Reactive MgO-modified slag-based binders for cemented paste backfill and potential heavy-metal leaching behavior

As a binder to replace Portland cement completely for cemented paste backfill, the use of clinker-free binders combined with copper slag is proposed to achieve the purpose of low-cost mine backfilling and safe disposal of copper slag. We studied the influence of reactive MgO on the properties of cemented paste backfill (CPB) samples, including rheological characteristics, setting time, and compressive strength as well as the heavy-metal leaching behavior. The results indicated that the addition of reactive MgO increased the yield stress of the fresh CPB samples, leading to decreased flowability, whereas the compressive strength of the CPB samples was increased. Besides, the release amount of all the investigated heavy metals was decreased in the presence of reactive MgO due to the formation of additional hydrotalcite-like phases with the formation of a more compact structure. These results provide a strategy for the safe large-scale utilization of copper slag. (c) 2021 Elsevier Ltd. All rights reserved.