UTILIZATION OF STEEL SLAG FOR STABILIZATION OF A LATERITIC SOIL

UTILIZATION OF STEEL SLAG FOR STABILIZATION OF A LATERITIC SOIL

ABSTRACT

According to the Unified Soil Classification System (USCS) and the AASHTO classification system, a lateritic soil categorized as sandy clay or (CL) and A-7-6 (5) was treated with up to 10% crushed steel slag (an industrial waste product) by dryweight of soil. X-ray fluorescence spectroscopy was used to assess the elemental and chemical composition of the steel slag. The natural and modified soils were tested for 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. Atterberg limits (liquid limit, plastic limit, and plasticity index) generally dropped, although specific gravity of soil ” steel slag combinations increased; MDD and OMC increased and reduced, respectively, with larger steel slag concentration. In general, CBR and UCS boosted soil steel slag treatment by up to 8%. The permeability of soil “steel slag combinations increased as the steel slag percentage rose. According to testing data, an 8% ideal stabilization of A-7-6 soil with steel slag meets the Federal Republic of Nigerian General Specifications (Roads and Bridges) standard for subgrade materials.

Section I: Table of Contents

CERTIFICATION, DEDICATION, AND ACKNOWLEDGEMENTS iv LIST OF FIGURES viii LIST OF TABLES ix LIST OF ACRONYMS AND ABBREVIATIONS x ABSTRACT xi

INTRODUCTION TO CHAPTER ONE 1.1 PREAMBLEMENT 1 1.2 Problem Description 1 1.3 Study Justification 2 1.4 Aims and Objectives 3 1.5 Scope of the Study 3 1.6 Importance of the Study 4

LITERATURE REVIEW 6 2.1 Background 6 2.2 What is Slag? 7 2.2.1 Slag Recycling 10 2.2.2 Slag Product Utility and Usage 11 2.3 Slag Utilization Efforts 13 2.4 Steel Slag Production 13

2.4.1 Basic Oxygen Steelmaking Slag 14 2.4.2 EAF Slag 17

2.4.3 Utilization of Steel Slag 19

2.5 Steel Slag Properties 20

2.5.1 Mechanical and Physical Properties 20

2.5.2 Mineralogical and Chemical Properties 23

2.6 Environmental and Health Issues 27

Soils with Laterite and Lateritic Composition 27

2.8 Lateritic Soil Stabilization 30

MATERIALS AND METHODS 33 CHAPTER THREE

3.1 Preparation and Materials 33

Steel slag 33 3.1.2 Soil 33

3.2 Methods 34 3.2.1 Steel slag chemical composition 36 3.2.2 Natural moisture content 36 3.2.3 Sieve analysis 37

3.2.4 Specific gravity 38 3.2.5 Atterberg limits 36 3.2.6 Compaction properties 39 3.2.7 Strength properties 38 3.2.8 Permeability 39

RESULTS AND DISCUSSION IN CHAPTER FOUR 40

41 4.1 X-ray Fluorescence

41.4.2 Natural Soil

41 4.3 Sieve Analysis

42 Specific Gravity

43 Atterberg Limits

4.6 Lateritic Soil Sample Compaction Characteristics 45

California Bearing Ratio 47 4.7

Unconfined Compressive Strength 49 4.8

51 Permeability 4.9

4.10 Best Stabilization 52

CONCLUSION AND RECOMMENDATIONS IN CHAPTER FIVE 53

5.1 Summary 53

5.2 Suggestions 54 REFERENCES 55 LABORATORY RESULT SHEETS 61

LIST OF IMAGES

Figure 2.1: Slag Types Figure 2.2: Different Types of Ferrous Slag Figure 2.3: Steel Slag Production Flow (Nippon Slag Association, 2006). Figure 2.4: Major Productive Applications of Steel Slag in Europe Figure 2.5 shows the use of steel slag in Europe. Figure 2.6: An Example of a BOF (National Slag Association, 2011) Figure 2.7: Operational Steps in the Oxygen Steelmaking Process (BOF) (Fruehan, 1998). Figure 2.8: Typical Sample Composition (Corus, 2011) Figure 2.9: An Example of an EAF (National Slag Association, 2011) Figure 2.10: Operational Steps in EAF Processes (Corus, 2011). Figure 3.1: Location of Steel Slag Sample Collection 34

Site 34 for Collecting Lateritic Soil Samples

Figure 4.1: Soil Particle Size Distribution 42

Figure 4.2: Specific Gravity Variation with Slag Content 42

Figure 4.3: Average Liquid Limit Variation with Slag Content 42

Figure 4.4: Plastic Limit Variation with Slag Content 44

Figure 4.5: Plasticity Index Variation with Slag Content 45 Figure 4.6: OMC Variation with Slag Content 46

Figure 4.7: MDD Variation with Slag Content 46

Figure 4.8: Unsoaked CBR Variation with Slag Content 47

Figure 4.9: Soaked CBR Variation with Slag Content 48

Figure 4.10: Swell Potential Variation with Slag Content 48

Figure 4.11: Unconfined Compressive Strength Variation with Slag Content 50

Figure 4.12: Undrained Shear Strength Variation with Slag Content 50

Figure 4.13: Permeability Variation with Slag Content 51

TABLES IN ORDER

Table 2.1: Typical Applications of Slag in Civil Engineering (National Slag Assoc., 2011) 12

Table 2.2: Event Times for Basic Oxygen Steelmaking (Fruehan, 1998). 16

Table 2.3: Steel Slag Applications (Nippon Slag Association, 2006) 20

Table 2.4: Physical Properties of Typical Steel Slag 21

Table 2.5: Results of Particle Size Distribution for BOF and EAF Slags 22

Table 2.6: Mechanical Properties of Typical Steel Slag 22

Table 2.7: Metal Concentration Range in BOF and EAF Slags 24

Table 2.8: Chemical Composition of Typical Steel Slag 25

Table 2.9: Chemical Composition of Steel Slag and Portland Cement 27

Table 2.10: Lateritic Soil Properties (Okafor and Okonkwo, 2009) 30

XRF Analysis of Steel Slag Sample 40 (Table 4.1)

Table 4.2: Natural Soil Geotechnical Properties 41

Table 4.3: Optimal Stabilization Geotechnical Properties 52

AASHTO is an abbreviation for the American Association of State Highway and Transportation Officials.

ASTM stands for American Society for Testing and Materials.

Basic Oxygen Furnace slag (BOF) British Parameters

CBR Bearing Ratio in California

EAF Electric Arc Furnace slag CERD Centre for Energy and Research Development

Human Health and Environmental Risk Assessment (HERA)

LL MDD Liquid Limit Dry Density Maximum

OMC OSC Optimum Steel-slag Content PI Plasticity Index PL Plastic Limit OSC Optimum Moisture Content

SEM stands for Scanning Electron Microscope.

SSC UCS Steel Slag Coalition USC Unified Soil Classification System XRD X-ray Diffraction XRF X-ray Fluorescence XRF X-ray Fluorescence