Experimental study on physical and mechanical properties of expanded soil improved by lime activated blast furnace slag

Abstract To address environmental concerns related to cement-stabilized expansive soil and the safety risks of caustic-activated blast furnace slag, this study explores the use of lime-activated blast furnace slag as an alternative stabilizer in northern Hebei, China. The effects of slag dosage, curing time, and osmotic pressure on the expansion, osmotic properties, and strength of the improved soil were evaluated through free expansion rate, permeability coefficient, and unconfined compressive strength tests. Results show that adding slag-lime significantly reduces soil expansion. As slag content increases, the free expansion rate decreases exponentially. During the curing period of 3–7 days, expansion declines and stabilizes between 7–14 days. Similarly, the permeability coefficient permeability coefficient decreases with higher slag content, following a quadratic trend. Under osmotic pressures of 0.1–0.2 MPa, the permeability coefficient permeability coefficient increases but stabilizes between 0.2–0.4 MPa.Furthermore, slag-lime significantly enhances unconfined compressive strength, which increases linearly with slag content. The stress–strain curve follows a logistic function in the rising stage and a rational fractional equation in the descending stage.This study demonstrates that lime-activated blast furnace slag is a sustainable and effective alternative for stabilizing expansive soils while reducing dependence on cement.