Abstract
Clinker-free cementitious materials are essential for both lowering the costs of cemented paste backfill (CPB) and ensuring that the heavy metal leaching meets relevant standards. This study investigated the influence of Pb(Ⅱ) and Cd(Ⅱ) on the hydration and mechanical properties of slag-based low-carbon binders, as well as the solidification/stabilization (S/S) efficiency of Pb(Ⅱ)- and Cd(Ⅱ)-containing tailings. The presence of Pb(Ⅱ) not only retarded the binder hydration but also decreased the compressive strength, while such negative effects were relatively little when adding Cd(Ⅱ); besides, the addition of calcined quarry dust (CQD) reduced these adverse impacts. X-ray diffractometry and thermogravimetric analysis showed that both Pb(Ⅱ) and Cd(Ⅱ) can influence the phase assembles, and hydrocerussite was detected in the composites containing Pb(II). Moreover, a horizontal semi-dynamic surface leaching test revealed that the main mechanism of Pb(Ⅱ) and Cd(Ⅱ) leaching is diffusion and adding CQD reduces their leachability and mean effective diffusion coefficient. The resulting solidified/stabilized tailings fulfilled the heavy metal leachability and mechanical strength requirements for CPB; this demonstrates that low-carbon binders can be effectively used for the sustainable treatment of Pb(Ⅱ)- and Cd(Ⅱ)-containing tailings, for CPB applications.
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