Value-added utilization of pre-wetted sulfur-rich tailings in calcium aluminate cement: mitigating shrinkage and refining microstructure

Sulfur-rich tailings (SRT), a byproduct of mineral processing, pose severe environmental risks while representing an underutilized resource. Conventional utilization in cementitious materials is hindered by the low reactivity of SRT, sulfur-induced volume instability, and adverse effects on workability. To address these challenges and explore a sustainable pathway for valorizing SRT in high-performance cementitious systems, this study proposes a pre-wetting treatment to facilitate the incorporation of SRT into calcium aluminate cement (CAC) for developing low-carbon cementitious materials. Experimental data demonstrate that the pre-wetting treatment extends both initial and final setting times by a maximum of 47.5% and 39.1%, respectively, relative to the reference mixture. This process concurrently enhances workability and promotes the hydration reaction, evidenced by a 4.3% to 14.3% increase in chemical shrinkage measured at 7 days. With 18% SRT incorporation, the pre-wetted samples exhibit a significant reduction in 28-day shrinkage, with autogenous and drying shrinkage decreasing by 44.2% and 31.9%. Furthermore, this modification contributes to a refined microstructure and improved mechanical strength. This work provides a practical approach to valorize SRT, effectively mitigating the performance limitations of CAC and advancing sustainable cementitious material development.