Alkali activation of copper mine tailings and low-calcium flash-furnace copper smelter slag

This paper studies alkali activation of copper mine tailings (MT) and low-calcium flash-furnace copper smelter slag (SG), two major types of wastes from the mining industry. The effect of SG content, curing temperature, and curing time on the unconfined compressive strength (UCS) of the MT/SG-based geopolymer is investigated systematically. Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy are also used to investigate the microstructure and elemental and phase composition of the MT/SG-based geopolymer. The results show that the addition of SG significantly improves the UCS and microstructure of the geopolymer. The improvement is mainly attributed to the high solubility of silica in the SG and the fine particle size of the SG. The inclusion of SG also leads to decrease of the optimum curing temperature (i.e., the temperature at the highest UCS) because of its higher reactivity than MT. In addition, the MT/SG-based geopolymer sets fast and gains a major portion of its ultimate strength within only 7 days. Based on the results, it can be concluded that the MT/SG-based geopolymer is a promising sustainable construction material for civil engineering applications.