Mechanical Properties of HPC Incorporating Fly Ash and Ground Granulated Blast Furnace Slag After Exposure to High Temperatures

The behavior of concrete structures after being exposed to elevated temperatures is considered one of the great vital concerns in Civil Engineering. Moreover, as elevated temperature have adverse effects on the mechanical properties of concrete members, it’s important to find solutions to improve these properties at elevated temperature. This study aims to investigate the effect of supplementary cementitious materials (SCM) on the high performance concrete (HPC) compressive, tensile, and flexural strengths after exposure to different temperatures of 200 °C, 400 °C, 600 °C, and 800 °C. In preparing HPC, different parameters were considered including SCM type, fly ash (FA) or ground granulated blast furnace slag (GGBFS), adding 0.5% (by volume fraction) steel fiber (SF), polypropylene fiber (PP) and hybrid fibers. The results were compared with those for high strength concrete (HSC) and normal strength concrete (NSC). The results showed that using FA and GGBFS, SF, and hybrid fibers can significantly improve the residual mechanical properties of HPC, while using PP fiber has an adverse effect on the residual mechanical properties of HPC especially residual tensile and flexural strengths. The standard code curves underestimate the residual mechanical properties of HPC after 200 °C