Influence of the ultra-fine fly ash dosages on the mechanical properties of the sulfoaluminate cement-based high water backfill material at different curing conditions

To reduce the filling cost of the high water backfill material (HWBM) in mining backfill and improve the recycling utilization of the industrial waste such as the coal fly ash. The ultra-fine fly ash (UFA) was added to the HWBM as a partial replacement in this work. Therefore, a series of experiments were performed to investigate the effect of UFA on the mechanic properties of the HWBM at the different curing conditions, then the hydration mechanism of the HWBM blended with UFA was analyzed by XRD and SEM method. The result indicates that the strength of the HWBM decreased with the dosages of UFA increasing, but the addition of UFA can improve the strength decreasing of the initial HWBM decreased at the ages of 28 days. Additionally, the addition of UFA have no obvious effect on the hydration products under the standard curing condition, while the later mechanical properties increased as the dosages of UFA were less than 15 % at the ages of 28 days. It indicates that the addition of UFA can improve the weathering resistance of the HWBM with the curing time increasing effectively.