Ultrasonic Assessment of Damage in Concrete under Compressive and Thermal Loading Using Longitudinal and Transverse Waves

Concrete, when exposed to high temperatures, presents important changes in its properties of strength and deformation and, in extreme situations, these alterations can constitute risks to the integrity and the safety of the structures. This work presents extensive campaign with 70 cylindrical specimens and seven different mixture proportions: two of mortar and five of concrete, to analyze the propagation profile of longitudinal and transverse ultrasonic waves in concrete cylindrical specimens, associating the variation of the ultrasonic pulses with the level of compression stresses and the degree of damage imposed by high temperature. The compressive strength was within the range of 32 and 64 MPa and the specimens were exposed to temperatures of 250 degrees, 300 degrees and 350 degrees C. The results indicate that longitudinal and transverse ultrasonic waves can be successfully applied in the evaluation of diffuse damage cause by uniaxial compression load and exposure to high temperatures.