Mechanisms of in-situ remediation of soil with lead and sulfate contaminants using multiple binder strategies: experimental and numerical studies

Solidification/stabilization (S/S) is a versatile process used in contaminated soil remediation. The development of green binders and the associated immobilization mechanisms is imperative to the remediation research due to the aggravated carbon/energy footprints of the widely employed ordinary Portland cement (OPC). In this work, a pyrite ash disposal site, where the soil has high lead and sulfates contents, was selected for lab-scale tests and the following in-situ field trials. Traditional binders (OPC and cement III/B) and alternative binders (calcium aluminate cement, mayenite-blast furnace mix, and alkaline-activated blast furnace slag) were preliminarily applied using the high-performance S/S pelletization treatment (HPSS^©). Systematic mineralogical and microstructural characterization and pH-dependent leaching tests were applied to investigate the S/S effectiveness of different scenarios. Subsequently, simulations were developed to identify the minerals controlling the leaching behavior of stabilized pellets. Overall, the proposed methodology is a pertinent tool for extrapolating the contaminated soil HPSS^© to realistic conditions.