Physico-chemical and micro-structural behavior of cemented mine backfill: Effect of pH in dam tailings

The tailings created during ore processing have been a serious problem for mining companies and environment since it is a challenging task to effectively manage these highly voluminous/dangerous tailings. Therefore, several tailings disposal methods like tailings dams are needed for sustainable mining operations. The tailings accumulated in the dams reflect a critical raw material source since they might contain key base/precious metals, such as Au, Ag, Co, Ni, Cu and Zn. This study deals with the use-ability of dam tailings in cemented mine/paste backfill (CMB/CPB), considering the physico-chemical and micro-structural aspects. The backfill mixtures were manufactured at 76 wt% solid and 5 wt% cement contents, exposed to cure for up to 56 days, and tested for determining their strength (UCS), geo-chemical (i.e., pH, redox potential, and conductivity) and microstructure (i.e., XRD, TGA, and SEM) characteristics. Results disclosed that the strength of backfill was improved by the augmented basicity/age while only backfills made with sulfide-rich tailings had a noticeable drop in strength. This can be enlightened by the types of tailings (aged and fresh), and the hydration products shaped owing to the interaction of these tailings mixed with cement. While the values of pH detected by chemical tests were amplified up to 14 days, some decreased up to 56 days due to acid formations and erosions. This is the key function of CPB's deterioration physically, chemically, and microstructurally. Lastly, the outcomes of this study will allow us to further explore/assess the effects of dam tailings' potential usages on quality/performance of backfill mixtures.