Ultrasonic pulse velocity to assess the fire damage of concrete

During a fire, concrete structures behave in most cases very well. Therefore, it could be of economic interest to repair the damaged structure, as costs for demolition and rebuilding can be avoided and the building can be reused faster. The extent of damage can be assessed with a visual inspection, aided by non destructive techniques. This paper describes ultrasonic pulse velocity as such a method to assess the fire damage. Differences in velocity are expected as function of temperature, since cracks will occur in the cement matrix and in the interfacial transition zone due to thermal incompatibilities of the concrete constituents. Also, an increase of the porosity can be found, because of depletion of the hydration products. Furthermore, due to decrease of flexural and shear strength, structural cracks will occur. UPV can be used as a non destructive technique to assess the fire damage near the concrete surface