Clean production of sustainable backfill material from waste gold tailings and slag

Gold tailings (GT) and slag disposed of in the landfill affect the environment. This study investigated the green process for the utilization of non-radioactive gold tailings and granulated blast furnace slag (GBFS) to synthesize a green and sustainable backfill material. The following mix design ratios of GBFS:GT were investigated; 100, 10:90, 20:80,30:70, 40:60, 50:50. Maximum dry density, optimum moisture content, and strength were studied. The elemental composition, mineralogy, micrography, and evolution of particle size distribution were studied for raw materials and developed stabilized specimens. The mix design containing 20% GBFS and 80% GT yielded the optimum strength of 0.9 MPa. Calcium magnesium carbonate and calcium sulfate dihydrate were some of the products formed. There was a significant change in the microstructure of the GBFS blended GT with the increment in GBFS content. From the evolution of the volume distribution, the generation of finer particles was evident with the stabilization of GT. There was a significant modal size change with the mix designs investigated. Particle size distribution (PSD) proved to have an impact on the strength development of GBFS modified GT. The specimen developed met the requirement for backfill bearing material, for the strength of 0.3–0.7 MPa for conventional engineering design and the strength below 1 MPa for freestanding backfilling material. The evaluation of stabilized material for environmental impact showed that the concentrations of the contaminants were within the stipulated standards. This study proved that readily available wastes were beneficiated to produce value-added construction material and solve environmental pollution challenges.