Reinforcement Effect of CaCl2 on Cementation Performance of Solid-Waste-Based Cementitious Materials for Fine Tailings

Cemented paste backfill with mine tailings provides a desirable solution for maximally utilizing mine tailings. Ordinary Portland cement (OPC) is the most widely used binder for cemented tailings backfills; however, the serious environmental problems resulting from OPC production and the drawbacks of OPC in cementing fine tailings motivate the investigation of novel binders characterized by environmental friendliness, cost-effectiveness, and efficiency. We previously synthesized solid-waste-based cementitious materials (SWCMs) for cementing fine tailings. In this study, CaCl₂ was added as an accelerator to further enhance the cementing performance of SWCMs for fine tailings. Adding a small amount of CaCl₂ accelerated the hydration of raw materials and prompted the formation of larger amounts of hydration products. As a result, the cementing performance of SWCMs for fine tailings was significantly enhanced through the combined effect of C-S-H gel and ettringite. The cemented fine tailings backfill can be hardened only after curing for ~36 h, with a 50% decrease in hardening duration compared to the control sample without CaCl₂. The optimal amount of CaCl₂ was controlled at 1.5 wt.%, and the sample strength reached 0.21 MPa at 36 h, even at a low binder-to-tailings ratio of 1:8, meeting the requirement of early strength of common cemented tailings backfills. The rapid hardening of cemented fine tailings backfills has significant implications for accelerating ore mining speed, improving mining production capacity, ensuring the safe environment of underground mining sites, and preventing the movement of surface masses in the terrain where mining production takes place.