Abstract

With the growing depth of underground mining, issues surrounding solid waste storage and the effective use of mine water have become pivotal to achieving sustainable mining practices. The complex ionic composition of mine water impacts the performance of traditional cemented tailings backfill (CTB) materials. Gold mine tailings, combined with cement, were repurposed as the cornerstone raw materials in this investigation. Solutions with identical target concentration gradients for Cl−, SO42−, and HCO3− were prepared separately using NaCl, Na2SO4, and NaHCO3, respectively, with each salt dosed to achieve the desired anion concentration. These solutions served as mixing water for preparing samples with tailings and cement. Strength, energy dissipation characteristics, and microstructure of CTB were investigated by single-axis compression test, XRD, and SEM-EDS analysis. Experimental results demonstrate that adding three reagents—NaCl, Na2SO4, and NaHCO3 (covering Cl−, SO42−, and HCO3− ions, respectively)—at appropriate concentrations enhances mechanical properties. At their optimum concentrations, these salts increased the compressive strength of CTB by approximately 30%, reaching ~4 MPa. However, further increases in salt concentration produced inconsistent strength responses, with bicarbonate-containing mixtures exhibiting the most pronounced strength reduction. These effects are primarily attributed to competition between the introduced anions and cement hydration reactions, which alters the pore structure and consequently the density and strength of the hardened matrix. Incorporating different ion-covering backfill at appropriate concentrations enhances mechanical strength. These findings provide new opportunities for CTB mix design and mine water utilization. However, as this study considered only single-ion systems, further investigation is needed to elucidate the combined effects of multiple ions present in actual mine water.

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