Evaluation of the Effect of Exposure Duration and Fiber Content on the Mechanical Properties of Polypropylene Fiber-Reinforced UHPC Exposed to Sustained Elevated Temperature

This article presents the results of an experimental study conducted to assess the effect of sustained elevated temperature on the mechanical properties of ultrahigh performance concrete (UHPC). UHPC mixtures were prepared with four different dosages of polypropylene (PP) fibers, and each mixture was exposed to a sustained pre-spalling elevated temperature of 300 degrees C for five durations. The experimental data indicate that the used PP fibers were effective in providing sufficient strength and ductility to UHPC mixtures at room temperature. However, the PP fibers ceased to function as reinforcement in UHPC specimens that were exposed to the elevated temperature for 60 minutes. With an increase in the exposure period after melting of the fibers, the specimens exhibited a brittle mode of failure accompanied with an enhancement in the compressive strength and compressive modulus of toughness and a reduction in the modulus of elasticity and flexural strength. The significance of two variables (exposure duration and fiber content) was evaluated, and correlations between the mechanical properties and selected parameters were obtained by conducting a statistical analysis of the experimental data.