Efeitos da alta temperatura na microestrutura do concreto

Abstract

Population densities have caused the verticalization of cities, demanding large-scale use of reinforced concrete in building structures. This phenomenon brings with it a combination of risks, including fire. Fires can affect the strength of concrete. Research has been carried out to study the behavior of concrete in a fire situation and its loss of resistance is already known. Understanding the behavior of the concrete microstructure and its influence on the residual resistance of structural elements can trigger solutions to increase this resistance in fire situations. The present study aims to seek knowledge about the influence of high temperatures on the microstructure of concrete, relating them to studies already carried out. It is also known that the intensity of fire in a fire situation does not occur in a standardized way and affects the concrete structure randomly, depending on the position of the element in the structure and as the temperature advances towards the interior of that element. In this study, this condition was not evaluated, but the microstructure in general. For the present study, conventional concrete test specimens were made with the addition of hematite iron oxide (Fe2O3), which can function as a colorimetric indicator of the temperature increase inside the element. The specimens were heated in a muffle furnace and after being subjected to the temperature, the microstructure of the elements was studied and compared between the groups in order to verify the changes that occurred due to the heat. The results obtained show that the microstructure of the concrete, in the area affected by high temperatures, suffers significant deterioration, chemically altering the components of the cement paste and creating microcracks in the aggregate-cement paste transition zone.