Combined use of silica fume and steel fibre to improve fracture properties of recycled aggregate concrete exposed to elevated temperature

Converting construction and demolition waste into aggregates for concrete is a promising technology, which can reduce environmental pollution and the consumption of raw materials. The purpose of this research is to investigate the combined effects of steel fibres and silica fume on the fracture behaviour of recycled aggregate concrete (RAC) exposed to elevated temperature. A total of 90 notched beams were prepared and tested under three-point bending, after heating under elevated temperatures of 200, 400, 600 and 800 degrees C. Comprehensive studies were conducted to investigate the temperature dependence of failure mode, flexural strength, fracture energy, cracking toughness and fracture toughness. The results show that the solo use of recycled aggregates in concrete has remarkable detrimental effects on its fracture resistance under elevated temperature. The incorporation of steel fibres significantly enhanced the fracture resistance of RAC subjected to elevated temperature. Moreover, the combination of steel fibres and silica fume can further improve the fire resistance of RAC under bending. The incorporation of silica fume nonlinearly increased the fracture properties of steel-fibre RAC exposed to high temperature and 4% silica fume was founded to be an optimal choice. This research provides insights for improving the fracture properties of RAC under elevated temperature.