High-temperature mechanical properties and microscopic analysis of hybrid-fibre-reinforced high-performance concrete

Hybrid-fibre-reinforced high-performance concrete (HFHPC) and normal concrete (NC) are prepared and their high-temperature mechanical properties investigated. Compressive strength, splitting tensile strength, flexural strength and ignition loss are tested at room temperature and at 200, 400, 600 and 800°C. The microstructure of concrete specimens after heating at high temperatures is also observed using scanning electron microscopy. Results show that mechanical properties of concrete reinforced with hybrid fibre at room temperature and at high-temperature levels increased significantly. The compressive strength, splitting tensile strength and flexural strength of HFHPC are higher than those of NC at the given test temperatures, reaching their maximum levels after heating at 400°C. In excess of 400°C, however, the mechanical properties of HFHPC decrease as temperature increases, but still remain significantly higher than those of NC at the same temperatures. This phenomenon is most particularly observed in the splitting tensile strength. At 800°C, the compressive strength, splitting tensile strength and flexural strength of HFHPC are 1·24, 4·5 and 1·61 times that of NC, respectively.