Experimental behavior of ultra high performance fiber reinforced concrete beams under fire conditions

This paper presents results from an experimental study on the behavior of ultra high performance fiber reinforced concrete (UHPFRC) beams subjected to combined effects of structural loading and fire exposure. Five large-scale UHPFRC beams, fabricated with different batch mix proportions, were tested to evaluate the structural behavior and spalling performance under ambient and fire conditions. The test variables included the presence of polypropylene fibers, load level and fire exposure scenario. The test results show that UHPFRC beams are highly susceptible to explosive spalling in the compression zone (on the sides) of the beam section leading to lower fire resistance, as compared to conventional normal or high strength concrete beams. When polypropylene fibers are present in UHPFRC, the extent of fire induced spalling decreases, resulting in higher fire resistance. Results from fire resistance experiments indicate that higher load level aid in release of pore pressure through tensile cracking and decrease the extent of spalling in UHPFRC beams. In addition, UHPFRC beams with polypropylene fibers exhibit better performance under design fire scenarios with distinct cooling phase than under fire scenarios without a decay phase.