Stabilization characteristics of copper mine tailings through its utilization as a partial substitute for cement in concrete: preliminary investigations

This paper presents the feasibility of incorporating copper mine tailings (MT) as a partial substitute for cement in the development of concrete. The copper mine tailings used for this study have been accumulating for several decades at the tailings dump of Hindustan Copper Ltd. at Khetri, Rajasthan. Hence, alternative uses of MT need to be thought while keeping in mind that the utilization should also take care of the mobility of the elements present in the tailings. Consequently, M25 grade of concrete was designed as per IS: 10262-2009 (Indian standard code of practice for guidelines for concrete mix proportioning, Bureau of Indian Standards, New Delhi), with 0-50 % substitution of cement with MT and water-binder ratio of 0.5. To determine the feasibility of the new design mixes, unconfined compressive strength (UCS) of the concrete mixes was studied. Also, the leaching behaviors of the heavy metals contained in the tailings solidified in the concrete were studied by semi-dynamic leaching test. The effectiveness of solidification/stabilization (S/S) treatment was evaluated by determining diffusion coefficients (De) and leachability index (L) calculated from the data achieved in semi-dynamic leaching test. It was observed that the UCS values decreased with the increase in MT content. However, at 10-15 % MT substitution, the concrete exhibited acceptable strength. The MT substituted concrete also appeared to be effective in immobilizing the leachable elements in the tailings to a considerable extent thus, stabilizing the waste. Overall, the study suggests that concrete with acceptable properties can be developed using moderate amounts of MT as a partial substitute for cement thus, suggesting an economic and sustainable use of the waste.