Effects of copper mining wastewater on the performance of waste-based low-clinker cement mortars

Abstract

The presence of copper mining wastewater (CMw) in wet copper tailings (CTs) significant impediment to the reutilization of wet CTs in cementing material. This paper investigates the influence of CMw on the performance of waste-based low-clinker cement (Lcc) mortars, aiming to address the fundamental issues related to the application of wet CTs. In this regard, four Lcc mortars were prepared by using CMw to replace 0, 25 %, 50 % and 100 % of tap water. The influence of CMw on the setting time, hydration kinetics, hydration products, pore structure, compressive strength and microstructure of Lcc mortars were analyzed. Experimental results show that the addition of CMw prolonged the setting times and retarded the hydration process of Lcc paste due to the presence of acids and organic substances in CMw. Nevertheless, the presence of Ca2+, Na+, and Mg2+ in CMw can accelerate the dissolution of Lcc, contributing to the formation of expansive ettringite and hydrotalcite. As a result, Lcc mortars with CMw possessed denser pore structures. By using 50 % CMw, the compressive strengths of mortars can be increased by 3.5 % at 3d, 5.21 % at 7d, and 8.75 % 28d. The feasibility of adding CMw in Lcc mortars was verified, which would serve as the foundation for the preparing of Lcc-based materials with wet CTs.