Time-dependent rheological and mechanical properties of silica fume modified cemented tailings backfill in low temperature environment

The objectives of this study are to examine the rheological and mechanical property of fresh CTB incorporating silica fume (SF) at low temperature and in an effort to assess the applicability of using SF as a partial cement replacement. The cement replacement level was set at 0% (control), 2.5%, 5.0% and 10.0% by weight. Furthermore, the effect of curing temperature (12, 1, 6, and 20 degrees C) on time-dependent rheological behavior of fresh CTB within 240 min was also examined and analyzed. The results indicate that the time-dependent rheological behavior of fresh CTB is significantly affected by curing age and silica fume replacement. Both the yield stress and viscosity increase steadily as curing time elapses, and the CTB sample cured of 20 degrees C has the highest yield stress and viscosity, while that cured of 1 degrees C presents the lowest values for all the curing periods. However, the CTB samples cured of 12 degrees C show a slight decrease in viscosity and yield stress until 40 min, then follow by an instant increase due to water frozen. In addition, the yield stress of fresh CTB is elevated by mixing of silica fume, but the viscosity decreases. The uniaxial compressive strength of CTB at low temperature (1 degrees C) is enhanced with increasing of silica fume, and the CTB samples with 5.0% silica fume replacement for cement exhibit the highest compressive strength among all CTB mixtures regardless of curing age. The CTB samples with 5% silica fume present refiner pore structure than that with 0% and 10.0% replacement.