The Efficiency of Non-Destructive Testing to Estimate the Damage Level of Fiber-Reinforced Concrete Exposed to High Temperatures

The feasibility of determining the extent of damage in fibered concrete after being subjected to high temperatures, using non-destructive methods was investigated. The study was conducted on four concrete mixtures with different fiber types. The specimens underwent a curing process at 23 °C before being exposed to different high temperatures of 400 °C, 600 °C, and 800 °C. After cooling to ambient temperature, various non-destructive tests including ultrasonic pulse velocity testing (UPV), the resonance frequency test (RF), the dynamic modulus of elasticity (Ed), the thermal conductivity test (λ), and Schmid Rebound Hammer (SRH), were performed. To evaluate the sensitivity of non-destructive techniques to assess the damage of fiber-reinforced concrete, the Lemaitre coefficient was used as a variable to describe the extent of the damage. The results indicated that the highest damage levels were obtained through the modulus of elasticity technique regardless of the type of concrete mixture or temperature exposure. There was also a potential agreement found between thermal and ultrasonic methods in evaluating the thermal degradation of concrete.