Physical and mechanical characterization of concrete exposed to elevated temperatures by using ultrasonic pulse velocity.

Experimental investigations were carried out for assessing the influence of thermal loadings on the physical and mechanical properties of plain concrete after fire exposure. Cylindrical specimens were subjected to thermal loading at different temperatures inside a muffle furnace; while cubic specimens were exposed to direct flame following the ISO 834 standard curve. For both specimens' geometries the thermal loading was applied until it reached the selected temperature which was held for an hour. The specimens were tested for weight loss, optical microscopy, ultrasonic pulse velocity, residual compressive strength, X-ray diffraction and porosity. It has been observed that with the increase in the thermal loading, the physical and mechanical properties experienced significant detriment. The results suggested that the ultrasonic pulse velocity method is appropriate as an indicator of concrete compressive strength and microstructural properties after fire exposure. [ABSTRACT FROM AUTHOR]