Evaluation of residual fire endurance of concrete slabs after fire exposure

Abstract

One of the important factors that must be considered in evaluating the integrity of structures for further use after exposure to fire is whether the fire endurance of specific structural elements or a structural assembly has been reduced to a value less than that required by the building code. While a building may appear to remain structurally sound after a fire, its structural members' fire endurance may have been impaired to the extent that occupancy cannot be permitted. Re-usability of concrete structures after fire is of economic concern to the owner, especially when there is no visible damage to the structural members. The objective of this research is to conduct a small-scale pilot study and use statistical analysis to investigate the possible cause-and-effect relationships of three factors on the residual fire endurance: exposure severity, recovery conditioning method, and recovery conditioning time lapse. This research provides information for predicting fire endurance loss of concrete slabs after exposure to fire and, as a consequence, for making decisions on the re-usability of the structure. The research results indicate that once the concrete slabs (102 mm thick, no reinforcement and no load) are exposed to a standard fire for more than 30 min their fire endurance will decrease by at least 20%.