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

摘要

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