Effects of carbonaceous and ash synergism on the properties of coal mine solid waste filler materials: modulation of hydration mechanisms, strength generation mechanisms, and fine-scale damage

Solid waste backfill disposal has great advantages in ecological environmental protection and comprehensive utilization of waste in mining areas. The process of coal mining causes a series of ecological damage such as surface subsidence, soil and water pollution, and land occupation, and the use of coal backfill mining technology not only effectively enhances the utilization rate of solid waste, but also reduces the environmental problems in mining areas. To explore the influence factors of coal mine solid waste raw materials on the filling body, this paper prepared coal-based solid waste filler materials (CBWFMs) using coal gangue, coal tailings, and cement as raw materials. The ash content of coal tailings was used as a common evaluation index for the performance of coal-based solid waste, which effectively responded to the influence of the carbonaceous content level of the raw materials and the ash composition content on the performance of the filler materials. The hydration mechanism, mechanical properties, and microscopic damage process of the samples under different ash conditions were explored using the heat of hydration test, UCS test, and μCT in-situ loading test. The effect of synergistic interaction on the formation of hydration products was investigated by BPMA mineral composition analysis and SEM-EDS analysis. The synergistic effect of carbonaceous and ash was most effective in improving the properties of filler materials at an ash content of 63.1%. The study of the composition of coal tailings helps to realize the purpose of artificially adjusting the properties of mineral cementitious composites.