Effect of sodium chloride concentration and pre-curing time on the properties of cemented paste backfill in a sub-zero environment

Abstract

The effects of NaCl concentration and pre-curing time on the properties of frozen cemented paste backfills (FCPB) are investigated in this study. Calcium sulphoaluminate (CṠA) is used as a mineral accelerator to increase initial hydration rate, and fly ash (FA) and ground granulated blast-furnace slag (GGBS) are used as mineral additives to minimize CO2 emission and binder cost. The FCPB strength behavior, binder paste freezing point, and hydration evolution are investigated experimentally. The results show that an increase in NaCl concentration and pre-curing time leads to a significant decrease in the freezing point of the binder paste, and the addition of CṠA further enhances the effect; thus, a high degree of hydration of the binder is obtained. Further, under a freezing condition, the effect of an increase in NaCl concentration and pre-curing time on the FCPB strength development depends on curing time. Finally, the binder used herein (10% CṠA and 10% GGBS addition) exhibited the lowest CO2 and cost in 90 g/L NaCl solution, and hence, it is expected to have prospective applications in cold regions.