Strength and deformation behavior of cemented foam backfill in sub-zero environment

Abstract Mining operations in permafrost or cold region have an urgent need to understand the behavior of frozen cemented foam backfill for its practical application. The aim of this paper is to experimentally investigate the strength and deformation behavior of frozen cemented foam backfill (FCFB) that contains cementitious material, foaming agent and aggregates with different particle size distributions in sub-zero environment (−10 °C). Several techniques have been used to examine the mechanical properties and the microstructure. The experimental results show that the strength and elastic modulus of FCFB increases as the ultra-fine particles content of building stone waste in FCFB increases. With the extended freezing time, FCFB exhibits more ductility due to strain-hardening. The mechanical strength of FCFB has a slighter increment with increased freezing interval time. Freeze-thaw cycles lower mechanical strength by deteriorating the structure. Additionally, FCFB with a higher content of ultra-fine portion presents a higher degree of cement hydration because of more contained unfrozen water, and the significant reduction of hydration rate occurs at an early age due to large amount of water freezing into ice. These findings will provide technical information for the optimal design of cemented foam backfill in cold-region.