4.10 pH value of hydrated lime from Lime Treat (M) Sdn.
Bhd. 159 4.11 Chemical composition of hydrated lime from Lime
Treat (M) Sdn. Bhd. 159 4.12 Total organic carbon of hydrated lime marketed by
Lime Treat (M) Sdn. Bhd. 161 4.13 Types of natural zeolite tested in this study 162 4.14 Bulk chemical composition of natural zeolites 164
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4.15 Total organic carbon of natural zeolites 165 4.16 Total alkaline and alkali earth elements and acid neutral
capacity of materials 165 4.17 Relative amorphous content and crystalline content 167 4.18 Possible structural units for natural zeolites 168 4.19 Particle size analysis of the blended lime zeolite 171 4.20 Specific gravity of blended lime zeolite 171 4.21 Bulk chemical composition of blended lime zeolite 173 4.22 Crystallinity of blended lime zeolite 174 4.23 Approximate chemical composition of additives 176 5.1 Unconfined compressive strength of unstabilised
artificial soil cured at 50°C 182 5.2 Unconfined compressive strength of unstabilised
artificial soil cured at room temperature 183 5.3 Details of artificial soils 198 5.4 Elemental composition of unstabilised artificial soil 204 5.5 Phase contents and crystallinity percentage of
10K0HA#, 7K3HA# and 5K5HA# using 10L0ZT 241 5.6 Phase contents and crystallinity percentage of 7K3HA*
and 5K5HA* using 10L0ZT 243 5.7 Phase contents and crystallinity percentage of 7K3HA*
and 5K5HA* using 8L2ZT 245 5.8 Phase contents and crystallinity percentage of 7K3HA*
and 5K5HA* using 5L5ZT 247 5.9 Phase contents and crystallinity percentage of 7K3HA*
and 5K5HA* using 0L10ZT 249 5.10 Approximate chemical composition of needle like/rod
like structure for soil type K7HA3* 261 5.11 Approximate chemical composition of needle like/rod
like structure for soil type K5HA5* 262
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LIST OF FIGURES
FIGURE NO. TITLE PAGE
2.1 SEM micrographs of different types of C-S-H phase formed in cement-Rice Husk Ash (RHA) paste after 120 days of hardening 14
2.2 SEM micrographs of cement paste at various curing
periods 14 2.3 Effect of drying technique on the formation of C-S-H
structure 16 2.4 Irreversible formation of C-S-H structure 16 2.5 Effect of partial pressures on C-S-H formation 17 2.6 Strength gains of Suddha’s soil over curing periods
with different lime content 19
2.7 Strength gains of soil over curing periods with
different lime-RHA contents 20 2.8 Strength gains of soil at different curing temperature
over increased curing periods 21 2.9 Changes in pH of lime stabilised soil over curing
periods at curing temperature of 20°C and 50°C 21 2.10 Strength gains in different types of soil stabilised with
a binder (25% lime and 75% cement) 23 2.11 Strength gains of soil in different humic acid contents
with different lime content 28 2.12 Electrons micrograph of moderately humified fibres
taken from an Irish Sphagnum peat 30 2.13 Electron micrograph of James Bay peat showing
networks of fibrous elements and perforated hollow particles 31
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2.14 Classification and characteristics of the organic matter in soil 32
2.15 Soil organic matter fractionation procedure 33 2.16 Soil classification zones based on the natural water
content and humic acid content
41 2.17 Coconut fibres 42 2.18 Representative image of cross-sectional view of
coconut 42 2.19 XRD pattern of the zeolite-Heulandite type II 47 2.20 XRD pattern of the zeolite-clinoptilolite 47 2.21 Fineness and water demand of Kimolos zeolitic tuffs
vs. volcanic glass 49 2.22 The plots of water demand-Blaine values over addition
of Clinoptilolite 49 2.23 Plots of strength gain in OPC and Clinoptilolite
blended cement mortars over hydration periods 502.24 Plot of strength vs. percentage addition of zeolite and
volcanic glass at different curing periods 51 2.25 Results of Fratini’s test for evaluating the ability of the
zeolite A and X to act as pozzolan. Solid line: Solubility curve of Ca(OH)2 52
2.26 Results of Fratini’s test at shorter and variable reaction
times. Square: OPC; triangle: blend A-25; circle: blend X-25. Reaction times in hours are indicated within the open symbols 53
2.27 Plots of compressive strength over hydration days for
zeolite blended cement mortars 54 2.28 Plot of reactive silica content over changes in strength
of cement mortars 55 2.29 UCS values for ten mixes at 28 days 56 2.30 Plot of compressive strength over porosity of zeolite
blended cement pastes 57 2.31 Effects of percentage zeolite on the properties of the
clay stabilised with cement-zeolite grout 58
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2.32 Plot of compressive strength of clinker-zeolite pastes over curing times 59
2.33 Unconfined compressive strength of the stabilised clay
mixed with cement-zeolite in the aggressive and control environments 60
3.1 Flow chart of experimental design and methodology 64 3.2 Sampling locations in Pontian, Johor 67 3.3 Peat boundary map of Pontian 68 3.4 Sampling locations in Batu Pahat, Johor 69 3.5 Geological map of Batu Pahat sampling locations 70 3.6 Sampling of peat and soft organic soils using
Eijkelkamp’s peat auger 71 3.7 Undisturbed tube sampler 71 3.8 Instrumental devices used for mineralogical and
molecular characteristics 73
3.9 GEONOR H60 Hand-held Vane tester 74 3.10 Unconfined compressive test on organic soil sample 75 3.11 Planetary micro mill – FRITSCH PULVERISETTE 7
premium line 77 3.12 Sampling location at MARDI Pontian, Pontian 79 3.13 Lithology map, Syit 133, Kukup 80 3.14 Location of cross-section 80 3.15 Detailing of cross-section A-A’ 81 3.16 Detailing of cross-section B-B’ 81 3.17 Peat/organic soil samples at Kg. Seri Kenangan,
Pontian 82
3.18 Peat/organic soil samples at Kg. China, Pontian 82 3.19 Organic soil samples at Parit Nipah, Batu Pahat, Johor 83 3.20 Organic soil sampling using 38mm cylindrical tube
sampler at Parit Nipah, Batu Pahat, Johor
83
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3.21 Components of artificial soil (kaolin, organic acid and coco peat)
85
3.22 Artificial soil mixed manually in pocket sealed plastic
bag
86 3.23 Malvern zeta sizer 87 3.24 Hydrated lime 90 3.25 Natural zeolite before and after grinded into fine
powder
91 3.26 Natural zeolite 93 3.27 Contributing factors considered for strength
enhancement of materials 96 3.28 Phase diagram of wet method of deep mixing 103 3.29 Remoulding mould for specimens 104 3.30 Preparation of soil specimen using compressive device 105 3.31 Constant volume of specimen 107 3.32 Artificial soil specimens cured at elevated temperature 108 3.33 Room temperature curing of specimens 109 3.34 Specimens cured at elevated temperature 110 3.35 Geocomp Load Trac II for UCS tests 111 4.1 X-ray diffractogram of peat soil at depth of 0.5 m –
1.0 m (MARDI Pontian) 116 4.2 X-ray diffractogram of soil at depth of 3.8 m –
10 m (MARDI Pontian) 116 4.3 X-ray diffractogram of soil at depth of 2 m –
4 m (P4, Pontian) 117 4.4 X-ray diffractogram of soil at depth of 1.66 m –
2.5 m (Parit Nipah) 118 4.5 X-ray diffractogram of soil at depth of 24 in. – 48 in.
(Parit Sidek) 118
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4.6 X-ray diffractogram of soil at depth of 0.74 m – 1.5 m (Batu Puteh) 119
4.7 FTIR spectra of peat soil at 0 m - 3.5m (PS1, MARDI
Pontian) 122 4.8 FTIR spectra of peat soil at 0 m - 3.8m (PS1, MARDI
Pontian) 122 4.9 FTIR spectra of peaty clay at 3.8 m – 4m (PS1,
MARDI Pontian) 123 4.10 FTIR spectra of peaty clay at 3.8 m – 10.0 m (PS1,
MARDI Pontian) 123 4.11 FTIR spectra of Permas Kelapa (P4) 124 4.12 FTIR spectra of P33 124 4.13 FTIR spectra of P264 125 4.14 FTIR spectra of Parit Nipah PA1 (0 m-1.5m) 125 4.15 FTIR spectra of Parit Nipah PA1 (1.0 m -2.0m) 126 4.16 FTIR spectra of Parit Nipah PA2 (1.0 m -2.0m) 126 4.17 FTIR spectra of Parit Nipah PA3 (1.66 m -2.5m) 127 4.18 FTIR spectra of Parit Sidek PA1 (24 in. – 48 in.) 127 4.19 FTIR spectra of Parit Sidek PA3 (24 in. – 48 in.) 128 4.20 FTIR spectra of Batu Puteh-P1 (0 m -1.5m) 128 4.21 FTIR spectra of Batu Puteh-P2 (0.74 m -1.5m) 129 4.22 FTIR spectra of PS1 MARDI Pontian’s peat soil at 3.5
- 3.8m vs. analytical grade humic acid of Sigma Aldrich 134
4.23 Particle size distribution of kaolin S300 mixed with
organic acid 136 4.24 Particle size distribution of kaolin FM-C mixed with
organic acid 137 4.25 Compaction curve of artificial soils 140
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4.26 Effect of organic acid on maximum dry density and optimum moisture content of kaolin S300 141
4.27 Effect of organic acid on maximum dry density and
optimum moisture content of kaolin FM-C 141 4.28 Plot of maximum dry unit weight versus organic
content 142 4.29 Plot of optimum moisture content (%) versus organic
content 143 4.30 Variation of maximum dry unit weight versus organic
content 143 4.31 Variation of optimum moisture content versus organic
content 144 4.32 Variation of specific gravity over organic acid content,
and organic content of kaolin S300 145 4.33 Variation of specific gravity over organic acid content,
and organic content of kaolin FM-C 146 4.34 Scatterplot of organic acid versus liquid limit, plastic
limit and optimum moisture content after compaction of kaolin S300 147
4.35 Scatterplot of organic acid versus liquid limit, plastic
limit and optimum moisture content after compaction of kaolin FM-C 148
4.36 Relationship of LOI (%), pH and sulfate content of
artificial soils with organic acid (%) 149 4.37 Zeta potential of kaolin S300 over pH change 150 4.38 Zeta potential of kaolin S300 (70%) and organic acid
(30%) over range of pH 150 4.39 Zeta potential of kaolin S300 (50%) and organic acid
(50%) over range of pH 151 4.40 Zeta potential of kaolin S300 (70%), organic acid
(30%) and coco peat (5%) over range of pH 151 4.41 XRD diffractogram of unstabilised kaolin S300 vs.
kaolin FM-C 154 4.42 SEM micrograph of kaolin S300 and organic acid 157
xxi
4.43 SEM micrograph of artificial soils 157 4.44 Particle size distribution of hydrated lime 158 4.45 SEM micrograph of hydrated lime- mag. 10kX 160 4.46 SEM micrograph of hydrated lime- mag. 25kX 161 4.47 FTIR spectra of natural zeolite 167 4.48 SEM micrograph of zeolite- Mechastone - mag. 10kX 169 4.49 SEM micrograph of zeolite- Mechastone - mag. 15kX 169 4.50 Particle size distribution of blended lime zeolite 171 4.51 pH of blended lime zeolite 172 4.52 XRD diffractogram of blended lime zeolite 174 4.53 SEM micrograph of 8L2ZT - mag. 10kX 175 4.54 SEM micrograph of 5L5ZT - mag. 10kX 175 4.55 Scanning electron micrograph of the fractured surface
of limestone 176 4.56 Overlap of FTIR spectra of lime zeolite 177 5.1 Effect of organic acid and kaolin on unconfined
compressive strength of unstabilised artificial soil cured at 50°C over curing periods 184
5.2 Effect of organic acid and kaolin on unconfined
compressive strength of unstabilised artificial soil cured at room temperature over curing periods 185
5.3 Effect of curing temperature and contents of organic acid on unconfined compressive strength of unstabilised artificial soil (Kaolin S300 + organic acid) over curing periods 186
5.4 Effect of curing temperature and contents of organic
acid on unconfined compressive strength of unstabilised artificial soil (Kaolin FM-C + organic acid) over curing periods 186
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5.5 Effect of curing temperature and mixture of organic acid and coco peat on unconfined compressive strength of unstabilised artificial soil (Kaolin S300) over curing periods 187
5.6 Effect of pH on unconfined compressive strength of
unstabilised artificial soil cured at 50°C over curing periods 187
5.7 Effect of coco peat on unconfined compressive
strength of unstabilised artificial soil cured at 50°C over curing periods 189
5.8 Main effect plots for strength of kaolin at different
curing temperatures 190 5.9 Interaction plot for strength of kaolin at different
curing temperatures 190 5.10 Individual value plot of moisture loss 191 5.11 Main effect plots for strength of artificial soils at
different curing temperatures 193 5.12 Interaction plot for strength of artificial soils at
different curing temperatures 194 5.13 Main effect plots for strength of artificial soil with
different contents of NaOH and cured for different periods 196
5.14 Interaction plot for strength of artificial soils with
different contents of NaOH and cured for different periods 196
5.15 pH of 7K3HA with different molarities of NaOH 197 5.16 Main effect plots for strength of kaolin mixed with
organic matter 199 5.17 Interaction plot for strength of kaolin partially
replaced with organic matter 199 5.18 Effect of organic acid and coco peat on itensity peaks
of unstabilised artificial soils cured at 50°C 201 5.19 SEM micrograph of unstabilised artificial soils with
organic acid and coco peat cured at 50°C 201
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5.20 SEM micrograph of unstabilised artificial soils (with only organic acid) 202
5.21 Identical cracks on particles of unstabilised artificial
soils (with only organic acid) 203 5.22 Scatterplot of strength versus initial density and final
density of stabilised artificial soils 206 5.23 Scatterplot of strength versus final moisture content of
cured artificial soils 207 5.24 Boxplot of strength versus main effects 207 5.25 Solubility of soil minerals at various pH 208 5.26 Boxplot of differences in density versus main effects 209 5.27 Main effects plot for strength of lime stabilised
artificial soils 210 5.28 Interaction plot for strength of lime stabilised artificial
soils 210 5.29 Initial consumption of lime for artificial soils 211 5.30 Dissolution curves of the studied humic acid particles 211 5.31 Individual value plot of pH 212 5.32 Main effect plots for strength of soil with different
organic acid contents 214 5.33 Interaction plot for strength of artificial soils stabilised
with lime 215 5.34 Initial consumption of lime for soil Kaolin S300 -
organic acid 216 5.35 Main effect plots for strength of kaolin cured with lime
zeolite 217 5.36 Interaction plot for strength of kaolin stabilised with
lime zeolite 218 5.37 Main effect plots for strength of artificial soils
stabilised with lime zeolite 220 5.38 Interaction plot for strength of artificial soils stabilised
with lime zeolite 220
xxiv
5.39 pH of lime stabilised artificial soils at various percentage of organic acid 221
5.40 Main effect plots for strength of artificial soils
stabilised using lime zeolite and cured at different curing temperature 223
5.41 Interaction plot for strength of artificial soils stabilised
using lime zeolite and cured at different curing temperature 223
5.42 Main effect plots for strength of artificial soils
stabilised with lime zeolite and cured at different curing temperature 225
5.43 Interaction plot for strength of artificial soils stabilised
with lime zeolite and cured at different curing temperature 225
5.44 Main effect plots for strength of artificial soils with
different contents of NaOH and cured with lime zeolite for different periods 227
5.45 Interaction plot for strength of artificial soils with
different contents of NaOH and cured with lime zeolite for different periods 228
5.46 pH of soil 7K3HA added with NaOH and lime-zeolite
at 0 day 229 5.47 Main effect plots for strength of stabilised kaolin
partially replaced with organic matter 231 5.48 Interaction plot for strength of stabilised kaolin
partially replaced with organic matter 231 5.49 Main effect plots for strength of stabilised Kaolin FM-
C partially replaced with organic acid 234 5.50 Interaction plot for strength of stabilised Kaolin FM-C
partially replaced with organic acid 235 5.51 Main effect plots for strength of lime stabilised
artificial soils with increased percentage of zeolite 237 5.52 Interaction plot for strength of lime stabilised artificial
soils with increased percentage of zeolite 237 5.53 X-ray diffractogram of stabilised 7K3HA* using
10L0ZT cured for 56 days 239
xxv
5.54 X-ray diffractogram of stabilised 5K5HA* using 10L0ZT cured for 56 days 240
5.55 X-ray diffractogram of stabilised 7K3HA using
10L0ZT cured at 50°C- reaction products (C-S-H) 251 5.56 X-ray diffractogram of stabilised 5K5HA using
10L0ZT cured at 50°C- reaction products (C-S-H) 252 5.57 X-ray diffractogram of reaction products for artificial
soil 7K3HA cured at room temperature 253 5.58 SEM micrograph of needle like structure for sample
7K3HA*-10L0Z 255 5.59 SEM micrograph of needle like structure for sample
5K5HA*-10L0ZT 255 5.60 SEM micrograph of needle like structure for sample
7K3HA*-8L2ZT 255 5.61 SEM micrograph of needle like structure for sample
5K5HA*-8L2ZT 256 5.62 SEM micrograph of needle like structure for sample
7K3HA*-5L5ZT 256 5.63 SEM micrograph of sample 5K5HA*-5L5ZT cured for
56 days 256 5.64 SEM micrograph of sample 5K5HA*-5L5ZT cured for
7 days 257 5.65 SEM micrograph of sample 7K3HA*-0L10Z cured for
56 days 258 5.66 SEM micrograph of sample 7K3HA*-0L10Z cured for
7 days 258 5.67 SEM micrograph of sample 5K5HA*-0L10Z cured for
56 days 259 5.68 SEM micrograph of sample 5K5HA*-0L10Z cured for
7 days 259
xxvi
LIST OF ABBREVIATIONS AND SYMBOLS
Al - Aluminum
Al2O3 - Aliminium Oxide
ATR - Attenuated Total Reflectance
BS - British Standard
Ca2+ - Calcium Cation
CAH - Calcium Aluminum Hydrate
CaO - Calcium oxide
CaCO3 - Calcium Carbonate
Ca(OH)2 - Calcium hydroxide
CaSO4 - Calcium Sulphate
CSH - Calcium Silicate Hydrate
EDX - Energy Dispersive X-ray Analyzer
Fe2O3 - Ferric Oxide
FESEM - Field Emission Scanning Electron Microscope
FTIR - Fourier Transform Infrared
GPS - Global Position System
H2O - Water
HCI - Hydrochloric Acid
IC - Inorganic Carbon
ICDD - International Center for Diffraction Data
ICL - Initial Consumption of Lime
JMG - Minerals and Geoscience Department Malaysia
K+ - Potassium Cation
LL - Liquid Limit
LOI - Loss of Ignition
MARDI - Malaysia Agricultural Research & Development Institute
MC - Moisture Content
xxvii
Mg2+ - Ion Magnesium
MgO - Magnesium oxide
MP - Modified Peat
Na+ - Sodium Cation
NaOH - Sodium Hydroxide
(OH)- - Hydroxide ion
OPC - Ordinary Portland Cement
PI - Plasticity Index
PL - Plasticity Limit
ppm - Parts per million
RECESS - Research Centre for Soft Soil
RHA - Rice Hush Ash
SiO2 - Silica
SG - Specific Gravity
SOM - Soil Organic Matter
TC - Total Carbon
TEM - Transient Electromagnetic
TG - Thermal Gravimetric
TGA - Thermal Gravimetric Analyzer
TOC - Total Organic Carbon
UCT - Unconfined Compression Test
UTHM - Universiti Tun Hussein Onn Malaysia
UTM - Universiti Teknologi Malaysia
VP - Virgin Peat
WDXRF - Wavelength Dispersive X-ray Fluorescence
XRD - X-ray Diffraction
XRF - X-ray Fluorescence
ZrO2 - Zirconium Oxide
θ - Failure angle
xxviii
LIST OF APPENDICES
APPENDIX TITLE PAGE
A Summary of laboratory test results of MARDI
Pontian, Pontian; Parit Nipah, Parit Sidek & Batu Puteh, Batu Pahat; Particle size analysis of natural organic soil – CILAS test results; XRD diffractogram of peat/organic soil; FTIR spectra of peat/organic soil samples; Spreadsheet for mix design of specimens; Example of main effects plot and interaction plot
289 B Specification sheet of Kaolin S300 and FM-C;
Specification sheet of Organic Acid; XRD Diffractogram of organic acid (Humic acid and Fulvic acid); Physico-chemical properties of Kaolin and Artificial soil; Specific gravity test results of additives; XRD Diffractogram of Hydrated Lime; FTIR Spectra of Hydrated Lime; FESEM-EDX of Hydrated Lime; XRD Diffractogram of Zeolite; FTIR Spectra of Zeolite; FESEM-EDX of Zeolite 319
C Bulk chemical composition of stabilised artificial soils;
Strength prediction models 340
CHAPTER 1
INTRODUCTION
1.1 Background of Study
Malaysia, as a tropical country is reported to experience humid and wet
climates throughout the year. The organic materials in this region are found to be
well preserved over a long period of time because of their physico-chemical and bio-
chemical processes (Bujang and Faisal, 2007). Plants that were preserved and
disintegrated under anaerobic and high water content conditions have resulted in an
accumulation of organic soils in this region. Organic soil that is found to be low in
strength and high in compressibility is categorized as soft soils.
Soft soil stabilisation by admixing it with chemical stabilisers namely lime
and cement are able to improve its engineering properties. The improved engineering
properties of stabilised soil are found to be better in strength and variability control,
lower in compressibility and deformability, and increase in volume stability and
durability (Hausmann, 1990). However, Koslanant et al. (2006) found that lime or
cement stabilisation of soil are less effective when dealing with high organic content.
Soils with high organic content normally experience lower strength increase after
stabilisation, if compared with inorganic soils stabilised with the same types and
amounts of additive (Ruis and Hansson, 2001).
Organic soils which are formed by disintegration of organic matter exhibit
various engineering characteristics with the amount of organic contents and stages of
decomposition. Hence, the organic soil is categorized based on its contents (British
2
Standards Institution, 2015; Department of Standards Malaysia, 2005; IKRAM,
1995)and stages of decomposition (Von post classification system) in order to better
describe the soil behaviour. However, the engineering properties of organic soil with
organic matter higher than 20% are not suitable to be estimated using the mechanical
criteria of conventional mineral soil. (Bujang and Faisal, 2007). Indeed, the
properties of organic soil are not only governed by the organic contents but also vary
with types of organic matter (Huttunen and Kujala, 1996; Koslanant et al., 2006;
Kujala, et al., 1996; Kuno, et al., 1989).
1.2 Problem Statement
Lime has been found to be an effective stabiliser for soil as it is able to
increase its strength and stability under the action of water (National Lime
Association, 2004). However, lime is not very effective in stabilising organic soils
(Ruis and Hasson, 2001) even though the successfulness of organic soil stabilisation
is sometimes deduced from empirical test data. The major problem in the use of
calcium based stabiliser (including lime and cement) in the stabilisation of organic
soils is the effectiveness of stabiliser over time (Bujang, 2006; Chen et al., 2009;
Koslanant et al., 2006). Thompson (1966) explained that the pozzolanic reactions
were obstructed in organic soil because the soil particles (as the primary source of
silica and/or alumina) used in the stabilisation process, were “coated” by organic
cations, inhibiting the silica and/or alumina from dissolution, which results in an
absence of silica and/or alumina in pozzolanic reaction. As a result, the desired
improvement is hard to gain when dealing with high organic content. Sometimes, the
improvement might also disappear over time.
Chen et al. (2009) found that calcium-based stabilisers like lime and cement
are not suitable for soils with high organic content as the detailed mechanism
involved in organic soil stabilisation is still not fully understood. It was explained
that the organic molecules absorb calcium ions that are necessary for chemical
reactions between stabilisers and soils thus inhibiting the growth of reaction
products, such as Calcium Silicate Hydrate (C-S-H) and Calcium Aluminates
3
Hydrate (C-A-H). The reaction products of the chemical reaction (pozzolanic
reaction) are the main contributor for strength enhancement. Thus, a detail study of
its physico-chemical behavior is needed to understand the mechanisms involved in
stabilisation.
In addition, Chen et al. (2009) also urged that alternative methods other than
adding extra stabiliser must be used even with organic content as low as 1%. The
effectiveness of lime or cement stabilisation can be also affected by the types of
organic matter. Hence, it is practically difficult to determine the threshold of organic
content that will retard the lime or cement stabilisation.
1.3 Objectives of Study
This research study aims to investigate and evaluate the use of Zeolite as
pozzolan for lime stabilisation of artificial soils. Hence, the research study was
undertaken with the following objectives:-
(i) To analyse the molecular structure in terms of functional group and its
x-ray diffraction pattern in an attempt to identify the composition of
natural organic soil as reference guide to design artificial soil;
(ii) To establish the use of artificial soils with organic acid and coco peat,
and lime-zeolite as additives by determining its physico-chemical and
microstructural properties;
(iii) To assess the changes induced on the mineralogy and microstructure
of stabilised artificial soils with its unconfined compressive strength;
(iv) To evaluate the effect of various contributing factors, namely curing
periods, curing temperature, types and contents of inorganic soil,
types and contents of organic matter and percentage of additives
(lime-zeolite) on strength enhancement of artificial soils;
4
(v) To establish strength prediction models for stabilising artificial soils
with Lime- Zeolite
1.4 Significance of Study
The deleterious effect of organic matter on the strength of soil stabilised with
lime and cement is not yet fully understood yet even though many studies have been
completed. One of the main challenges is identifying the types and quantity of
organic matter of the soil because the types and content of organic matter are found
to change with the humification process and vary with time. Hence, there is a need
for a comprehensive study of using artificial soil with specific organic matter and
organic contents, especially the soil organic matter widely available in the peat/
organic soil of Malaysia.
In addition, even though natural zeolite (a kind of natural pozzolan that is
widely available in our neighboring region) has a successful application in the
cement industry as a pozzolan, there are no known studies on the use of it in soil
stabilisation with lime, or in particular with organic soil. In fact, the concept of
partially replacing lime with zeolite (rich in alumino-silicate) in order to produce a
self-cementing matrix in aqueous environment with organic matter is also novel.
Hence, there is a need to identify the possibilities of using zeolite to stabilise soil
with organic matter.
Therefore, there is a need to identify the composition of local natural organic
soils in order to design artificial soils that are able to address local problems. By
identifying the physico-chemical and microstructure of artificial soils stabilised with
lime-zeolite, this study will able to address the above mentioned gaps in knowledge
and may be useful for geotechnical engineers and/ or those who wish to develop
projects on local organic soil deposits.
5
1.5 Scope of Study
This study was carried out in four stages with the aim to investigate and
evaluate the use of zeolite as pozzolan for lime stabilising soil with organic matters.
The first stage focused on the composition properties of the natural organic soil in
Pontian, and Batu Pahat, Johor which served as an input for designing artificial soil.
Field exploration studies for peat and organic soils were carried out in Pontian, and
Batu Pahat, Johor. The tropical peat and organic soil samples were collected using a
peat auger or a tube sampler and tested for its mineralogy and organic composition.
All the specimens were dried at the low temperature of 50°C in order to avoid the
potential losses of volatile organic components in higher temperatures. The mineral
composition of natural organic soils was determined using X-Ray Diffraction (XRD)
and the elemental chemical composition was determined using X-Ray Fluorescence
(XRF). The functional group of soils was identified by using Fourier Transform
Infrared Spectroscopy (FTIR) which helped determine the organic composition of
the soils.
The second stage was focused on examining the material properties and
behaviour of artificial soils, natural zeolites and hydrated lime. The composition of
artificial soils was chosen by the composition details of natural organic soils.
However, the ratio of each component (organic matter vs. inorganic matter) was
purposely changed with the aim to study the effect of its content. Two different kinds
of processed soil (Kaolin S300 and Kaolin FM-C) with different ratios of silicate
over aluminates and size distributions were chosen as the base soil for this study. The
kaolin S300 and Kaolin FM-C are commercially processed inorganic soils from
Kaolin (M) Sdn. Bhd. Two different types of organic matter: organic acid and coco
peat were utilized in this study as substitute material of humified matter and non-
humified matter in the natural organic soils. The organic acid, which consists of
humic acid and fulvic acid, was originally imported by a local fertilizer shop from
China as soil conditioner for agriculture, while the coco peat (also known as coir
dust) was obtained by pre-drying and sieving the coir fiber/ coconut fiber through a
sieve aperture of 2 mm. The use of organic acid and coco peat as substitute material
of organic matter was also reported by other researches in horticulture studies (Abad,
et al., 2002; De Silva, and van Gestel, 2009; Sharma, et al., 2014) and chemical
6
stabilisation studies (Kujala, et al., 1996; Tremblay, et al., 2002; Modmoltin, et al.,
2004; Shao, et al., 2007; Xu, et al., 2007; Zhu, et al., 2009; M. Yunos, et al., 2013).
In addition, the hydrated lime was also directly obtained from Lime Treat (M) Sdn.
Bhd. in Pasir Gudang in order to insure freshness. The natural zeolite utilized in this
study was imported from Indonesia and marketed as MECHASTONE by Anugerah
Alam Sdn. Bhd.
The third stage included the parametric study which focused on the influence
of organic matter (organic acid and coco peat), the percentage of additive (lime-
zeolite), curing periods, and curing temperature on the mechanical properties of
stabilised and unstabilised soil. A variety of artificial soils with known types and
percentage of organic matter and inorganic matter was prepared and mixed with
various percentages of lime and zeolite as additive for stabilisation. A series of
parametric studies were planned and carried out in order to determine the effect of
inorganic material (two types of kaolin soil), and organic matter (humified matter-
organic acid; non-humified matter- coco peat) on the properties of soils. Besides that,
various ratios of lime zeolite were utilized to stabilise the artificial soils with the aim
to determine the suitability of zeolite as pozzolan in the lime stabilisation of soils.
The amount of additives utilized in this study was in the range of 7.5% to 15% by
referring to its initial consumption of lime (ICL). The remoulded specimens were
subjected to an unconfined compressive test after curing for 7, 28 or 56 days. The
specimens were either cured in a humid box (room temperature curing) or in an oven
with a constant temperature of 50°c. It was found that the elevated temperature of
50°c is ideal for enhancing the strength of specimen stabilised with lime (George, et
al., 1992). A total of 636 specimens were tested for its unconfined compressive
strength by counting in 3 replicates for each mixture. A selective small portion of
specimen obtained from tested specimen after a UCT test was further oven dried and
grinded into small particles for microstructure tests. The changes in mineralogy and
morphology were determined by using X-Ray Diffraction (XRD), and a Field
Emission Scanning Electron Microscope (FESEM), respectively with the aim to
identify its hardening mechanism. The findings of this study are served as a reference
on the use of zeolite as pozzolan for lime stabilisation of organic matter that
artificially added in.
7
Lastly, a group of strength prediction models were established by using a
statistical approach in which the correlation between the various contribution factors
namely organic content, curing periods, curing temperature and additive content
were taken into consideration. The other factors namely, moulding water content,
types of compaction and compactive effort are keep constant through controlled
experiments. The General Linear Model (GLM) was utilized to determine the
significance of the main factors, two-factor interactions, and three factor interactions.
The significance factors and interactions were utilized in multiple regression
analyses to develop a strength prediction model which can be utilized to predict the
strength of stabilised materials within the inference space defined by the experiment.
1.6 Organisation of Thesis
This thesis aims to investigate the physico-chemical and microstructure of
artificial soils stabilised with lime and zeolite. Overall, this thesis consists of six
chapters with each chapter focusing on a different subject matter as follows.
Chapter 1 is the introduction for the whole thesis which gives an overview of
the background of study, the problem statement, objectives of study, significance of
study and scope of study. It covers a brief overview on the current problems and
issues when stabilising soil with organic matter. In addition, this chapter also
explains the approach taken in order to understand the mechanisms of organic matter
stabilised with blended lime zeolite or in particular the role of zeolite as pozzolan.
Chapter 2 presents the review of literature related to this study, which
includes the materials chosen in this study namely organic soils, lime and zeolite.
This chapter also encompasses topic likes soil-lime reactions, the influence of
organic matter on pozzolanic reactions, the use of humic acid and coco peat as a
substitute in producing artificial soil, and the use of zeolite as pozzolan.
Chapter 3 focuses on the material characterisation and selection which
includes the exploration study of organic soil in Pontian, and Batu Pahat, Johor as
8
well as the methods and analysis of the physico-chemical, microstructure and
mineralogy of artificial soils. Furthermore, this chapter also includes details of the
characterization and selection of additive (hydrated lime and natural zeolite) that was
used in this study.
Chapter 4 presents the compositional properties of natural organic soils in
Pontian and Batu Pahat, Johor. The findings served as an input for designing
artificial soils. In addition, the physico-chemical and mineralogical properties of a
variety of artificial soils, and additives are also presented and discussed in this topic.
The material properties reported in this topic unveiled the characteristics and
behaviour of artificial soils and additives.
Chapter 5 presents the unconfined compressive strength of artificial soils with
and without stabilisation by additives. The effect of various contributing factors on
the strength of artificial soils such as the curing periods, curing temperatures, organic
contents, organic types and percentage of additives (hydrated lime and zeolite) are
analyzed using a statistical approach to determine the correlation. The findings from
the study are also compared with other researchers’ work. Besides that, the analysis
and discussion on the morphology of the materials under the Scanning Electron
Microscope, the bulk chemical composition and its phases determined via X-ray
techniques, the functional group of materials via Infrared Spectroscopy are also
presented in this chapter.
The last chapter in this thesis- Chapter 6 gives a summary of the whole result
as an integral part of the study. The recommendations for future works or further
works are also provided in this topic.
CHAPTER 2
LITERATURE REVIEW 2.1 Introduction
Stabilisation work of soil by lime and cement is a common improvement
method used for stabilizing soft clay and dredged sludge. Soft clay found near the
surface and the dredged sludge usually contains high organic content, which reduces
the effectiveness of lime or cement stabilisation.
In this study, lime was chosen as the main binder because lime was reported
by Onitsuka et al. (2003) to be more sensitive with organic matter compared to
cement. According to Koslanant et al. (2006), cement stabilisation was found to
cause water and soil pollution by leaching of hexavalent chromium.
Literatures on the reactions of soil with lime are reviewed and reported in the
first part of this chapter which covers an overview of short-term and long term
reactions of soil with lime. The second part of this chapter focuses on the effects of
organic materials in the chemical stabilisation of soil. The reactions of the organic
matter with lime and cement are reviewed in order to understand the problems
encountered by previous researchers when dealing with organic soils. Whereas, the
third part of this chapter reviews the case studies of using artificial soil in laboratory
studies with the aim to reduce the variability in soil properties. The last part of this
chapter is dedicated to the use of natural zeolites as pozzolan. Lime-pozzolan
mixtures are normally necessary if the soils are not sufficiently reactive. Additional
10
silica and alumina from the pozzolan potentially forms a stronger cementitious
matrix that forms a lime-stabilised layer.
Overall, this review aims to:
a) Outline the reactions of soil with chemical stabilizers – lime and also
types of reaction product;
b) Identify various factors that may influence the reactions of lime with soil;
c) Categorize types of organic matter in soil and explain how soil organic matter
can influence the reactions of lime with soil;
d) Outline the use of humic acid and coco peat as artificial soil in laboratory
studies with the aim to explain the interaction mechanism in between each
component;
e) Outline the characteristics of natural zeolite and explain its use as pozzolan in
cement industry and soil stabilization;
2.2 Soil – Lime Reactions Lime, a kind of calcium based stabilizer, has a long history in soil
stabilisation. It was first used in 1924 as a soil stabiliser to strengthen a short stretch
of highway in the United States of America (Bell, 1996). Since then, lime is used in
modern construction, primarily for stabilising clayey soils. It is found that lime is not
very effective for cohesionless soils unless other additives are used.
Generally, there are two types of lime which are commonly used in
stabilisation: hydrated lime [Ca(OH)2], and quicklime [CaO]. Lime modifies the soil
11
through cation exchange and stabilises it after the modification process has
completed.
2.2.1 Reaction Process of Lime with Soil
In the short term, soil will experience hydration (for quicklime) and
flocculation (ion exchange) when lime is added. Whereas, the longer reactions of
lime with soil will be a cementation and carbonation process that contributes to the
gain of strength.
2.2.1.1 Hydration
Quicklime is found to be able to react almost immediately with water in soil.
The reaction results in a drying process that is effective in improving the strength of
soil. Besides that, the heat generation and expansion of the lime when used in lime
columns and layers can further enhance the consolidation effect.
CaO + H2O → Ca(OH)2 + Heat (280 Cal/gm of CaO) (2.1)
2.2.1.2 Flocculation
The cations that absorbed to the surface of clay sized soil, such as Sodium
(Na2+) are ready to exchange with Calcium (Ca2+) when lime is mixed with soil. The
cation exchange process will change the structural components of the soil, causing
the soil to flocculate, aggregate or coagulate. From the perspective of its chemical
reaction, the flocculation, aggregation or coagulation of the soil particles are actually
caused by the replacement of univalent alkali ions that are normally attracted to the
negatively charged clay particles with the dissociated bivalent calcium ions in the
12
pore water. The reaction will reduce the plasticity of clay which is measured as
Atterberg limits. As a result of the reaction, the workability, strength and stiffness of
soil are increased.
2.2.1.3 Cementation
The cementation process is the second stage of the clay-lime reaction. The
process will only occur when the alumina-silicate of the soil mineral is disassociated
from its original lattice by the hydroxyl ions released from the lime forming new
compounds such as calcium silicate hydrate (C-S-H) and calcium aluminate hydrates
(C-A-H) gels. This process is also known as a pozzolanic reaction.
Ca2+ + 2(OH)- + SiO2 → C-S-H (2.2)
Ca2+ + 2(OH)- + Al2SiO3 → C-A-H (2.3)
The pozzolanic reaction is responsible for the strength enhancement of
stabilised soil. Lime is found to be an effective stabilizer in fine-grained soils in
which the effectiveness of stabilizer will be increased with the surface area of the soil.
Cementation, is, however, limited by the amount of available silica. Increasing the
quantity of lime will increase strength only up to the point where all the silica of the
clay is used up; adding too much lime can actually be counterproductive. This is in
contrast to stabilisation with cement, where strength continues to improve with the
amount of admixture.
13
2.2.1.4 Carbonation
Reaction of lime with carbon dioxide in the open air or in voids of the ground
forms a relatively weak cementing agent. This may be beneficial where lime is
plentiful; the CaCO3 formed will not react any further with the soil.
2.2.2 Reaction Products of Pozzolanic Reaction
The gain of strength in soil stabilised by calcium based stabilisers such as
lime and cement is mainly contributed by the cementation/ solidification process that
occurs through pozzolanic reaction. Reaction products of pozzolanic reaction,
namely Calcium Silicate Hydrate (C-S-H) or Calcium Aluminum Hydrate (C-A-H)
are able to reduce the porosity and increase the bonding of the materials through its
unique structure. There are different types of C-S-H structure observed under the
Scanning Electron Microscope namely needle like, reticular and flocs-like as shown
in Figure 2.1. Different forms of C-S-H are found when mortar cement is mixed with
Rice Husk Ash when compared to the C-S-H formed in plain mortar cement (Cizer
et al., 2006).
Apart from the materials involved in the pozzolanic reactions, the structure of
C-S-H is also found to be different throughout the curing periods as shown in Figure
2.2. The Calcium Silicate Hydrate (C-S-H) formed in cement paste at early stage is
shown in Figures 2.2(a) - (b). The C-S-H structures were progressively developed as
fabric structure as curing time increased. Besides that, some needle-like ettringite
(formed in the early stage) and rod-like ettringite were found in Figures 2.2(d) - (f) as
curing time increased. Ettringite (3CaO.Al2O3.3(CaSO4). 32H2O) is the hydration
products of calcium aluminate in cement with sulfate ions from dissolution of
gypsum and water (Prasanphan et al., 2010).
In fact, there are several types of C-S-H structure as observed using the
electron microscope and it can be described as needles, thin foils, hollow tubes and
14
amorphous gel (Jennings et al., 1981). A classification system is proposed and
summarized in Table 2.1 with the aim to explain the relationship between types of C-
S-H and its forming period.
(a) SEM micrographs of needle-like and reticular C-S-H phases formed inside the pore of the mortar cement after 120 days of hardening
(b) SEM micrographs of flocs-like C-S-H phases formed in the matrix of mortar cement mixed with RHA at ratio of 5-5 after 120 days of hardening
Figure 2.1 SEM micrographs of different types of C-S-H phase formed in cement-
Rice Husk Ash (RHA) paste after 120 days of hardening (Cizer et al., 2006)
(a) 1 day (b) 3 days (c) 7 days
(d) 14 days (e) 28 days (f) 28 days
Figure 2.2 SEM micrographs of cement paste at various curing periods
(Nontananandh et al., 2005)
15
Table 2.1 : Microstructural types observed for Calcium Silicate Hydrate*
(Jennings et al., 1981)
Classification Period formed Morphology and habits
Type E First few hours; Stage
I and II
Type O Between 4 and 24h;
stages III and IV
Type 1 Forms from type O
during first few days
Type 1' Can be formed from
type O during first
few days
Type 3 Froms from type O
after several days
Type 4 After first 24h
Early
- Thin flakes or foils which, when dried,
become cigar-shaped tubes 0.25 µm
long, radiating from C3S grains at all
angles.
Middle
- Amorphous gel ≈ 0.5 µm thick
surrounding C3S grains; behaved as
wet plastic material for first several
days; changed into other morphologies
depending on space available
- Slightly tapered needles 0.75-1.0 µm
long, radiating perpendicularly to C3S
grains, with aspect ratio of ≈ 10;
formed from type O in open areas
>1 µm; encouraged by drying and/ or
age
- Tapered fibers 0.25-0.5 µm long, often
branching; formed from type O by
pulling apart particles; seen only on
young fracture surfaces
Late
- Partly crumpled foils which are
interlocked; formed as type O ages
and/ or dries in regions where original
interparticle spacing is < 1 µm
- Dense gelatinous inner product *w/n = 0.5.
16
Fonseca and Jennings (2010) found that the morphology of the C-S-H
structure is more dependent on drying process rather than length of curing periods.
The findings suggested that the drying process contributed to the formation of fiber-
like or needle like structures as shown in Figure 2.3. A rapid drying process favors
the formation of thinner and longer needles when compared to a slow drying process.
Besides that, other factors such as pre-drying process and partial pressures will also
affect the formation of reaction products as shown in Figure 2.4 and Figure 2.5,
respectively.
(a) Rapid drying (b) Dry in 2 hours
Figure 2.3 Effect of drying technique on the formation of C-S-H structure
(Fonseca and Jennings, 2010)
(a) No pre-drying (b) Pre drying at 76% RH desiccator
Figure 2.4 Irreversible formation of C-S-H structure (Fonseca and Jennings, 2010)
17
(a) 100% RH (b) 88% RH
(c) 75% RH (d) 33% RH
Figure 2.5 Effect of partial pressures on C-S-H formation (Fonseca and Jennings,
2010)
2.2.3 Factors that Affect Soil-Lime Reactions Various factors that affect soil-lime reactions are the environment of the
reaction, the nature of soil, types and dosage of lime, and the mixing efficiency of the
soil-lime. The environment includes the temperature and time of curing. The nature
of soil refers to types of soil or other factors such as specific surface area, amount of
reactive silica, moisture content or organic content of soil, which directly contribute
to the efficiency of reactions. Practically, typical correlation factors of 0.25 to 0.5 are
always applied to the laboratory results (Keller Ground Engineering, 2014). One of
18
the reasons is because of the lower mixing efficiency in-situ when compared to the
remoulding works conducted in the laboratory. The mixing efficiency is not
reviewed in detail in this subtopic because this study is solely a laboratory study.
2.2.3.1 Effect of Curing Periods
Strength gains in soil stabilised with lime is found to be time dependent
because the main contributor for strength enhancement is the pozzolanic reaction.
This reaction will occur when the alumina-silicate of the soil mineral is disassociated
from its original lattice by the hydroxyl ions released from the lime forming new
compounds such as calcium silicate hydrate and calcium aluminate hydrates gels.
Hence, it is recommended in BS 1924: Part 2 (1990) that curing periods of 7, 28, 56
and 112 days are more appropriate for lime stabilised soil in order to make sure that
the strength is increased satisfactorily. A curing period of 28 days is recommended
for lime stabilised soil if a single fixed curing period was chosen.
Studies by Umesha et al. (2009), and Jha and Gill (2006) have shown that the
strength of lime and lime-RHA stabilised soil increased with curing periods. It is
found that the strength increment of soil was more significant at higher lime content
and also at the initial periods (as shown in Figure 2.6 and Figure 2.7). Hence, it is
shown that lime is required for pozzolanic reaction and the cementation process is
started even at the initial 7 days.
19
Figure 2.6 Strength gains of Suddha’s soil over curing periods with different lime
content (Umesha et al., 2009)
2.2.3.2 Effect of Curing Temperature
One of the factors that increased the strength gains in lime stabilised soil is
through increased curing temperature. Many studies, such as by Dzulkarnain (2007),
Jha and Gill (2006), Rao and Shivananda (2005), and George et al. (1992) have
found that increased temperature not only increased the strength gain and also the
rate of strength gain. Hence, it is shown in Figure 2.8 that the strength of lime
stabilised soil is higher at higher curing temperature. Besides that, the strength
increment rate will also increase at a higher temperature range when comparing a
temperature range of 30°C to 40°C with a temperature range of 20°C to 30°C.
It is believed that the gain of strength is resulted from the accelerated
pozzolanic reaction at higher temperature resulting from the increased kinetics of
soil-lime reactions. As a result, more lime is consumed during the pozzolanic
reaction and thus a significant drop of pH is expected at a higher temperature as
shown in Figure 2.9 (Al-Mukhtar et al., 2010).
20
Figure 2.7 Strength gains of soil over curing periods with different lime-RHA*
contents (Umesha et al., 2009) *RHA – Rice Husk Ash
21
Figure 2.8 Strength gains of soil at different curing temperature over increased
curing periods (Dzulkarnain, 2007)
Figure 2.9 Changes in pH of lime stabilised soil over curing periods at curing
temperature of 20°c and 50°c (Al-Mukhtar et al., 2010)
Curing (day)
Stre
ngth
(kPa
)
* Suhu = Temp.
22
2.2.3.3 Types of Soil
Soil is generally considered the material formed by the breakdown of rock
through physical and/or chemical weathering. Soil can be categorized into gravel,
sand, silt and clay depending on its particle size distribution. A smaller particle size
will exhibit higher surface area, speeding up the chemical stabilisation process using
lime.
However, some types of soil namely peat soil may not be formed by the
weathering of rock (Powrie, 1997). It is produced through the decomposition of
organic matters by the microbial that exist in the area. Hence, the content of organic
matter varies with the stages of decomposition and thus contains different types of
compounds including proteins, sugars, and polysaccharides (Dingus, 1999).
One of the main factors that govern the strength gain is the nature of the soil
(Keller Ground Eng., 2014). It is shown in Figure 2.10 that the strength gains in
different types of soil are varied even though the same type (lime/cement mixture at
a ratio of 25/75) and fixed contents of stabiliser (100kg/m3 and 150kg/m3) were used.
The plot shows that clayey Silt and clay gained the highest strength when compared
to other types of soil. In fact, the stabilisation effect very much depends on reactivity
of soil which may change with the content of clay minerals, its pozzolanicity, organic
and sulfur content (Ǻhnberg et al., 1995). However, the strength increment in lime
stabilized clayey soil will usually increase to a certain limit which depends on its
reactive silica and clay content (Umesha et al., 2009). The limit is always known as
optimum lime content.
Comparatively, the mud and peat soil have the lowest strength gain as shown
in Figure 2.10. Various works have been carried out by numerous researchers in this
region with the aim to increase the strength of organic soil/ peat soil as summarized
in Table 2.2. However, types of organic matter in the soil are not well described in
most of the reviewed studies. Thus, the influential effect of each organic matter on
the strength of organic soil is not well understood. Hence, deleterious effects of
23
organic matter on the strength gain of lime stabilised soil are further reviewed in
Subtopic 2.3 which focused on the reactions of organic matter in soil stabilisation.
Figure 2.10 Strength gains in different types of soil stabilised with a binder (25%
lime and 75% cement) (Ǻhnberg et al., 1995)
2.2.3.4 Dosage of Lime
In general, the dosage of lime required depends on the nature of soil. The
strength linearly increases with dosage until a certain limit, which is known as the
optimum lime content (Figure 2.11). The optimum lime content varies with the soil
and depending on its clay content and the reactive silica (Umesha et al., 2009). The
extra lime content over the optimum lime content will most likely remain unreacted
and act as a filler material which results in a negative effect on strength gains. Bell
(1996) explained that the negative effect could be due to the fact that lime itself has
neither appreciable friction nor cohesion and thus extra lime will not able to
contribute for strength enhancement.
24
Table 2.2 : Summary of organic soil/peat soil stabilisation
Researcher(s) Characteristics of
Soil
Additive(s) utilized Findings & Comments
Arman and
Munfakh (1972)
Lime Stabilization
of Organic Soils
- Organic content =
0%, 10% and 20%
-Calcium hydroxide
-Percentage of lime
utilized = 12%
- UCS of stabilized soil decreased with the increment of
organic content.
- UCS of stabilized inorganic soil (0% organic content) in the
range of 200 – 210 psi for a curing period of 7 days to 28
days.
- UCS of stabilized organic soil (10% organic content) in the
range of 110 – 160 psi for a curing period of 7 days to 28
days.
- UCS of stabilized organic soil (20% organic content) in the
range of 60 – 80 psi for a curing periods of 7 days to 28 days
- Some calcium ions from added lime are used to satisfy the
base-exchange capacity of the organic matter, and fewer
ions are available for the pozzolanic reaction. Hence, the
strength increment was low for soil with 20% organic
content comparative to soil with 10% organic content.
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