Study on the modification effect and mechanism of tailings powder on coal gangue-based mining cementitious filling material

Based on the problems of high carbon emission and high cost of traditional mining methods and filling materials, the tailings powder modified Coal Gangue-based Cementitious Backfill Material (CGCBM) was used for paste filling mining. In this study, the samples were prepared with different tailings powder content and different curing ages. The compressive strength test, XRD, SEM test, and NMR test were used to explore the changes of macroscopic strength and microstructure of the material. The results show that adding 50% tailings powder has the most obvious optimization effect on the performance of CGCBM. Tailings powder particles fill the surface holes of the fine aggregate of coal gangue in the early cement hydration process, reduce the water absorption of the aggregate. In addition, the active substances such as Ca2SiO4 play the pozzolanic effect, stimulate the secondary hydration of slurry, make the microstructure closely, and thus improve the macroscopic mechanical strength.