Spalling behavior of high-strength polypropylene fiber-reinforced concrete subjected to elevated temperature

This study aims to investigative the relationship between the pore pressure and the explosive spalling of polypropylene (PP) fiber reinforced concrete when subjected to high temperature. Using the vapor pressure gauge, the moisture measuring sensor, and the thermocouple to measure the vapor pressure, moisture content, temperature, and the temperature on the heated surface of slab specimen, and observing the explosive spalling for the specimens of cylinder and slab made of PP fiber concrete. Test results showed that only the cylindrical specimen without PP fiber and 100% moisture content was apparently subjected to explosive spalling. Comparing with the test results of the slab specimen, the moisture content of the cylinder specimen had a significant effect on the occurring of explosive spalling. On the other hand, the effect of PP fiber on explosive spalling was obviously improved. The control slab specimen without fiber presented explosive spalling on the fire-exposed surface, causing the steel bar to be exposed to air, while the internal temperature rose faster than the PP fiber slab specimen without explosive spalling. The non- PP fiber slab specimen is affected by explosive spalling, the heat trend effect of temperature showed more obvious, and its moisture movement was more rapid than the slab specimen with PP fiber. Under similar moisture content, the slab specimen without PP fiber started sooner to explosive spalling with a serious explosive failure, on the contrary, the slab specimen with 0.1% PP fiber was completely without explosive spalling, indicating the significant effect of anti-explosive spalling by adding PP fiber in concrete.