Preface ..- .. v 1. Introduction ..- .. 1 1.1 General ..- 1 1.2 Coal- 2 1.3 Coal Ash Production 4 1.4 Handling and Disposal of Coal Ashes.. 5 1.5 Coal Ash Utilisation 8 1.6 Summary ..- .. 9 2. Chemical Properties 10 2.1 Chemical Composition.. 10 2.2 X-ray Diffraction Spectra and Morphology 17 2.3 pH of Coal Ashes .. 21 2.4 Lime Reactivity 23 2.5 Cation Exchange Capacity .. 25 2.6 Summary ..- 25 3. Physical Properties 26 3.1 Specific Gravity 26 3.2 Grain Size Distribution .. 32 3.3 Coal Ashes and Consistency Limits .. 38 3.3.1 General . 38 3.3.2 K0-stress Method for Coal Ashes .. 39 3.4 Free Swell Index (FSI) 41 3.5 Specific Surface 42 3.6 Classification of Coal Ashes 44 3.6.2 Geotechnical Classification System for Coal Ashes 47 3.7 Summary ..- 52 4. Engineering Properties . 54 4.1 Compaction Characteristics 54 4.1.1 Introduction 54 4.1.2 Compaction Curves of Coal Ashes. 56 4.1.3 Effect of Delay Between Mixing and Compaction .. 67 4.2 Compressibility and Consolidation Characteristics 67 4.2.1 Introduction 67 4.2.2 Compressibility..- ..69 4.2.3 Consolidation Characteristics .. 71 4.2.4 Secondary Consolidation 73 4.2.5 Collapse Behaviour.. 73 4.3 Permeability Characteristics 76 4.4 Strength Characteristics 79 4.4.1 General . 79 4.4.2 Unconflned Compressive Strength 82 4.4.3 Shear Strength From Direct Shear Box Test 85 4.4.4 Shear Strength From Triaxial Shear Tests .. 89 4.4.5 Angle of Repose .. 91 4.5 California Bearing Ratio (CBR). 94 4.6 Dispersiveness 95 4.6.1 Double Hydrometer Test 96 4.6.2 Pin Hole Test 97 4.6.3 Turbidity Test 97 4.7 Leaching Behaviour 98 4.8 Summary ..- 98 5. Coal Ash/Soil Stabilisation .. 99 5.1 General ..- .. 99 5.2 Fly Ash Stabilisation 100 5.2.1 Control of Unburned Carbon Content and Coarser Particles in Fly Ash.. 100 5.2.2 Lime/Cement Stabilisation of Coal Ashes . 101 5.2.3 Fly Ash Stabilisation With Fine-grained Soil as an Admixture .. 102 5.3 Soil-Fly Ash Mixtures .. 105 5.3.1 Index Properties. 105 5.3.2 Engineering Properties 105 5.4 Use of Fly ash in the Field 119 5.5 Summary ..- .. 120 6. Concluding Remarks.. 121 6.1 The Positives . 121 6.2 Limitations and the Remedy .. 124 6.3 The Need ..- 126 References ..- 127 Author Index..- .. 133 Subject Index..- . 135