Effect of nanosilica on the axial tensile strength of SFRC at high temperature

An independently designed heat-resistant clamping device was used in an axial tension experiment at high temperature to test three materials: normal concrete (NC), steel fibre reinforced concrete (SFRC) and SFRC with nanosilica (NSFC). The materials were heated to different temperatures in a high-temperature electric resistance furnace. The results showed that, up to 400°C, the axial tensile strength of NSFC, SFRC and NC improved as the temperature increased, reaching a maximum value at 400°C. Thereafter, a rapid drop in axial tensile strength was observed as temperature was increased further. Within the test temperature range, the tensile stress–strain curve of NSFC demonstrated a similar tendency as that for the SFRC, but NSFC generally withstood higher loads than SFRC. At room temperature, the axial tensile strength of NSFC was the highest at 2·66 MPa, which was 4·29 times that of NC and 52·9% higher than that of SFRC. The peak stress of NFSC was approximately 1·8 times that of SFRC. At 400°C, the axial tensile strength of NSFC was 3·09 MPa, 9·2% higher than that of SFRC and 119·7% higher than that of NC. At the test temperature, the fracture energy of NSFC was the highest, followed by SFRC, with NC showing the minimum fracture energy.