Reuse Potentials of Copper Mine Tailings in Mortar and Concrete Composites

Abstract

The disposal of copper mine tailings (CMT) in finite containment facilities near mine sites is a serious human safety and environmental management challenge in most copper-producing countries of the world. Therefore, this study evaluates the reuse potential of the CMT as a 0%–30% partial substitute material for cement in paste, mortar, and concrete mixtures. The CMT was characterized first, and thereafter its effects on the performance of cement paste and mortar were evaluated via normal consistency, setting time, strength activity index (SAI), X-ray diffraction (XRD), scanning electron microscopy analysis, and autoclave expansion tests. Mechanical strength evolution of CMT-blended concrete mixtures exposed to water-curing and a sulfate-rich environment was also monitored for about a year. Cement paste and mortar test results indicate that while the CMT led to a slight increase in water demand and set retardation, all the CMT-modified mortar mixtures met the minimum SAI requirement of 75% at the 28th and 90th days. Moreover, free lime induced longitudinal expansion generally decreased with increasing content of the CMT in pastes. These improved performances engendered by the CMT were also replicated in concrete. Whereas only the mechanical strengths of concrete incorporating 5%–20% CMT were higher than that of the plain reference concrete, the sulfate resistance of all the CMT-blended mixtures was superior to that of the reference concrete. XRD results also confirmed that the potentials of the CMT as a cement replacement material is high. All in all, the environmental and material sustainability benefits arising from the use of the CMT in cement composites are enormous.