Flexural Performance of Polypropylene Fiber Reinforced Scoria Aggregate Concrete Beams after Exposure to Elevated Temperatures

Abstract

To study the residual strength of concrete beams made from a new type of scoria aggregate after being exposed to fire, six concrete beams were tested, including three normal aggregate concrete (NAC) beams and three scoria aggregate concrete (SAC) beams. First, the beams were exposed to fire for 60 min (2 beams) and 90 min (2 beams), and then subjected to four-point bending tests. The effect of the duration of fire exposure on the load-midspan deflection relationship and the beam failure modes was evaluated with an advanced digital image correlation (DIC) camera. The experimental results indicate that at certain locations, the temperature of the SAC beams after 60 min and 90 min of fire exposure was lower than that of the NAC beams. When the duration of fire exposure was 90 min, the ultimate load capacity of the SAC beams decreased by approximately 11% compared to the load capacity of the beams at ambient temperature, while the load capacity of the NAC beams decreased by approximately 17.5% under the same conditions. After a fire, the internal bonds of concrete are damaged, and this damage manifests as concrete spalling, compressive strain, gap spacing, and reinforcement damage after loading. In this study, a numerical model was also developed and the flexural response of the NAC and SAC beams under different fire times was simulated. The results of the numerical model showed a good agreement with the experimental results. Using the numerical model, the influence of several important parameters on the ultimate capacity of the SAC beams for different fire exposure times was studied.