Synthesis of low-carbon ternary slag-based binder for cemented tailings backfill: Effect of slag and activator characteristics

Abstract

Alkali-sulphate activated slag, a ternary binder made of industrial by-products, has emerged as the most promising binding agent in cemented tailings backfill (CTB) owing to its superior performance, reduced carbon emissions, and cost-effectiveness. Nevertheless, there have been very few investigations examining the influence of the precursor and activator characteristics on the properties of CTB. This study seeks to explore the influence of drying temperature of flue gas desulfurization gypsum (FGDG), granulated blast furnace slag (slag) properties, and calcium carbide slag (CS) to FGDG (C/D) ratio on the strength development of CTB. The findings demonstrate that the FGDG dried at 65 °C consistently yields the highest strength of CTB. The C/D ratio substantially influences the strength and growth of CTB. The optimum C/D ratio tends to decrease as curing age increases. The C/D ratio that yields maximum strength is seen to be greater for slag with a lower basicity coefficient ((CaO + MgO) / (SiO₂ + Al₂O₃)). Moreover, the drying temperature of FGDG, the properties of slag, and the C/D ratio influence only the quantity, not the kind, of hydration products. The findings can facilitate the synthesis of slag-based binders with reduced carbon emissions and enhanced performance for CTB.