Effect of curing temperature on time-dependent shear behavior and properties of polypropylene fiber-reinforced cemented paste backfill

• Shear behaviors of early-age FR-CPB are curing temperature-dependent. • Warmer curing temperature weaken advanced-age strain-hardening behavior. • Shear properties evolve with curing temperature and curing time. • Predictive models for shear properties were proposed. Due to the wide existence of shear stress in the mine backfill materials, the shear behavior of polypropylene fiber reinforced cemented paste backfill (FR-CPB) plays a crucial role in the safe design of exposed backfill mass in underground mines. Moreover, warmer curing temperature induced by geothermal gradient influences the evolution of geomechanical behavior of FR-CPB with curing time. Therefore, this study was conducted to investigate the curing temperature (20 °C, 35 °C, and 45 °C) and time (7, 28, and 90 days) dependence of the shear behavior of FR-CPB. The results showed that warmer curing temperature enhances the strain-hardening and softening behavior at early ages, while the pre-peak strain hardening behavior of FR-CPB becomes unnoticeable at advanced ages. Moreover, 90-day shear stiffness, cohesion, dilation angle, and brittleness index of FR-CPB with a fiber length of 13 mm and a fiber content of 0.5 wt% respectively increase by approximately 68%, 62%, 63%, and 65% as curing temperature increases from 20 °C to 45 °C. However, the angle of internal friction is insensitive to the changes in curing temperature. Additionally, predictive models were proposed for the evaluation of the shear properties of FR-CPB. The findings from this study can contribute to the successful application of polypropylene fiber reinforcement technique and sustainable reuse of waste tailings in the underground mine backfill operation.