UTILIZATION OF STEEL SLAG FOR STABILIZATION OF A LATERITIC SOIL
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 ” 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 “ 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.
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 ” 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 “ 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.
LIST OF FIGURES
Figure 2.1: Types of Slag 7
Figure 2.2: Types of Ferrous Slag 8
Figure 2.3: Flow of Steel Slag Production (Nippon Slag Association, 2006) 10
Figure 2.4: Major Productive Use of Steel Slag in Europe 11
Figure 2.5: Steel Slag Utilization in Europe 11
Figure 2.6: A Typical BOF (National Slag Association, 2011) 14
Figure 2.7: Schematic of Operational Steps in Oxygen Steelmaking Process (BOF) (Fruehan, 1998) 15
Figure 2.8: Typical Composition after Sampling (Corus, 2011) 17
Figure 2.9: A Typical EAF (National Slag Association, 2011) 18
Figure 2.10: Schematic of Operational Steps in EAF Processes (Corus, 2011) 19
Figure 3.1: Steel Slag Sample Collection Site 34
Figure 3.2: Lateritic Soil Sample Collection Site 34
Figure 4.1: Particle Size Distribution of Soil 42
Figure 4.2: Variation of Specific Gravity with Slag Content 42
Figure 4.3: Variation of Average Liquid Limit with Slag Content 42
Figure 4.4: Variation of Plastic Limit with Slag Content 44
Figure 4.5: Variation of Plasticity Index with Slag Content 45
Figure 4.6: Variation of OMC with Slag Content 46
Figure 4.7: Variation of MDD with Slag Content 46
Figure 4.8: Variation of Unsoaked CBR with Slag Content 47
Figure 4.9: Variation of Soaked CBR with Slag Content 48
Figure 4.10: Variation of Swell Potential with Slag Content 48
Figure 4.11: Variation of Unconfined Compressive Strength with Slag Content 50
Figure 4.12: Variation of Undrained Shear Strength with Slag Content 50
Figure 4.13: Variation of Permeability with Slag Content 51
Figure 2.1: Types of Slag 7
Figure 2.2: Types of Ferrous Slag 8
Figure 2.3: Flow of Steel Slag Production (Nippon Slag Association, 2006) 10
Figure 2.4: Major Productive Use of Steel Slag in Europe 11
Figure 2.5: Steel Slag Utilization in Europe 11
Figure 2.6: A Typical BOF (National Slag Association, 2011) 14
Figure 2.7: Schematic of Operational Steps in Oxygen Steelmaking Process (BOF) (Fruehan, 1998) 15
Figure 2.8: Typical Composition after Sampling (Corus, 2011) 17
Figure 2.9: A Typical EAF (National Slag Association, 2011) 18
Figure 2.10: Schematic of Operational Steps in EAF Processes (Corus, 2011) 19
Figure 3.1: Steel Slag Sample Collection Site 34
Figure 3.2: Lateritic Soil Sample Collection Site 34
Figure 4.1: Particle Size Distribution of Soil 42
Figure 4.2: Variation of Specific Gravity with Slag Content 42
Figure 4.3: Variation of Average Liquid Limit with Slag Content 42
Figure 4.4: Variation of Plastic Limit with Slag Content 44
Figure 4.5: Variation of Plasticity Index with Slag Content 45
Figure 4.6: Variation of OMC with Slag Content 46
Figure 4.7: Variation of MDD with Slag Content 46
Figure 4.8: Variation of Unsoaked CBR with Slag Content 47
Figure 4.9: Variation of Soaked CBR with Slag Content 48
Figure 4.10: Variation of Swell Potential with Slag Content 48
Figure 4.11: Variation of Unconfined Compressive Strength with Slag Content 50
Figure 4.12: Variation of Undrained Shear Strength with Slag Content 50
Figure 4.13: Variation of Permeability with Slag Content 51
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