Experimental Study on the Stabilization of Fine Grained Soils by Steel Furnace Slag and Lime for Using as Subbase Material

In this study, an attempt was made to stabilize a plastic, fine-grained soil using steel furnace slag (SFS) and lime for use as subbase materials in pavements. Different amounts of SFS (0, 10, 20, and 30%) and hydrated lime (0, 2, 4, and 6%) were used to stabilize the geotechnical properties of the soil. The effects of SFS and lime were experimentally investigated through physical and mechanical tests, including plasticity limits, compaction, unconfined compressive strength (UCS), and CBR tests. The stabilized soil specimens were cured for 28 days. The test results showed that as the SFS and lime contents increased, the soil's maximum dry density (MDD), UCS, and CBR values also increased, while the optimum moisture content (OMC) and plasticity index (PI) decreased. The UCS results suggested that the appropriate amount of SFS for stabilizing the plastic, fine-grained soil was more than 30%. It appears that when the amount of slag was less than 30%, the slag particles were surrounded by fine materials and the contacts between slag particles were not dominant. Taking both CBR and UCS into consideration, a lime content of 4% was determined to be the optimum amount for stabilizing the plastic, fine-grained soil. XRD and SEM analysis of a stabilized sample suggests the formation of cementitious phases highlight the interactions between the soil and additives. The experience of soil improvement on site has shown that it is better to use SFS along with lime to stabilize plastic, fine-grained soils, especially in sulfate soils.