Strength Development and Environmental Assessment of Full Tailings Filling Materials with Various Water-to-Binder Ratios

Abstract

In order to build green mines, goaf is often filled, supported, and sealed with a high-water material to eliminate a series of environmental problems and safety hazards caused by goaf. In this study, ordinary Portland cement, sulphoaluminate cement, and alkali-activated cement were used as binders to prepare full-tailings high-water materials for filling, with various water-to-cement ratios. The compressive strength development of consolidated tungsten tailings specimens prepared with various curing binders was observed, and the influence of various water–cement ratios on the strength development was analyzed. The environmental impact of mine backfill materials was assessed according to the life cycle theory (LCA), and these mine backfill materials were prepared by using various binders. The results show that when the water-to-binder ratio is 3, the strength of alkali-activated cement can reach 3 MPa at 28 days; at that ratio, the microstructure of alkali-activated cement is more compact. Through LCA analysis, the environmental load of alkali-activated cement is shown to be significantly lower than that of either Portland cement or sulphoaluminate cement; the LCA results show that the primary energy consumption using alkali-activated cement is reduced from the Portland and sulphoaluminate cements by 1319.32 MJ and 945 kg, respectively. These unusual reduction percentages are achieved because the production of alkali-activated cement by LCA does not have any negative environmental impact—the production of alkali-activated cement, with its primary component being industrial byproduct slag, so that the use of alkali-activated cement in tailings’ consolidation has a positive environmental impact.