Experimental and modeling investigation of long-term leachability of nickel in re-molded cement-stabilized sediments

The environmental impact of recycling waste sediments as construction materials has raised significant concerns, particularly regarding the long-term leachability of heavy metals. This study investigates the leaching behavior of nickel (Ni) in cement-stabilized sediments through tank leaching tests and modeling approaches. Considering the practical construction scenario, the effects of curing age and ambient pH on Ni release were examined, including the impact of crushing and re-molding processes. The results indicate that Ni leaching follows a time-dependent pattern, strongly influenced by ambient pH but minimally affected by additional curing after re-molding. Across various curing ages, Ni release peaked between 9 and 16 days of leaching before gradually decreasing. Extreme acidic and alkaline conditions (pH = 1 and 14) significantly increased Ni leaching at later stages, whereas moderate pH conditions resulted in minimal mass loss. A leaching model based on non-equilibrium thermodynamics was developed, demonstrating good agreement with experimental data and reinforcing its reliability in predicting long-term metal release. These findings contribute to assessing the environmental feasibility of using cement-stabilized sediments in construction.