Synergistic effect of activator nature and curing temperature on time-dependent rheological behavior of cemented paste backfill containing alkali-activated slag

Cemented paste backfill (CPB) that contains alkali-activated slag (AAS) produces more desirable properties and performance (enhanced fluidity, higher strength, lower cost, and limited carbon emission) as compared with CPB made with cement. Significant efforts have been devoted to the study of the effect of the individual factor on the rheology of AAS-CPB. However, the synergistic effect of curing temperature, time, and activator nature is still unclear. Therefore, the current research aims to investigate the time-dependent rheology of AAS-CPB under the combined influence of curing temperature, silica modulus (Ms), and activator concentration (AC). The findings revealed that a higher curing temperature results in a reduction in fluidity and an increase in the thixotropy of CPB. The evolution of rheological parameters of AAS-CPB is more insensitive to the curing temperature as compared to that of OPC-CPB. During the initial 2 h, higher AC can weaken the rheological parameter. However, a more rapid growth rate of rheological properties was observed after 2 h. The rheological parameters of AAS- CPB with higher Ms are always lower than those of AAS-CPB with lower Ms at all temperatures studied. In addition, the discrepancy in the linear correlation between thixotropy and plastic viscosity for OPC-CPBs and AAS-CPBs indicates the different hydration rates of slag and Portland cement. These findings are beneficial in guiding the mix proportion design of AAS-CPB in mines with various underground temperatures.