Validating the Use of Slag Binder with 91 Percent Blast Furnace Slag for Mine Backfilling

The use of ground granulated blast furnace slag (GGBFS) is environmentally sustainable and prevalent in the cement industry, but the original alkali-activated slag binder cannot be used for mine backfilling. Few reports have studied slag binders with high slag proportions (>90%) and low-cost activators (solid waste is used) that have higher performance than cement for backfilling. To increase the utilization of slag in the mining industry, this work presents a new slag binder (SB) comprised of 91% slag powder and 9% activator (3% clinker, 5% desulfurized gypsum, and 1% mirabilite). Its performance was evaluated by testing its strength, yield stress, and viscosity, which are three key properties for backfilling. We also investigated its microstructure using SEM, XRD and thermogravimetric analysis (TG/DTG). The results showed that the SB composites have a slightly lower early-age ( 28 d). Although the SB backfilling composites had a twofold higher yield stress and nearly the same viscosity as Portland cement, the pressure drop in a pipe was only slightly higher through friction factor modeling. The proposed SB may provide a sustainable binder for the mining industry with better performance and lower cost.