Super-sulfated cement incorporating gold tailings with lithium slag modification: Hydration behavior and heavy metal immobilization.

Abstract

The incorporation of industrial solid wastes such as gold tailings into cementitious systems represents a viable strategy to mitigate ecological footprints and advance sustainable resource management. However, the low reactivity of gold tailings and the associated heavy metals may hinder hydration and compromise the mechanical and environmental performance of such systems. In this study, a super-sulfated cement (SSC) system incorporating gold tailings was developed and modified with lithium slag. The hydration behavior, strength development, pore structure evolution, and heavy metal immobilization performance were systematically investigated through multi-scale characterization. The results showed that the incorporation of 20 % gold tailings led to a notable reduction in compressive strength (up to 34.83 % at 7 days) due to the presence of inert minerals and hydration inhibitors. However, the replacement of 10 % gold tailings with lithium slag significantly enhanced strength at all ages, refined the pore structure, and increased the formation of C-S-H and ettringite (AFt). Thermogravimetric and calorimetric analyses confirmed that lithium slag accelerated hydration and increased the content of chemically bound water. SEM-EDS analysis revealed that heavy metals including As, V, and Mn were effectively immobilized within AFt and C-S-H matrices. These findings provide mechanistic insight into the role of lithium slag in promoting hydration and stabilizing heavy metals in SSC systems containing gold tailings. The proposed binder system demonstrates high potential for large-scale applications in low-carbon construction materials.