UTILIZATION OF STEEL SLAG FOR STABILIZATION OF A LATERITIC SOIL

By

Isaac Ibukun Akinwumi (CUGP080208)

Presented To

Department of Civil Engineering

ABSTRACT
A lateritic soil classified as sandy clay or (CL) and A-7-6 (5) according to Unified Soil Classification System (USCS) and AASHTO classification system respectively,was treated with up to 10% pulverized steel slag (an industrial waste product) by dryweight of soil. Elemental and chemical analysis of the steel slag was determined using x-ray fluorescence spectroscopy. Tests were carried out to determine the index properties, compaction characteristics (maximum dry density, MDD and optimum moisture content, OMC), strength characteristics (California bearing ratio, CBR and unconfined compressive strength, UCS) and permeability of the natural and treated soil. Test results show that Atterberg limits (liquid limit, plastic limit and plasticity index)
generally decreased, while specific gravity of soil â€" steel slag mixtures increased with higher steel slag content; MDD and OMC increased and decreased, respectively, with higher steel slag content. Generally, CBR and UCS increased up to 8% steel slag treatment of the soil. Permeability of soil â€" steel slag mixtures increased with higher steel slag content. Based on laboratory test results, an 8 % optimal stabilization of the A-7-6 soil with steel slag satisfactorily meets the Federal Republic of Nigerian General Specifications (Roads and Bridges) requirement for subgrade materials.

Table of Contents
CERTIFICATION ii
DEDICATION iii
ACKNOWLEDGEMENTS iv
LIST OF FIGURES viii
LIST OF TABLES ix
LIST OF ABBREVIATIONS AND ACRONYMS x
ABSTRACT xi

CHAPTER ONE
INTRODUCTION
11 Preamble 1
12 Statement of the Problem 1
13 Justification for the Study 2
14 Aim and Objectives 3
15 Scope of the Study 3
16 Significance of Study 4

CHAPTER TWO
LITERATURE REVIEW 6
21 Background 6
22 What is Slag? 7
221 Slag Recycling 10
222 Utility and Usage of Slag Products 11
23 Efforts in Utilizing Slag 13
24 Production of Steel Slag 13
241 BOF Slag from Basic Oxygen Steelmaking 14
242 EAF Slag 17
243 Steel Slag Utilization 19
25 Properties of Steel Slag 20
251 Physical and Mechanical Properties 20
252 Chemical and Mineralogical Properties 23
26 Environmental and Health Considerations 27
27 Laterite and Lateritic Soils 27
28 Stabilization of Lateritic Soils 30

CHAPTER THREE
MATERIALS AND METHODS 33
31 Materials and Preparation 33
311 Steel slag 33
312 Soil 33
32 Methods 34
321 Chemical composition of steel slag 36
322 Natural moisture content 36
323 Sieve analysis 37
324 Specific gravity 38
325 Atterberg limits 36
326 Compaction characteristics 39
327 Strength characteristics 38
328 Permeability 39

CHAPTER FOUR
RESULTS AND DISCUSSION 40
4 1 X-ray Fluorescence 41
42 Natural Soil 41
43 Sieve Analysis 41
44 Specific Gravity 42
45 Atterberg Limits 43
46 Compaction Characteristics of Lateritic Soil Sample 45
47 California Bearing Ratio 47
48 Unconfined Compressive Strength 49
49 Permeability 51
410 Optimal Stabilization 52

CHAPTER FIVE
CONCLUSION AND RECOMMENDATION 53
51 Conclusion 53
52 Recommendation 54
REFERENCES 55
APPENDIX: LABORATORY RESULT SHEETS 61

LIST OF FIGURES
Figure 21: Types of Slag 7
Figure 22: Types of Ferrous Slag 8
Figure 23: Flow of Steel Slag Production (Nippon Slag Association, 2006) 10
Figure 24: Major Productive Use of Steel Slag in Europe 11
Figure 25: Steel Slag Utilization in Europe 11
Figure 26: A Typical BOF (National Slag Association, 2011) 14
Figure 27: Schematic of Operational Steps in Oxygen Steelmaking Process (BOF) (Fruehan, 1998) 15
Figure 28: Typical Composition after Sampling (Corus, 2011) 17
Figure 29: A Typical EAF (National Slag Association, 2011) 18
Figure 210: Schematic of Operational Steps in EAF Processes (Corus, 2011) 19
Figure 31: Steel Slag Sample Collection Site 34
Figure 32: Lateritic Soil Sample Collection Site 34
Figure 41: Particle Size Distribution of Soil 42
Figure 42: Variation of Specific Gravity with Slag Content 42
Figure 43: Variation of Average Liquid Limit with Slag Content 42
Figure 44: Variation of Plastic Limit with Slag Content 44
Figure 45: Variation of Plasticity Index with Slag Content 45
Figure 46: Variation of OMC with Slag Content 46
Figure 47: Variation of MDD with Slag Content 46
Figure 48: Variation of Unsoaked CBR with Slag Content 47
Figure 49: Variation of Soaked CBR with Slag Content 48
Figure 410: Variation of Swell Potential with Slag Content 48
Figure 411: Variation of Unconfined Compressive Strength with Slag Content 50
Figure 412: Variation of Undrained Shear Strength with Slag Content 50
Figure 413: Variation of Permeability with Slag Content 51

LIST OF TABLES
Table 21 Typical Use of Slag in Civil Engineering Applications (National Slag Ass,
2011) 12
Table 22: Basic Oxygen Steelmaking Event Times (Fruehan, 1998) 16
Table 23: Applications of Steel Slag (Nippon Slag Association, 2006) 20
Table 24: Typical Physical Properties of Steel Slag 21
Table 25: Particle Size Distribution Results for BOF and EAF Slags 22
Table 26: Typical Mechanical Properties of Steel Slag 22
Table 27: Range of Metal Concentration in BOF and EAF Slags 24
Table 28: Typical Chemical Composition of Steel Slag 25
Table 29: Comparison of Chemical Comp of Steel Slag and Portland Cement 27
Table 210: Properties of a Lateritic Soil (Okafor and Okonkwo, 2009) 30
Table 41: XRF Result of Steel Slag Sample 40
Table 42: Geotechnical Properties of Natural Soil 41
Table 43: Some Geotechnical Properties at Optimal Stabilization 52

LIST OF ABBREVIATIONS AND ACRONYMS
AASHTO American Association of State Highway and Transportation Officials
ASTM American Association for Testing and Materials
BOF Basic Oxygen Furnace slag
BS British Standards
CBR California Bearing Ratio
CERD Centre for Energy and Research Development
EAF Electric Arc Furnace slag
HERA Human Health and Ecological Risk Assessment
LL Liquid Limit
MDD Maximum Dry Density
OMC Optimum Moisture Content
OSC Optimum Steel-slag Content
PI Plasticity Index
PL Plastic Limit
SEM Scanning Electron Microscope
SSC Steel Slag Coalition
UCS Unconfined Compressive Strength
USC Unified Soil Classification System
XRD X-ray Diffraction
XRF X-ray Fluorescence