Compressive and shear response of fibre-reinforced backfill: impact of field temperature

Fibre-reinforced cemented paste backfill (F-CPB; a mixture of tailings, fibre, cement, and water) is exposed to non-isothermal curing environments in the field. However, no investigations have been conducted on the impact of non-isothermal curing environments on F-CPB compressive strength, shear characteristics and stress–strain behaviour, although these are important design parameters for F-CPB structures. Therefore, a series of mechanical and microstructural tests were performed on samples with and without fibres exposed to isothermal and non-isothermal conditions. It was found that the non-isothermal curing condition substantially enhances the F-CPB compressive strength and strength gain ratio. The shear strength, cohesion and internal friction angle of the F-CPB samples cured under non-isothermal conditions were higher than those cured under isothermal conditions. These impacts of non-isothermal curing on the compressive and shear characteristics of F-CPBs are related to the temperature-induced change in the microstructure of these samples. The F-CPBs cured under non-isothermal conditions had more hydration products than those cured under isothermal conditions. Moreover, mercury instrusion porosimetry (MIP) tests showed that the F-CPBs subjected to non-isothermal conditions had a finer pore structure than those exposed to isothermal conditions, which contributed to an enhancement of the mechanical characteristics of the F-CPBs subjected to non-isothermal curing.