14 - Leaching of concrete with mine tailings

Abstract

The utilization of mine tailings (MT) as feedstocks for the production of construction materials has been aggressively promoted by cement and concrete researchers in the last two decades. Besides being part of the concerted efforts to mitigate the negative environmental footprint of the construction industry, it’s also an opportunity to reduce the reoccurring loss of lives, health hazards, and environmental contamination typically associated with MT storage facility failures across the world. This paper summarizes key physical and chemical properties of some of the most widely investigated MTs, such as copper mine tailings (CMT), gold mine tailings (GMT), iron mine tailings (IMT), phosphate mine tailings (PMT), and tungsten mine tailings (TMT). The various standard leaching tests and the toxic metal leaching behavior of cement and alkali-activated matrices (AAM) incorporating these MTs were also reviewed. Outcomes from this review suggest that irrespective of the MT type and volume incorporated in cement and AAM, toxic metals were unfailingly well-solidified and stabilized, leading to insignificant metal leaching. However, while toxic metal releases were usually below regulatory limits, an upswing in the leachability of arsenic (As) and chromium (Cr) in composites containing high-volume MTs were also observed in some studies. This review also showed that carbonation and microcracking could negatively influence the leaching behavior of MT-blended composites. Thus it is proposed that the use of expansive agents, shrinkage reducing admixtures, chemical stabilizers, and microfibers as mitigation measures for crack-prone MT-blended composites need to be investigated in future studies.