Spalling Prevention of Ultrahigh-Performance Concrete: Comparative Effectiveness of Polyethylene Terephthalate and Polypropylene Fibers

This work explored the feasibility and effectiveness of using recycled polyethylene terephthalate (PET) fibers as an alternative to conventional polypropylene (PP) fibers in preventing the thermal spalling of ultrahigh-performance concrete (UHPC). The effect of PET fibers of varying dosages and geometries on the spalling behaviors of UHPC subject to various heating regimes was studied. The results showed that the PET incorporation into UHPC can effectively prevent the occurrence of heat-induced cracking and spalling. However, compared with PP fibers, a higher dosage of PET fibers was required to eliminate the spalling risk of UHPC. The relatively low mitigation efficiency of PET fibers compared with PP fibers may be attributed to its higher melting temperature, which retarded the formation of interconnected channels. Nevertheless, the incorporation of PET and PP fibers increased the permeability of UHPC even before the heat treatments and fiber melting, which contributed to a reduced spalling propensity of the UHPC.