Behavior of Polypropylene Fiber-Reinforced Concrete Beams in Fire

This paper presents the results of an experimental study on the comparative response of polypropylene (PP) fiber-incorporated reinforced concrete (RC) beams under fire conditions. Five full-scale RC beam specimens, made with different batch mixtures comprising normal plain concrete (NPC) and fiber-reinforced concrete (FRC), were tested to assess their spalling performance and structural behavior under fire conditions. The main variables in the experiments were the amount and length of PP fibers. Deflections, temperatures, and spalling in the beams were monitored during fire exposure. FRC beams’ flexural failure occurs after 151 minutes at heating temperatures beyond 850°C, when deflections exceed span/20. When the concrete contains PP fibers (that is, FRC beams), the gamut of fire-induced spalling in RC beams gets reduced, increasing the fire resistance from 147 to 171 minutes (approximately 17%). Furthermore, test results show that adding 2 to 3 kg/m³ of PP fibers effectively releases the pore pressure through tensile cracking and reduces the amount of spalling in the FRC beams.