Influence of silica fume and low curing temperature on mechanical property of cemented paste backfill

Abstract

The cementing cost accounts for 75 percent of the total operations costs in a mine if cement is used as cemented material. Silica fume (SF), as potential cementitious material, can be used as a substitute of cement to fabricate cemented paste backfill (CPB). In this study, experimental studies were executed to investigate the mechanical properties and microstructure evolution of CPB incorporating SF and in an effort to assess the applicability of using SF as a partial cement replacement in cold region. The cement replacement level was set at 0% (control), 2.5%, 5.0% and 10.0% by the mass of cement. Furthermore, the effect of curing temperature (−1, 6, and 20 ℃) on mechanical and microstructural performance of CPB within 28 days was also studied. Results indicate that the optimal replacement level of 5.0% for CPB exhibit the highest compressive strength regardless of curing temperature and age. The low curing temperature retards hydration reaction, and the strength of CPB samples with silica fume cured at room temperature is higher than that cured at 6 ℃ and −1 ℃, however, the 28-day strength of CPB with 5% silica fume at low curing temperature (−1 ℃) is larger than that CPB without silica fume at room temperature. The strength incremental rate induced by replacement of silica fume at early age (e.g., 3 days) is more significant in comparison with that cured for 28 days. The microstructural results indicate that more hydration products (e.g. C-S-H, ettringite, and CH) are generated as silica fume dosage and curing temperature increases, thereby resulting in refinement of pore structure and improvement of CPB strength.