Fracture behaviors of a new steel fiber reinforced recycled aggregate concrete with crumb rubber

This paper investigated the fracture behaviors of a new Steel fiber reinforced Recycled Aggregate Concrete which consists of crumb Rubber (RSRAC). The effects of rubber content on the fracture behaviors of the RSRAC subjected to different temperatures were analyzed. In RSRAC, the steel fiber was used to improve the crack resistance of concrete, and the inclusion of crumb rubber is mainly for environment protection, energy dissipation and reducing the risk of explosive spalling during exposure to high temperatures. A series of concrete mixes were prepared with ordinary Portland cement, recycled coarse aggregates (RCA) or natural coarse aggregates (NCA), steel fiber with volume-ratio of 1% and crumb rubber with different replacement ratios of 0%, 4%, 8%, 12% and 16% for fine aggregate (sand). The fracture properties, including fracture toughness (KIC) and fracture energy (GF), of the different concrete mixes subjected to different temperatures (25 °C, 200 °C, 400 °C and 600 °C), were obtained through three-point bending tests on 72 notched beams with sizes of 100 mm × 100 mm × 515 mm. The results indicated that both the fracture toughness and fracture energy first increase and then decrease with increase of the rubber content; at certain rubber content, the mixes had the highest toughness. The thermal damage due to heating from 25 °C to 600 °C also obviously increased the fracture energy and critical crack mouth opening displacement (CMODcri), but it was not the case for the fracture toughness. It demonstrated that exposure to high temperature made all cementitious materials tested significantly more ductile and less resistant to crack propagation.