Estudo do efeito pozolânico da cerâmica vermelha nas propriedades de concretos submetidos a temperaturas elevadas

Abstract

Concern about the environment and the scarcity of natural resources is currently growing. The civil construction industry is one of the industries that generates the most environmental impacts due to the consumption of resources, waste generation and emission of polluting gases. The Portland cement industry is responsible for extracting large amounts of clay and limestone and for the high rate of emission of carbon dioxide into the atmosphere. Another relevant problem in the industry is the inadequate disposal of waste, including red ceramic waste. One of the advantages of concrete, compared to other structural materials, is its resistance to high temperatures. Knowledge about the behavior of concrete with the use of red ceramic as pozzolan is already widespread. However, the behavior of this material when exposed to high temperatures has not yet been explored. Within this context, the objective of this research is to evaluate the influence of the use of red ceramic as a pozzolan in partial replacement of Portland cement, at levels of 10% and 25%, on the physical and mechanical behavior of concrete, at room temperature and after exposure to 200°C, 400°C and 600°C. For this purpose, specific mass, absorption, void ratio, ultrasonic pulse velocity, compressive strength, elastic modulus, weight loss, thermodifferential and thermogravimetric analysis (TDA/TGA) and visual analysis were carried out. The results of specific mass and modulus of elasticity did not show significant differences between the mixtures for all temperatures studied. As for the void ratio and absorption, the mixtures T10 and T25 showed the lowest values for room temperature and T10 the lowest value for 200°C. As for the temperatures of 400°C and 600°C, there was no difference between the mixtures. Mixture T10 showed lower weight losses, considering the three temperatures, and higher compressive strength for temperatures of 400°C and 600°C. The results showed that the partial replacement of cement by red ceramic is technically feasible for concrete exposed to high temperatures. In general, the replacement content of 10% is the most appropriate. In this way, the use of red ceramic in concrete exposed to high temperatures constitutes a way to reduce inadequate waste deposition, exploitation of non-renewable resources and environmental impacts caused by the manufacture of Portland cement, improving concrete performance after heating.