Application of the Sclerometric Method to Concrete Damage Assessment in Post-Fire Structures (IWCF RILEM 2025)

The article presents an analysis of the applicability of the sclerometric method for assessing the quality of concrete in structures after a fire, based on simple and quick experimental tests. The analysis is preceded by a presentation of important issues and problems that arise during the assessment of concrete structures after a fire. A total of 15 reinforced concrete members were tested, exposed to high temperature in a planned manner for 0 (reference members), 60, 120, 180, and 240 min. The members were made of three types of ordinary concrete differing in compressive strength (corresponding to classes C30/37 and C40/50) and aggregate (siliceous and basalt). Sclerometric measurements were carried out directly on the members’ heated surfaces and, after removing the external layers of concrete, on surfaces corresponding to the locations of the 350 °C and 500 °C isotherms. The relative rebound number, defined as the ratio of the average result on the tested surface to the average value on the unheated reference member surface, decreased significantly with the deterioration of concrete quality caused by fire temperature. The relationship between the relative rebound number and the standard relative decrease in compressive strength of heated concrete is also analyzed. Practical recommendations are presented on assessing the quality of the surface layer of concrete in structural members after a fire, based on readings of the relative rebound number.