Efeitos das elevadas temperaturas em concretos autoadensáveis com altos teores de resíduo da biomassa da cana-de-açúcar e metacaulim

Abstract

The fines added to the self-compacting concrete (SCC) as an alternative to lower the high content of cement contribute to make the SCC a sustainable composite in order to minimize the production of CO2 by the cement industry. Furthermore, mineral additions can provide improvements in the mechanical properties and durability of the concrete. One of the parameters of durability is the behavior of the material in extreme situations such as when subjected to high temperatures, similar to those reached in a fire. In this situation, the decrease of the resistance and modulus of elasticity, changes in color and porosity, besides the spalling effect, can occur in the concrete due to the loss of water and microstructural changes. In this context, the present study aims to evaluate the behavior at high temperatures of self-compacting concrete with high levels of residues sugarcane biomass (SBA) and metakaolin (MK). For this, cement was substituted for 30% to 50% by mineral additions. In the fresh state, the properties were evaluated proving the workability of the concretes made. In the hardened state, the samples were evaluated at room temperature, 200 °C, 400 °C, 600 °C and 800 °C and analyzed by visual and tactile inspection, mass loss, compressive strength, ultrasonic pulse velocity, absorption by immersion, void index, specific mass, absorption by capillarity and X-ray diffraction. The results showed that SCCs with up to 40% of mineral additions are less sensitive to high temperatures and that higher metakolin insertion makes them more sensitive to high temperatures. Moreover, phase changes are visualized and the high content of mineral additions consumes Ca(OH)2 from the medium, forming gismondine and margarite.