physicochemical properties of batu pahat clay using … · 2017. 3. 2. · daripada plat akrilik...

PHYSICOCHEMICAL PROPERTIES OF BATU PAHAT CLAY USING

ELECTROKINETIC STABILISATION METHOD

NURUL SYAKEERA BINTI NORDIN

A thesis submitted in

Fulfillment of the requirement of the award of the

Master Degree of Civil Engineering

Faculty of Civil & Environmental Engineering

Universiti Tun Hussein Onn Malaysia

86400 Parit Raja, Johor

December 2015

i

ABSTRACT

`

Electrokinetic Stabilisation (EKS) method is a combination process of

electroosmosis and chemical grouting. This study involves the investigation on the

EKS method performances in stabilising soft clay soils. Stabilising agents will assist

the EKS method by inducing it to the soil under direct current and its movements

which is governed by the principle of electrokinetic (EK). The objective of this

research is to study the effectiveness of EKS method in increasing the strength of soft

clays. EKS test rig was made by transparent acrylics plate (15mm) with 420 mm depth,

170mm width and 358 mm length. Soil compartment in the container was 278 mm

length while for anode and cathode reservoirs were 40 mm length. Two reactors were

set up by using 1.0 M of calcium chloride (CaCl2), sodium silicate (Na2SiO3) as the

electrolyte and stainless steel plates as the electrode. The method was conducted at

Research Centre for Soft Soil (RECESS), UTHM. EKS method was being performed

for a period of 21 days, with a constant voltage gradient (50 V/m). This method was

carried out in two phases where the difference between them is a combination of the

stabilising agent. The two combinations of stabilising agents in phase 1 and phase 2

were CaCl2 – distilled water (DW) and CaCl2 – Na2SiO3, respectively. Results of the

physical and chemical parameters towards untreated and treated soil were presented.

Generally, showing the strength of treated soil for both phases was increasing near the

cathode section with 27.83 kPa and 27.67 kPa. LL and PI for treated soil showed the

highest value which occurred near the cathode, while PL seems consistant with the

values from untreated soil. The calcium (Ca+) and sodium (Na+) concentrations in soil

were increasing compared to the untreated soil, hence it has proven that the application

of stabilisers in EK treatment is more effective in increasing the strength and the

stability of soils.

ii

ABSTRAK

Kaedah penstabilan elektrokinetik (EKS) merupakan gabungan proses antara

elektroosmosis dan penurapan bahan kimia. Kajian ini telah dijalankan dengan

mengkaji prestasi EKS dalam menstabilkan tanah liat lembut. Penambahan agen

penstabil dalam tanah akan menambah baik lagi prestasi EKS dibawah aliran arus

terus dimana pergerakannya dikawal oleh prinsip elektrokinetik (EK). Objektif kajian

ini adalah untuk mengkaji keberkesanan kaedah EKS dalam meningkatkan kekuatan

tanah liat lembut. Pelantar ujikaji EKS telah dihasilkan untuk kajian ini yang diperbuat

daripada plat akrilik lut sinar (15 mm) dengan kedalaman 420 mm, kelebaran 170 mm

dan kepanjangan 358 mm. Ruangan untuk tanah dalam pelantar tersebut adalah

sepanjang 278 mm manakala ruangan untuk takungan anod dan katod adalah

sepanjang 40 mm. Dua reaktor telah ditetapkan iaitu elektrolit dan elektrod; untuk

elektrolit dengan menggunakan 1.0 M kalsium klorida (CaCl2) dan sodium silika

(Na2SiO3) manakala untuk elektrod dengan menggunakan plat keluli tahan karat.

Ujikaji telah dijalankan di Pusat Penyelidikaan Tanah Lembut (RECESS), UTHM.

Ujikaji EKS telah dijalankan selama 21 hari dengan nilai voltan yang malar (50 V/m).

Kajian ini telah dijalankan pada dua fasa di mana perbezaan antaranya adalah pada

kombinasi agen penstabil yang digunakan. Kombinasi agen penstabil untuk fasa

pertama adalah CaCl2 – air suling (DW) manakala bagi fasa kedua adalah CaCl2 –

Na2SiO3. Keputusan data ujikaji dalam menentukan parameter fizikal dan kimia

terhadap tanah yang telah dirawat dan tidak dirawat oleh EKS telah dibentangkan.

Umumnya, data ujikaji menunjukan kekuatan tanah yang telah dirawat meningkat

sekitar kawasan katod dengan nilai sebanyak 27.83 kPa untuk fasa pertama dan 27.67

kPa untuk fasa kedua. Nilai LL dan PI bagi tanah yang telah dirawat menunjukan nilai

tertingginya terhasil di kawasan katod, manakala nilai PL pula menunjukkan nilai

yang konsisten dengan tanah yang tidak dirawat. Kepekatan kation untuk kalsium (Ca+)

dan sodium (Na+) juga meningkat dibandingkan dengan tanah yang tidak dirawat,

iii

justeru itu ianya membuktikan aplikasi agen penstabil di dalam rawatan EK adalah

lebih efektif dalam meningkatkan kekuatan dan kestabilan tanah.

iv

For my beloved parents, Mak and Abah, my siblings and my lovely friends.

v

ACKNOWLEDGEMENT

First and foremost, thanks to Allah Almighty Who enabled me to complete my

research with successfully. For my parents, thanks for your moral support, whose

financial support and passionate encouragement made it possible for me to complete

my research.

I submit my heartiest gratitude to my respected supervisor Dr Saiful Azhar bin

Ahmad Tajudin for his sincere guidance and invaluable help for completing this

research. And also to my co-supervisor Ass. Prof. Dr Aeslina binti Abdul Kadir for

sharing her knowledge and her priceless help during my study.

In addition, thank you to Office for Research, Innovation, Commercialization

Consultancy Management (ORICC) for granting me with Postgraduate Incentive

Research Grant (GIPS) and Ministry of Higher Education for sponsored my studies fees.

Finally, I would like to acknowledge with gratitude, for the help and support

from my family, friends, research teammate and all parties who have been involved in

preparing this thesis.

vi

CONTENT

ABSTRACT i

ABSTRAK ii

DEDICATION iv

ACKNOWLEDGEMENT v

CONTENTS vi

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF SYMBOLS AND ABBREVIATIONS xvii

CHAPTER 1 INTRODUCTION 1

1.1 Introduction 1

1.2 Problem statement 3

1.3 Research aim and objectives 4

1.4 Scope of study 5

1.5 Significance of this study 6

CHAPTER 2 LITERATURE REVIEW 7

2.1 Introduction 7

2.2 Marine clay 7

vii

2.3 Clay mineralogy 11

2.4 Engineering properties of clay minerals 14

2.5 Physical chemistry of clays 15

2.6 Clay-water-electrolyte system 16

2.7 Ion distribution in clay-water systems 17

2.8 Diffuse double-layer theory 18

2.9 Soil surface charge 20

2.10 Cation exchange 21

2.10.1 Ion selectivity 22

2.10.2 Pozzolanic reaction 24

2.11 Electrokinetic phenomena 25

2.11.1 Electroosmosis 26

2.11.2 Streaming potential 28

2.11.3 Electrophoresis 29

2.11.4 Migration or sedimentation potential 31

2.12 Effect of electrical gradient 32

2.12.1 Electrolysis 32

2.12.2 Electrode reaction 33

2.13 Electrokinetic stabilisation 34

2.13.1 History and development of electrokinetic 36

2.13.2 Factors affecting electrokinetic

stabilisation 37

2.13.3 Advantages and disadvantages of

viii

electrokinetic stabilisation 39

2.13.4 Solution for disadvantages of electrokinetic

stabilisation 40

CHAPTER 3 METHODOLOGY 42

3.1 Introduction 42

3.2 Material properties 44

3.2.1 Soil 44

3.2.2 Chemical stabilisers 44

3.2.3 Electrode 46

3.2.4 Power supply 47

3.2.5 Design of EKS test rig 47

3.2.6 Sample preparation 49

3.3 Test for physical properties of soil 51

3.3.1 Atterberg limit 51

3.3.1.1 Liquid limit 52

3.3.1.2 Plastic limit 53

3.3.2 Specific gravity (Gs) 53

3.3.3 Moisture content 54

3.3.4 Undrained shear strength 55

3.4 Test for chemical properties of untreated soil 56

3.4.1 Mineralogy in soil 56

3.4.2 Cations concentration 57

3.4.3 pH 59

ix

3.5 EKS laboratory experiment set-up 61

3.6 Phase 1 of EKS 63

3.7 Phase 2 of EKS 63

3.8 Monitoring of EKS testing 63

3.9 Laboratory testing of treated soil 64

3.9.1 Test for physical properties of treated soil 65

3.9.2 Test for chemical properties of treated soil 67

CHAPTER 4 RESULTS AND DISCUSSIONS 68

4.1 Introduction 68

4.2 Monitoring data 68

4.2.1 Electric current 69

4.2.2 Inflow and outflow 71

4.2.3 pH of electrolytes 74

4.3 Soil classification for untreated soil 76

4.4 Atterberg limit 77

4.5 Undrained shear strength 84

4.6 Moisture content 88

4.7 Relationship between undrained shear strength and

moisture content 90

4.8 pH of clay soils 91

4.9 Mineralogy composition in soil 94

4.10 Cations concentration 99

x

CHAPTER 5 CONCLUSIONS 106

5.1 Introduction 106

5.2 Monitoring data 107

5.3 Physical parameters of treated soil 107

5.4 Chemical parameters of treated soil 109

5.5 Conclusion 110

5.6 Limitation of the study 110

REFERENCES 112

APPENDIX 119

xi

LIST OF TABLES

2.1 The stratigraphic units for quaternary deposits 9

2.2 Physical properties of marine clay from previous study 10

2.3 Chemical and mineralogical properties of marine clay from

previous study 11

2.4 Classification of electrokinetic phenomena 26

2.5 Various reported research and case studies relating to

electrokinetic stabilisation 35

2.6 Factors affecting electrokinetic stabilisation 38

4.1 Soil properties for Batu Pahat clay 76

4.2 Percentage of minerals in clay with distance from anode 95

xii

LIST OF FIGURES

2.1 Distribution of Cenozoic sediments in Peninsular Malaysia 8

2.2 Location of marine clay deposits in Southern Region of

Peninsular Malaysia 9

2.3 (a) Silica tetrahedron 12

(b) Silica sheet 12

(c) Alumina octahedron 12

(d) Octahedral (gibbsite) sheet 12

2.4 (a) Diagram of the structures of kaolinite 13

(b) Diagram of the structures of illite 13

(c) Diagram of the structures of montmorillonite 13

2.5 Distribution of ions adjacent to a clay surface according to the

concept of the diffuse double layer 17

2.6 The Helmholtz electric double layer 19

2.7 Stern’s model and ions distribution in the electric double layer 20

2.8 Flocculation of clay platelets parallel arrangement of clay

particles with hydrated water layer 23

2.9 Flocculation of clay platelets edge-to-face attraction induced by

thin water layer, which allows attractive forces to dominate 24

2.10 Electroosmosis 27

xiii

2.11 Streaming potential 29

2.12 Electrophoresis 30

2.13 Migration or sedimentation potential 31

3.1 Flowchart of methodology 43

3.2 Calcium chloride 45

3.3 Stainless steel plate 46

3.4 Schematic diagram of EKS test rig 48

3.5 EKS test rig drawing scale 49

3.6 Atterberg limit stage 52

3.7 Sample in pyknometer bottle 54

3.8 Hand vane shear 55

3.9 Acetic acid + soil sample before and after filtrate 58

3.10 Samples in labelled plastic bottle after filtrate 58

3.11 Sample in pallet shape 59

3.12 pH meter 60

3.13 Standard buffer solution 60

3.14 Consolidation stage through sample 61

3.15 EKS experiment set-up from front view 62

3.16 EKS experiment set-up from side view 62

3.17 Plan view of location for laboratory testing after EKS experiment 64

3.18 Front view of depth for laboratory testing after EKS experiment 65

3.19 Soil sample after EKS experiment 65

3.20 Moisture content of treated soil sample 66

xiv

4.1 Electric current for CaCl2 – DW system with time 70

4.2 Electric current for CaCl2 – Na2SiO3 system with time 70

4.3 Inflow and outflow of CaCl2 for CaCl2 – DW system with time 71

4.4 Inflow and outflow of DW for CaCl2 – DW system with time 72

4.5 Inflow and outflow of CaCl2 for CaCl2 – Na2SiO3 system

with time 73

4.6 Inflow and outflow of Na2SiO3 for CaCl2 – Na2SiO3 system

with time 73

4.7 pH of electrolytes for CaCl2 – DW system with time 74

4.8 pH of electrolytes for CaCl2 – Na2SiO3 system with time 75

4.9 Liquid limit for CaCl2 – DW system with distance from anode 77

4.10 Plastic limit for CaCl2 – DW system with distance from anode 78

4.11 Plastic index for CaCl2 – DW system with distance from anode 78

4.12 Liquid limit for CaCl2 – Na2SiO3 system with distance from anode 79

4.13 Plastic limit for CaCl2 – Na2SiO3 system with distance from anode 80

4.14 Plastic index for CaCl2 – Na2SiO3 system with distance

from anode 80

4.15 Liquid limit for CaCl2 – DW and CaCl2 – Na2SiO3 systems

with distance from anode 82

4.16 Plastic limit for CaCl2 – DW and CaCl2 – Na2SiO3 systems


4.17 Plastic index for CaCl2 – DW and CaCl2 – Na2SiO3 systems


4.18 Undrained shear strength for CaCl2 – DW system with distance

from anode 85

xv

4.19 Undrained shear strength for CaCl2 – Na2SiO3 system with

distance from anode 85

4.20 Undrained shear strength for CaCl2 – DW and CaCl2 – Na2SiO3

systems with distance from anode 87

4.21 Moisture content for CaCl2 – DW system with distance

from anode 88

4.22 Moisture content for CaCl2 – Na2SiO3 system with distance

from anode 89

4.23 Moisture content for CaCl2 – DW and CaCl2 – Na2SiO3 systems


4.24 Relationship between undrained shear strength and moisture

content for CaCl2 – DW and CaCl2 – Na2SiO3 systems 91

4.25 pH for CaCl2 – DW system with distance from anode 92

4.26 pH for CaCl2 – Na2SiO3 system with distance from anode 92

4.27 pH for CaCl2 – DW and CaCl2 – Na2SiO3 systems with distance

from anode 94

4.28 Image of soil fabric for untreated clay 97

4.29 Image of soil fabric treated using CaCl2 – DW system

near the anode 97


at the middle 97


near the cathode 98

4.32 Image of soil fabric treated using CaCl2 – Na2SiO3 system

near the anode 98


at the middle 98

xvi


near the cathode 99

4.35 Na+ concentration for CaCl2 – DW and CaCl2 – Na2SiO3 systems


4.36 Al+ concentration for CaCl2 – DW and CaCl2 – Na2SiO3 systems


4.37 Ca+ concentration for CaCl2 – DW and CaCl2 – Na2SiO3 systems


4.38 Fe+ concentration for CaCl2 – DW and CaCl2 – Na2SiO3 systems


4.39 K+ concentration for CaCl2 – DW and CaCl2 – Na2SiO3 systems


4.40 Mg+ concentration for CaCl2 – DW and CaCl2 – Na2SiO3 systems


xvii

LIST OF SYMBOLS AND ABBREVIATIONS

UTHM - Universiti Tun Hussein Onn Malaysia

RECESS - Research Centre for Soft Soils

FKAAS - Faculty of Civil & Environmental Engineering

EK - Electrokinetic

EKS - Electrokinetic Stabilisation

DC - Direct Current

BS - British Standard

ASTM - American Society for Testing and Materials

PL - Plastic Limit

LL - Liquid Limit

PI - Plastic Index

SL - Shrinkage Limit

Gs - Specific Gravity

A - Area

𝜌𝑠 - Particle Density

w - Moisture Content

wi - Initial Moisture Content

Hi - Initial Height

𝛾𝑤 - Unit Weight of Water

Vs - Volume of Sample

Ms - Mass of Sample

Mw - Mass of Water

T - Torque

Cu - Undrained Shear Strength

Cc - Compression Index

V - Voltage

xviii

CaCl2 - Calcium Chloride

DW - Distilled Water

Na2SiO3 - Sodium Silicate

CSH - Calcium Silicate Hydrate

CAH - Calcium Aluminate Hydrate

ke - Coefficient of Electroosmotic Hydraulic Conductivity

H+ - Hydrogen

OH- - Hydroxide

SEM - Scanning Electron Microscope

XRF - X-ray Flourescence

XRD - X-ray Diffraction

AAS - Atomic Absorption Spectrocospy

TCLP - Toxicity Characteristic Leaching Procedure

1

CHAPTER I

INTRODUCTION

1.1 Introduction

The high population in Malaysia indirectly influenced the rapid growth of

industrialisation which requires an extensive construction of infrastructure. The new

projects, maintenance and upgrading of facilities provided significant input to the

overall development. The circumstances have compelled engineers to construct earth

structures over soft clay deposit which have a low bearing capacities coupled with

excessive settlement characteristic. The engineers have to assure the earth structures

on the areas which consists mainly of soft clays, peat and other organic deposits are

able to withstand the imposed load from the upper structures without causing any

failure. It is also poses major construction and maintenance problems due to low

bearing capacities and high deformation behavior (Indraratna, Balasubramaniam &

Balachandran, 1992; Taha, Ahmed & Asmirza, 2000).

Soil properties such as low shear strength, excessive compression, collapsing behavior,

high swell potential are some of the undesirable properties of soils in geotechnical

engineering and those properties would cause severe distress to the structures. These

undesirable properties must be altered to render the soils as problem free soils so that

the trouble free structures could be constructed on such soils (Gingine et al., 2013).

Braja (2006), emphasises that settlement is a deformation occurring because of

foundation loading. These main criteria are important to ensure safe and stability of

2

the foundation design. The main problem faced in construction is the low permeability,

low strength and low bearing capacity on clayey soil of soft soil. It is because,

sometimes the soil or fill material cannot reach the required specification in

geotechnical aspect and need to be improved.

One of the method to solve the problem is the conventional method by doing ground

improvement of the soil. Conventional methods are widely used to solve this problem

by preloading the soft layer with surcharge and installing vertical drains to accelerate

consolidation. Mitchell & Soga (2005) emphasises that, there are two options to

improve the ground by physical or chemical treatment/stabilisation. Chemical

stabilisation is an effective ground improvement technique for controlling erosion

(Vinod et al., 2010). Sometimes conventional methods are not suitable to stabilise the

soil therefore new methods are needed to stabilise soft soils with low hydraulic

conductivities while minimizing ground movements.

The poor behavior of soil such low shear strength and large compressibility have force

the engineers to find a solution to improve the ground condition very efficiently. One

of the solution is electrokinetic stabilisation treatment which uses the principle of

electroosmosis, electromigration and electrocementation which appropriate for fine

grained soil (Gingine et al., 2013). Electrokinetic is an applicable technique to

transport of charged particles and fluid in an electric potential. It demonstrate changes

in soil pH due to electrolysis reactions, water flow between the electrodes and migrate

ions towards the cathode (Keykha et al., 2012). This treatment has proved its

efficiency in consolidating oraganic, peat and clayey silt (Gingine et al., 2013). It is

also could be an attractive alternatives mechanism by introducing lime or other

desirable chemical compounds to the soil, in particularly when conventional mixing

is impossible for reasons of time constraints, access and depths (Jayasekera & Hall,

2007). According to Asavadorneja & Glawe (2005), electrokinetic stabilisation

method has been chosen as potentially the best method to give improvement of the

soft soil. It is also shows that EKS method can be less expensive than other method

otherwise this method also gave advantage by not disturbing site activities. Previous

study shows that there is a direct effect of electrolysis, transport and geochemical

changes under DC fields on the soil physical properties such as shear strength,

consolidation and swelling. Ionic grouting under DC fields is effective at increasing

the shear strength of soft soils. The process causes changes in the pH and ionic strength

3

profile across the electrodes that lead to development of a negative or positive pore

pressure (Alshawabkeh et al., 2004).

1.2 Problem statement

The growth of cities and industries, suitable sites, which can be used without some

ground modification, are becoming increasingly scarce. Additionally, the replacement

of soft soils with high quality materials are intensely expensive (Nguyen, Fatahi &

Khabbaz, 2014). In Southeast Asia soft clays are fairly widespread, and these deposits

exist extensively in the vicinity of capital cities. Most construction works has met

formidable obstacles (instability) when the construction area must built over the soft

clay deposits characterized by low undrained shear strength and high water contents.

Additionally, ground subsidence associated with the consolidation of soft clay

deposits correspondingly pose considerable threats to surface structures (Indraratna,

et al., 1992).

Soft soils and marine deposits are very common around the world. There are many

infrastructure projects and coastal high-rise buildings whose foundations are often

supported by such soils of low shear strength and high compressibility. The

construction of these projects on soft soils can lead to a very expensive foundation

system (Mohamedelhassan, 2011). These poor engineering properties of the soft clay

often pose foundation problems to structures. Due to high rapid of construction

activity, there is a necessity to improve the engineering properties of the soft clays and

accelerate the process of soil consolidation. Any construction cannot proceed before

the soil condition gains adequate bearing capacity (Micic et al., 2001). When the

application of traditional ground improvement techniques, such as surcharge, pre-

loading, wick drains, and vacuum pre-loading, is not appropriate for a particular

situation, innovative techniques such as EKS need to be considered (Jeyakanthan et

al., 2011).

There are various alternatives in dealing with problematic soils such as bypassing the

poor soil, replacing it superior soil, redesigning the structure for the poor condition or

improving the soil properties by mixing soil with material such as cement, lime,

4

gypsum and fly ash amongst other ground modification techniques. The latter option

can be used for surface improvement, such as road and rail subgrade improvement, or

in deep soil mixing or jet grouting technologies, which are soil improvement

approaches, mixing in situ soil with strengthening agents (Nguyen et al., 2014).

Conventional methods have been known successful in minimizing several damages,

however they are expensive, time-consuming and may be difficult to implement in

some existing structures (Mosavat et al., 2012). Obviously the damages came from

major settling or tilting of buildings, instability and road embankments.

Electrochemical or electrokinetic treatment method can be used as an alternative soil

treatment method for remediation of those deficiencies underneath building

foundations, roads, railways or pipelines. Furthermore, this technique involves an

approach with minimum disturbance to the surface while treating subsurface

contaminants and improving the engineering characteristics of subsurface soils

(Gingine et al., 2013).

Batu Pahat clay has a characteristic of low shear strength, and large compressibility

soil. EKS has been chosen to enhance the properties of Batu Pahat clay because this

method is applicable for fine grained soils and presence of clay particles in the low

permeable soils. Thus improvements for the soft clay are necessary as to improve the

poor subsurface soils before the construction works started. The stabiliser was fed at

anode and cathode compartments and this method involved applying a constant

voltage gradient to electrodes inserted into the low permeable soils.

1.3 Research aim and objectives

The aim of this study is to evaluate the use of EKS technique as an effective method

to strengthen Batu Pahat clay. The specific objectives for this study are;

i. To investigate the performance of EKS technique during laboratory

experiment towards Batu Pahat clay.

ii. To investigate physical parameters of Batu Pahat clay after treated with EKS

technique.

5

iii. To investigate chemical and mineralogical parameters of Batu Pahat clay after

treated with EKS technique.

iv. To investigate which combination of stabilisers are more effective in enhance

the strengthening of Batu Pahat clay amongst calcium chloride – distilled water

and calcium chloride – sodium silicate.

1.4 Scope of study

This research study was conducted in Research Centre for Soft Soils (RECESS) of

Faculty of Civil & Environmental Engineering (FKAAS), Universiti Tun Hussein Onn

Malaysia (UTHM). Batu Pahat clay has been used as the sample for EKS experiment.

EKS test rig was designed for this research study where it consisted of one main

compartment for soil sample and two small compartments for chemical stabilisers as

shown in Figure 3.4.

This study was conducted in two phases by using the different combination of

chemical stabilisers. For first phase of EKS experiment, it was performed by using 1.0

M of calcium chloride (CaCl2) solution that was fed at anode compartment and

distilled water (DW) was fed at the cathode compartment. While for second phase, the

test was performed by feeding 1.0 M of CaCl2 and sodium silicate (Na2SiO3) at the

anode and cathode compartment, respectively. EKS experiment was performed in 21

days period of time. Stainless steel plate was used as the electrodes and 50 V/m of

voltage gradient was applied to supply the current in this research study.

During the experiment, the test was monitored to ensure the consistency of applied

current from beginning until the end of experiment and also to ensure the volume of

stabilisers was sufficiently enough for the experiment. Furthermore, the experiment

was monitored for their pH of stabilisers, electric current and the amount of effluent

water discharged were recorded where the effluent volume was collected using

measuring cylinder. After EKS experiment through the soil sample ended, the treated

soil was investigated for their physical and chemical characteristic. Physical

characteristic of the treated soil was investigated. There were undrained shear strength,

Atterberg limit, and moisture content. While the chemical characteristic of the treated

6

soil was investigated for their mineralogy composition, metals ions concentration and

pH.

1.5 Significance of this study

EKS has shown the potential to enhance the ground and soil stability. Thus, it can be

one of the alternative way in ground improvement technology compared to the

conventional method. Furthermore it is possible to be applied in existing structures

where it coincidently could reduce in term of cost and time. Hence, EKS method might

fulfill client needed because this method are less time consuming and cost effective

compared to the conventional method.

Due to the potential of EKS in soil stabilisation, it was hoped that this method could

be developed and gave more benefits towards technology in many aspects such as cost

effectiveness, less time consuming, treatment flexibility, and environmental friendly.

Thus, it would allow a more rapid and efficient stabilisation works towards ground

and existing structure so that it can endure a higher imposed load in any circumstances.

An extensive study need to be undertaken, characterize and predict towards the

behavior of the clay, so that future structures can be designed and constructed safely

and economically.

7

CHAPTER II

LITERATURE REVIEW

2.1 Introduction

Recently, the number of research in finding an innovation and alternative way for the

efficient soil stabilisation were increased. This chapter narrate the process that

involves in EK and research gap including the data from previous study that related to

the EKS technique. It provides the relevant literature to enable a better understanding

that involves in EKS technique, there were clay mineralogy, physical and behavior of

clays, clay-water-electrolyte system, double layer theory, cation exchange,

electrokinetic phenomena and electrokinetic stabilisation.

2.2 Marine clay

Marine clay is uncommon type of clay and normally exists in soft consistency. Marine

clay was classified as clayey silt with low organic content (Rahman et al., 2013) and

found in the ocean bed (Basack & Purkayastha, 2009). Moreover, it can be found

onshore as well. Their properties rely on their initial conditions, where the saturated

marine clay soil are differ significantly from moist and dry soil. Marine clay is

microcrystalline in nature, as well as clay minerals and non-clay minerals are presents

in the soil. The clay minerals that contain in marine clay are chlorite, kaolinite and

illite while for non-clay minerals are quartz and feldspar.

8

Figure 2.1: Distribution of Cenozoic sediments in Peninsular Malaysia (after

Suntharalingam, 1983).

The distribution of Cenozoic sediments in Peninsular Malaysia were shown in Figure

2.1. The Cenozoic underlies slightly more than 20 percent of the land area of

Peninsular Malaysia of which the majority of the sediments are Quaternary age and it

shows the Batu Pahat clay was categorised in quaternary deposits. The four

stratigraphic units have been delineated on the bases of lighology, heavy mineral

content and to a lesser extent, on paleoenvironment. They are continental Simpang

Formation, Kempadang Formation, Gula Formation and the continental Beruas

9

Formation. The description of these units were explained in Table 2.1 (Suntharalingam,

1983);

Table 2.1: The stratigraphic units for quaternary deposits.

Formation Description

Simpang This unit is made up of gravel, sand, clay and silt overlying the

bedrock.

The formation is divided into two member; the lower sand

member which consist of sand and gravel and the upper layer

which is mainly clay.

The thickness varies from a few metres to more than 50 m and the

bulk of placer tin of Peninsular Malaysia is derived from lower

sand member.

Kempadang This unit made up of mainly marine clay with shells and sands.

Cassiterite has been recorded in the sand fraction.

Gula This formation is made up of mainly grey to greenish grey marine

to estuarine clay and subordinate sand.

The maximum thickness recorded is 20 m.

Beruas This unit consist of fluviatile – estuarine – lacustrine deposits mad

eup of clay, sandy clay, sandy gravel, silt and peat.

Figure 2.2: Location of marine clay deposits in Southern Region of Peninsular

Malaysia (after Indraratna, Balasubramaniam & Ratnayake, 1994).

10

A study by Indraratna, Balasubramaniam & Balachandran (1992) shows a coastal

plain marine clay up to 20 m thick was found along the west coast of Peninsular

Malaysia, with an average lateral extent of about 25 km. Where the site studies located

20 km from Muar and 50 km due east of Malacca on the southwest coast of Malaysia

as seen in Figure 2.2. It also showing the existence of a weathered crust of about 2.0

m thick above a 16.5 m thick layer of soft silty clay. The second layer of it was divided

into an upper very soft and a lower soft silty clay. There were also a 0.3 – 0.5 m thick

peaty soil followed by a stiff sandy clay found beneath the lower clay layer and at

about 22.5 m below ground level the succession ends at a dense sand layer.

A study by Taha, Ahmed & Asmirza (2000) clarify a research concerning the one-

dimensional consolidation of Klang clay, where the samples were taken near the Port

of Klang and it were divided into two clay layers. On the upper layer was marine clay

while on the lower layer was river clay. They are differentiated due to the existence of

corals and sea shells which is distinguished feature of the marine clay only occurred

in the upper deposits and none in the lower deposits. The colour of marine clay are

dark grey and this was possibly developed due to oxidation of sulphur and iron in the

clay as a result of it being exposed to atmosphere.

Table 2.2: Physical properties of marine clay from previous study.

Researcher Location Atterberg Limit

(%)

Cu

(kPa)

Gs w

(%)

LL PL PI

Rahman et al.,

(2013)

Kuala Muda,

Kedah

70 -

79

42 -

44

28 -

35

- 2.60 65.9

Basack &

Purkayastha

(2009)

Visakhapatnam,

India

89 47 42 - 2.62 -

Indraratna,

Balasubramaniam

& Balachandran

(1992)

Muar, Johor - - 40 -

50

8.0 - 100.0

Abdurahman

(2005)

Batu Pahat,

Johor

37 -

65

20 -

35

13 -

31

- 2.18-

2.65

-

Taha, Ahmed &

Asmirza (2000)

Port of Kelang,

Selangor

71 32 - - 2.64 71

11

(-) Not stated

Table 2.3: Chemical and mineralogical properties of marine clay from previous

study.

Researcher Location pH Organic

content

(%)

Mineral

composition

CEC

(meq/100g)

Rahman et al.,

(2013)

Kuala Muda,

Kedah

7.7 1.97 Montmorillonite,

kaolinite, illite,

quartz, halite

26.05

Basack &

Purkayastha

(2009)

Visakhapatnam,

India

7.2 7.00 Montmorillonite,

chlorite,

kaolinite,

vermicullite,

quartz

30.80

Indraratna,

Balasubramaniam

& Balachandran

(1992)

Muar, Johor - - Montmorillonite,

kaolinite, illite,

quartz

-

Taha, Ahmed &

Asmirza (2000)

Port of Klang,

Selangor

- - Montmorillonite,

illite, kaolinite,

kaolinite,

microline

-

(-) Not stated

2.3 Clay mineralogy

Clay mineralogy often explained by their size, shape and properties of the clay

particles. Different behavior of clay particles with respect to other constituent is

depends on the different ratio exist between the solid surface and their specific surface.

Specific surface results in strong influence of the electrical forces and the liquid solid

interface phenomena. It is also results in the bonding properties of clays and

association with a particular chemical structure in swelling characteristic. The smaller

the size of particles it will determine a smaller dimension of the pores (Ahmad Tajudin,

2012).

Clay is related to a size and to a classification of their minerals. It refer to all

constituent of a soil that smaller than 0.002 mm for size determination. While, specific

12

clay minerals is refer for mineral determination that are distinguished by small particle

size, a net negative electrical charge, plasticity when mixed with water and high

weathering resistance (Mitchell & Soga, 2005)

Clay minerals are complex aluminum silicates where it composed of two basic units;

silica tetrahedron and alumina octahedron. Every unit consists of four oxygen atoms

that surround the silicon atom (see Figure 2.3a). When the tetrahedral silica unit

combined each other, the combination produced a silica sheet (see Figure 2.3b). The

neighboring tetrahedral shared the three oxygen atoms at the base of each tetrahedron.

An aluminum atom surrounded by the octahedral unit which consist of six hydroxyls

(see Figure 2.3c), and when the octahedral aluminum hydroxyl unit combined each

other it produced an octahedral sheet (see Figure 2.3d). In certain cases, aluminum

atoms will replace by magnesium in the octahedral units hence this is called as brucite

sheet (Braja, 2007).

Figure 2.3: (a) Silica tetrahedron; (b) silica sheet; (c) alumina octahedron; (d)

octahedral (gibbsite) sheet (after Braja, 2007).

13

Each silicon atom with a positive charge of four is linked to four oxygen atoms in a

silica sheet with a total negative charge of eight and only the oxygen atom at the base

of the tetrahedron is linked to two silicon atoms. Hence, only the top oxygen atom of

each tetrahedral unit has a negative charge of one to be counterbalanced. The

hydroxyls replaced by oxygen atoms to balance their charges, it is when the silica

sheet is stacked over the octahedral sheet (Braja, 2007).

Kaolinite consists of three layers of elemental silica-gibbsite sheets in a 1:1 lattice,

(see Figure 2.4a); and each layer is about 7.2 Å thick a held together by hydrogen

bonding. It has a lateral dimension of 1000 to 20,000 Å and a thickness of 100 to 1000

Å. The surface area of these particles is about 15 m2/g and it is defined as specific

surface (Braja, 2007).

From Figure 2.4b shows the illite’s structures diagram and it is consist of a gibbsite

sheet bonded to two silica sheets where one at the top and another at the bottom. These

layers are bonded by potassium ions. Negative charge will balanced the potassium

ions that come from the substitution of aluminum for silicon in the tetrahedral sheets.

The range lateral dimension for illite is from 1000 to 5000 Å and thickness from 50 to

500 Å. Specific surface for illite is about 80 m2/g (Braja, 2007).

While for montmorillonite the structures diagram seems similar to that of illite (see

Figure 2.4c). There is isomorphous substitution of magnesium and iron for aluminum

in the octahedral sheets. The range lateral dimension for montmorillonite is from 1000

to 5000 Å and thickness of 10 to 50 Å. Specific surface for montmorillonite is about

800 m2/g (Braja, 2007).

14

Figure 2.4: Diagram of the structures of (a) kaolinite; (b) illite; (c) montmorillonite

(after Braja, 2007).

2.4 Engineering properties of clay minerals

Each group of clay mineral posses a wide range of engineering properties. Basically,

the engineering properties of clay minerals includes particle size, degree of

crystallinity, type of adsorbed cations, pH, the presence of organic matter, and the type

and amount of free electrolyte in the pore water. Generally, these factors increases in

the order kaolin < hydrous mica (illite) < smectite. Chlorite will exhibit characteristics

in the kaolin – hydrous mica range. While, for vermiculites and attapulgite have

properties that usually fall in the hydrous mica – smectite range (Mitchell & Soga,

2005). According to Liaki, Rogers & Boardman (2010), an improvement of the

engineering properties of soft clay can be accomplished by water content reduction

and the addition of stabilising chemicals.

A study by Du et al., (2014), clarify the details of a study that deals with determination

of engineering properties of a zinc-contaminated kaolin clay where it were stabilised

with a cement additive. It were carried out towards the effects of the level of zinc (Zn)

15

concentration on the overall soil properties. Additionally, X-ray diffraction, scanning

electron microscopy and mercury intrusion porosimetry studies were performed to

investigate the mechanisms that controlling the changes in engineering properties of

stabilised kaolin clay. It reveals that the level of Zn concentration significantly

influenced the engineering properties, phases of hydration products formed and

microstructural characteristics of the stabilised kaolin clay. The results are attributed

to the retardant effect of Zn on the hydration and pozzolanic reactions, hence it will

alters the phases of hydration products and cementing structure – bonding of the soils.

2.5 Physical chemistry of clays

The combination of the high surface area and the electrical charge in the silicate

structure of the clay mineral results in the unusual physicochemical properties of clay.

High surface area is effect from the small particle size and platy or elongate

morphology of the minerals and the negative charge from ionic substitutions in the

crystal structure. The charge in the silicate structure will occur as discrete charge rather

than as a uniform distribution over the surface (Ahmad Tajudin, 2012).

The clay particles showing the properties characteristic of the colloidal state when the

size within the range of about 50 to 2000 Å. The distinctive physicochemial properties

results from the surfaces of the materials. No imbalance in the forces acting on the

atoms in the interior of a solid, liquid or gas which are surrounded on all sides by a

similar configuration of atoms. The attractive forces most strongly pulled the surfaces

atoms of a solid or liquid on the side facing inward (Ahmad Tajudin, 2012).

The properties for colloidal suspension which are different from those of either a true

solution or a suspension of coarser particles (Ahmad Tajudin, 2012);

The colloidal suspension will pass through filter paper.

It presents the electrical effects such as electrophoresis and electroosmosis.

The particles are recognizable in the ultra-microscope.

The particles possibly will affected frequently to precipitate of “flocculate” by

the addition of small amounts of electrolytes.

16

The whole system possibly will specified forming gel, the process were

identified as gelation.

According to Liaki, Rogers & Boardman (2010), it is difficult to predict the

physicochemical changes in clay soils with accuracy due to the application of

electrokinetic because of the very wide range of parameters interacting. A study by

Liaki et al., (2010), presents the details of a study towards the effect of the application

of an electrical gradient across controlled specimens of a pure form of kaolinite by

using stainless steel electrodes and deionised water feed to electrodes. The treated

samples over different time periods (3,7, 14 and 28 days) were then tested for

Attereberg limits, undrained shear strength, water content, pH, conductivity, Fe

concentration and zeta potential. The results shows changes in strength and plasticity

indices. The changes were attributed to electrolysis, electroosmosis, electrode

degradation, clay mineral dissolution, ion movement due to electromigration, cation

exchange reaction and precipitation of reaction products.

2.6 Clay-water-electrolyte system

Mitchell & Soga (2005) specified that basically clays are lyophobic (liquid hating) or

hydrophobic (water hating) colloids rather than lyophilic or hydrophilic colloids, even

though water wet clays and is adsorbed on particle surfaces. Thus, it results to

distinguish colloids such as gums where’s exhibit such an affinity for water that they

spontaneously form a colloidal solution. Hydrophobic colloids are liquid dispersions

of small, solid particles that are;

Two-phase system with a large interfacial surface area

Have a behavior dominated by surface forces

Can flocculate in the presence of small amounts of salt

Clay-water-electrolyte systems satisfy all of the criteria as states above (Mitchell &

Soga, 2005).

2.7 Ion distribution in clay-water systems

17

Basically on the surfaces of negatively charged dry clay particles the adsorbed cations

are tightly held on it. The salt precipitates resulted from the cations in excess of those

needed to neutralize the electronegativity of clay particles and associated anions. The

precipitates across into the solution when the water is exist. High concentration near

the surfaces of particles of the adsorbed cations will diffuse away in order to equalize

concentrations through the pore fluid. Somehow it is restricted by the negative

electrical field originating in the particle surfaces and ion-surface interactions that are

unique to specific cations (Mitchell & Soga, 2005).

Figure 2.5: Distribution of ions adjacent to a clay surface according to the concept of

the diffuse double layer (after Mitchell & Soga, 2005).

Figure 2.5 shows the escaping tendency due to diffusion and the opposing electrostatic

attraction lead to ion distribution adjacent to a single clay particle in suspension. This

distribution of cations is analogous to that of air molecules in the atmosphere, where

the escaping tendency of the gas is countered by the gravitational attraction of earth.

The anion will exclude from the negative force fields of the particles with the

distribution as shown in the figure above (Mitchell & Soga, 2005).

2.8 Diffuse double-layer theory

18

Barker et al., (2004) explained that clays are consists of small particles (

19

Figure 2.6: The Helmholtz electric double layer (after Altaee, 2004).

The thicker diffuse layer will affect the tendency for particles in suspension to

flocculate and higher swelling pressure in expensive soils. The diffuse layer become

thinner when the electrolyte concentration is increase, hence it will reduce the surface

potential for the condition of constant surface charge and the decay of potential with

distance is much more rapid. The flocculation of particle in suspension resulted from

the consequence of the phenomena when facilitated by an increase in electrolyte

concentration. Thus, the electrolyte concentration will affect the swelling behavior of

clay (Ahmad Tajudin, 2012).

20

Figure 2.7: Stern’s model and ions distribution in the electric double layer (after

Hiemenz, 1977).

The mid-plane concentrations and potential between interacting plates effects from the

increasing in cation valence, hence it leads to a decrease in interplate repulsion.

Adsorbed multivalent ions usually restrict the separation distance between clay

platelets, consequently resulting in a limited applicability of the double layer equations

(Mitchell & Soga, 2005).

2.9 Soil surface charge

The two types for soil surface charge are permanent charge and pH dependant charge.

The total soil surface charge is similar with the sum of both charges. The soil

permanent charge results from the isomorphous substitution within the clay lattice.

The soil surface developed a net negative charge when an ion of higher positive charge

21

is replaced by an ion of lower positive charge and the charge is permanent (Altaee,

2004).

The dissociation of hydroxyl groups of silica, iron oxides and alumina produced the

pH dependent soil charge. The process are subject of many factors such as soil pH,

electrolyte concentration and ion species involved. This charged is directly related to

the soil pH and occurs at the surfaces and on the edges of clay minerals, hence more

disordered the clay surface structure affect the charge.

The dissociation of carboxyl groups in organic matter leads to the soil negative charge.

The extent of dissociation is strongly dependant on the nature of the organic polymer,

soil pH, electrolyte concentration, and cation chemical species. Mostly, the soils have

negative charge due to the negative charges of layer silicates and organic matter. Low

pH will developed a net positive charge in highly weathered soils dominated by

hydrous oxides (Altaee, 2004).

2.10 Cation exchange

The clay adsorbs cations of specific types and amounts under a given set of

environmental conditions including the temperature, pressure, pH, chemical and

biological composition of the water. The charge deficiency of the solid particles

balanced by the total amount adsorbed. A response to changes in the environmental

conditions held when exchange reactions occur. These reaction consist the

replacement of a part or all of the adsorbed ions of one type by ions of another type.

The important changes in the physical and physicochemical properties of the soil may

result although the exchange reactions do not ordinarily affect the structures of the

clay particles (Mitchell & Soga, 2005).

Different samples of the same clay mineral resulted the different values for cation

exchange capacity. Hence a range of values exist for the same mineral due to the

differences in structure and composition between the samples. It shows that the

particle size of clay gave an important effect (Ahmad Tajudin, 2012).

22

The major source of clay exchange capacity is isomorphous substitution except for

kaolin mineral. For clay minerals, certain tetrahedral and octahedral spaces are

occupied by cations other than those in the ideal structure. It also causes the clay

minerals to obtain a net negative charge that resulted from isomorphous substitution.

The cations are attracted and held between the layers and on the surfaces and edges of

the particles to preserve electrical neutrality. These cations are exchangeable cations

because they may replace by cations of different type (Mitchell & Soga, 2005).

The broken bond due to unsatisfied valencies at edges and corners to which exchange

ions become attached is the second major source of clay exchangeable capacity. When

the particle size decreases the number of exchange site will increases and fine fractions

of many minerals show an increase in exchange capacity. This effect is shown by

kaolinite and contributes up to 20 percent of the total in smectite (Mitchell & Soga,

2005).

Another source of clay exchangeable capacity is replacement of the hydrogen of an

exposed hydroxyl by another type of cation. The structure may become exchangeable

under certain condition actions from within. The contribution of these sources depends

on various environmental and compositional factors, hence a given clay minerals does

not have a fixed, single value of exchange capacity. The capacity is directly related to

the specific surface and surface charge density (Ahmad Tajudin, 2012).

Porbaha (1998) stated the three major categories of reaction that was expected from

the process of mixing a stabiliser with clay, there were dehydration process, ion

exchange or flocculation and pozzolanic reaction.

2.10.1 Ion Selectivity

Sodium, potassium, calcium, magnesium and lithium were usually the types of cations

that normally found in the diffuse double layer and the pore water. The higher valency

or larger ionic radius cations that introduced in significant concentrations for example

calcium, silicon or aluminium, they will saturated the solution and become adsorbed

23

at the clay surface in preference to those ions originally presents. The cation exchange

generally occurred in two reasons, there are (Barker et al., 2004);

i. Ions in greater concentration will replace those of a lower concentration

ii. The lytropic series normally states that the higher valence cations replace those

of a lower valence and the larger cations replace smaller cations of the same

valence. The lytropic series is written as:

Na+ < Li+ < K+ < Rb+ < Cs+ < Mg2+ < Ca2+ < Ba2+ < Cu2+ < Al3+ < Fe3+ < Th4+

Those series illustrates the cations that to the right will preferentially replace those to

the left. The cations such as Ca2+ and Al3+ will replace the cations that commonly

found in clays. In example of the addition of lime or calcium ion, the cation exchange

resulting in reduction in the thickness of the layers where it allow a closer contact

between the clay platelets. This will promotes edge-to-face attraction or flocculation

hence resulting in changes in the soil’s workability, permeability, plasticity and swell

properties (Barker et al., 2004).

Figure 2.8: Flocculation of clay platelets parallel arrangement of clay particles with

hydrated water layer (after Barker et al., 2004).

24

Figure 2.9: Flocculation of clay platelets edge-to-face attraction induced by thin

water layer, which allows attractive forces to dominate (after Barker et al., 2004).

2.10.2 Pozzolanic reaction

The strength of soils will increase depending on the stabilisation mechanism which

were ion exchanges and pozzolanic reaction. The application of calcium ions as

stabilising agents towards the soil lead the process of ion exchanges of calcium ions

and monovalent ions in soils hence caused of the flocculation and coagulation of soil

particles into larger colloids. Chemical reaction between calcium and silicates or

aluminates under alkaline conditions resulted of pozzolanic reaction, henceforth leads

to the formation of cementing agents. The formation of it consisting of calcium silicate

hydrate (CSH) and also calcium aluminate hydrate (CAH) and the new pozzolanic

products are developed that bind together the clay particles to produce a stronger soil

matrix (Asavadorndeja & Glawe, 2005; Raftari et al., 2014). The secondary

pozzolanic recation also termed as solidification, it occurs once the pore chemistry in

soil system achieves a sufficiently alkaline condition and when sufficient

concentration of OH- ions is present in the pore water due to the hydrolysis of the lime

(Xiao & Lee, 2008).

112

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