Compression performance and microscopic mechanism of cemented high-sulfide tail fills under varying pH levels: The role of alkaline agents

Abstract

Sulfur-rich tailings are highly susceptible to acid generation during the filling process, which can adversely affect the pH and compressive properties of cementitious backfill. Hence, this study conducted an exploratory test to better investigate the changes in the compressive behavior and micro-mechanism of cementitious high sulfur tailings backfill material (CHSTB) under different pH conditions by adding alkaline substances. Samples were prepared using varying doses of fly ash (FA), sodium bicarbonate (SB), and calcium oxide (CaO) as alkaline agents. The strength and microscopic features of CHSTB were examined by UCS, pH, and SEM. Lab verdicts released that FA-coated CHSTB's strength outperformed the other materials, with the 3 % FA-doped CHSTB achieving the highest UCS of 1.34 MPa. In terms of pH, all CHSTBs were strongly alkaline (pH >= 10.8). However, the pH changes of CHSTB with FA and SB were minimal and dose-independent, while the addition of CaO significantly increased the pH (up to 12.5). SEM analysis revealed that CHSTB with 3 % FA and SB exhibited a denser microstructure. In conclusion, FA and SB proved to be more effective, with significant research and application potential. This study also provides the optimal concentration range for various alkaline agents, offering an important reference for enhancing CHSTB and improving filling technology.