Effects of thermal cycles on physical and mechanical properties of fiber concrete as compared with non-fiber concrete

In the case of explosions and fires, the rocks undergo cycles of heating and cooling, that is, they are exposed to considerable heat first and then cooled after extinguishing the fire. The purpose of this paper is to study how the temperature in a heating-cooling cycle can affect the physical and mechanical properties of fiber concrete (FC). During the heating phase in a heating-cooling cycle, experiments were performed on samples that were initially exposed to temperatures of 300, 500 and 700 °C and then cooled gradually to ambient temperature. At the same time, a series of experiments were performed on samples that were not exposed to a heating-cooling cycle. For this purpose, non-fiber concrete (NFC), polypropylene fiber concrete (PFC) and glass fiber concrete (GFC) samples were fabricated. The effect of the heating-cooling process on effective porosity, longitudinal waves velocity, uniaxial compressive strength, and tensile strength of PFC and GFC samples were investigated and compared with the NFC samples. The results show that fiber concrete containing 0.5% glass fiber has the highest tensile and compressive strength at 300 ° C. Fiber concrete containing 0.5% polypropylene fiber at 500 ° C has the highest compressive strength and at 700 ° C has the highest tensile strength among all types of non-fiber and fiber concrete with different percentages of fibers.