Reuse of a contaminated soil stabilized by a low-carbon binder as roadway subgrade material and mechanical performance evaluation

This study evaluates the feasibility of utilizing a hydroxyapatite-based binder (termed as SPC) stabilized contaminated soil in a decommissioned electroplating industry site as roadway subgrade material, where SPC is a mixture of superphosphate (SP) and calcium oxide (CaO) powders in a proportion of 3:1 by dry weight basis. Traditional Portland cement (PC) was used as a control binder for comparison purpose. The leachability of the stabilized soil was evaluated at 28 d. The engineering properties including dry density, soil resistance, and dynamic deflection modulus, were investigated at 1 d, 7 d, 28 d, and 600 d after construction. The results showed that stabilization using SPC is effective for immobilizing target contaminants of nickel (Ni) and zinc (Zn) in the contaminated soil and improving its mechanical properties including dry density, soil resistance, and dynamic deflection modulus. The SPC binder exhibited superior performance to PC in term of higher immobilization effectiveness of Ni and Zn, shorter curing time, and lower carbon footprint. The SPC-stabilized soil showed inferior strength, stiffness, and water sensitivity to those of the PC-stabilized soil.