Abstract: In order to study the effect of polypropylene fiber on the tensile strength of C80 high performance concrete (HPC) after high temperature, the high temperature test was carried out on C80HPC containing 0, 0.1% and 0.2% polypropylene fiber, and the cracking of concrete was observed and recorded. After the tensile strength test was carried out, the infrared temperature rise of the cross section of the C80 HPC was detected by infrared thermal imager. The relationship between the tensile strength of the HPC, the infrared temperature rise and the temperature of the fire was analyzed. The results show that the incorporation of 0.1% polypropylene fiber in C80 HPC can inhibit the occurrence of bursting; the tensile strength of HPC decreases with the increase of fire temperature, and the incorporation of polypropylene fiber will reduce the tensile strength of HPC. The established regression equation of fire temperature and infrared average temperature rise and tensile strength can be used to identify the fire temperature, residual strength and post-building recovery of HPC after fire.

Key words: polypropylene fiber, high performance concrete; fire temperature, tensile strength, infrared temperature rise