Carbonate-activated binder modified by supplementary materials for mine backfill and the associated heavy metals immobilization effects

Cemented paste backfill (CPB) is considered as one of the effective methods for resource utilization of tailings, while the high cost of ordinary Portland cement (OPC) limits its utilization. Considering the poor performance of Na₂CO₃-activated binders, in this work, supplementary materials including CaO, MgO, and calcined layered double hydroxide (CLDH) were used to modify their properties with the aim of finding an alternative binder to OPC. Isothermal calorimetric, X-Ray Diffraction (XRD) and thermogravimetry (TG) analysis were conducted to explore the reaction kinetics and phase assembles of the binder. Properties of CPB samples such as flowability, strength development and heavy metals immobilization effects were then investigated. The results showed that coupling utilization of MgO and CLDH showed better performance. The strength of sample Mg2-CLDH3 was about 2.94 MPa after curing for 56 days, which was higher than OPC-based sample. Besides, the cost of modified Na₂CO₃-activated binder was lower than OPC-based binder. Additionally, supplementary materials modified sample showed satisfactory heavy metals immobilization effects.