Effects of curing temperature on shear behaviour of cemented paste backfill-rock interface

Abstract

Understanding the shear behaviour of the interface between rock and cemented paste backfill (CPB) is critical for the cost-effective geotechnical design of underground CPB structures. Curing temperature is one of the key factors that can affect the shear behaviour and resistance of the CPB-rock interface. However, no studies have been performed to investigate its effects on the shear behaviour of the interface between rock and tailings backfill that is undergoing cementation. The main objective of this study is to therefore experimentally study the effects of three different curing temperatures (2 °C, 20 °C, and 35 °C) on the shear behaviour and strength of the CPB-rock interface. The obtained results show that higher curing temperatures (up to 35 °C in this study) can increase the rate of cement hydration and self-desiccation, thus increasing the peak shear stress at the interface between early age CPB and rock. However, the sample cured for a longer time of 28 days at a higher temperature of 35 °C has a lower shear strength than that cured at a lower temperature of 20 °C. This lower shear strength is due to the crossover effect, which is the phenomenon of temperature inversion in the strength of cementitious materials. The findings presented in this paper will contribute to a better assessment of the stability of backfill structures and a better design for them.