Avaliação da resistência residual de lajes alveolares em concreto armado em uma edificação industrial após incêndio

Abstract

Concrete, during exposure to elevated temperatures, is characterized by low thermal diffusivity and incom-bustibility, resulting a satisfactory performance against fire. However, chemical and physical changes occur in its components. The stability of the compound relates to its microstructure, so it is possible to verify the material degradation using advanced techniques of microstructural analyses. In this context, the use of mate- rials tests, such as diffraction and fluorescence X-ray, proves attractive. In this paper, it is described the prefabricated cellular slab inspection, an industrial building, which has undergone exposure to high temperatures emanating from a fire in the building ground. It was evaluated the structural element by chemical characterization tests with different thickness of the concrete slab, estimating the temperature reached in each layer and, consequently, the resistance loss of the structural element. From the results, it was found the temperature of approximately 700 ºC in the slab surface and less than 100 °C in the deeper layers. It was estimated the reduction in strength of concrete in the order of 25 % in 20 mm layer and negligible reduction in the region of prestressed wire, attesting to the structural safety of the structure after the accident.