Rheological properties of cemented paste backfill with nano-silica: Link to curing temperature

Current technical knowledge on the rheological behavior of cemented paste backfill (CPB) that contains nano-silica (nS) at different curing temperatures is insufficient. However, the assessment and an understanding of the yield stress and viscosity of CPB with nS added at the early ages are critical for using CPB technology in underground mines located in cold or warm regions and/or for deep mining. Therefore, the aim of this study is to investigate and develop a better understanding of the combined effects of temperature, addition of nS as an additive, and type of binder on the rheological properties of CPB. To this end, several CPB samples with different compositions are subjected to various temperatures (2 degrees C, 20 degrees C, and 35 degrees C) for up to 4 h. The yield stress and viscosity of the CPB samples are then measured at different time intervals of 0 min, 15 min, 1 h, 2 h, and 4 h. Moreover, electrical conductivity (EC) monitoring, and microstructural analyses (TG/DTG and XRD) are conducted on the samples. It is found that the yield stress and viscosity of the samples cured at 35 degrees C are much higher than the other samples. The enhancement of the rheological properties of CPB due to the coupled impacts of nS as an additive and higher temperature leads to reduced flowability of the paste. However, it is also found that the addition of a superplasticizer can partially compensate for the fluidity. Also, an increase in the water content reduces the yield stress and viscosity. The findings presented in this paper will contribute to the development of nano-CPB technology and its effective application in the backfilling operations of underground mines.