Effect of Mine Water Environment on Durability of Solid Backfilling Based on Carbonated Coal-Based Waste

The durability of solid backfilling based on carbonated coal-based waste (CCBW) under mine water environments is critical for its engineering feasibility. This study investigates the deterioration mechanisms of CCBW exposed to acid solution (Acid W), alkaline solution (Alkaline W), and mine water (Mine W) through hydrochemical analysis, XRD, and SEM. Results reveal that the uniaxial compressive strength of CCBW decreased by 10.05, 3.93, and 1.62% after 28 days of immersion in the groups, respectively. Acid conditions induced CaCO₃ dissolution and gypsum formation, while alkaline environments triggered alkali–silica reaction expansion. Mine water exhibited minimal impact due to suspended particles mitigating ion exchange. Carbonation also enhanced the durability of CCBW by forming dense CaCO₃ clusters and C-A-S-H gels, thus reducing ion leaching. Notably, the average erosion resistance of carbonated samples (CCBW-5, 10, 30) was 2.32% higher than that of noncarbonated counterparts. These findings confirm the feasibility of CCBW applications in weakly alkaline mine water and highlight its potential for sustainable coal mining practices, aligning with carbon capture and circular economy principles.