In-situ cementation backfill of alkali-inspired ultrafine copper tailings: Performance and principles
Jirong Lan, Yuwei Xiang, Siyu Zhao, Yan Shao, Haobo Hou
Abstract
Ultrafine copper tailings (UTCT) are a type of bulk solid waste containing heavy metals, discharged from copper refining industries. Large stockpiles of these tailings pose significant environmental risks and lead to the wastage of valuable mineral resources. To address this issue, this study has developed a backfill material (solidified ultrafine copper tailings, S-UTCT) for mine shaft rehabilitation. This material utilizes waste alkali exciters and UTCT as base components. The primary process involves thoroughly mixing the alkali exciter with UTCT, followed by injection into a mold or pit for curing. The optimized process parameters are as follows: UTCT solid content of 50 wt%–60 wt%, mixing duration of 6–8 min, alkali activator dosage of 30 wt%–35 wt%, water-to-solid weight ratio of 0.2, mixing speed of 400 r/min, and curing period of 28 d. Mechanistic analysis revealed that the alkali activator induces mineral phase reconstruction and morphological reconfiguration of UTCT, driven by mechanochemical activation during ball milling. This results in improved compressive strength and effective immobilization of heavy metals. This paper presents a novel cement-free and burn-free method for preparing cementitious materials for recycling resources in mines.