Análise do comportamento termomecânico em diferentes classes de concreto e com substituição de vermiculita

Abstract

Concrete is a widespread and used material worldwide, mainly due to its relatively low cost, the non-requirement of qualified labor to obtain it, in addition to its relative fire resistance. However, the behavior of this material, when subjected to certain conditions of loading and temperature, leads to microstructural changes that reflect on its macroscopic structure. Experimental studies have analyzed the damage caused by temperature increase considering the microstructural and macrostructural levels and, as the demand for concrete with a highly dense cementitious matrix and with a low void volume is increasing, there is an increase in the material's sensitivity to extreme thermal conditions, making it subject to microcracking, peeling and loss of load carrying capacity. It should also be noted that researches referring to the exposure of concrete elements to high temperatures lead to very inconsistent results and, therefore, new contributions on the subject are very important. In this context, there is a need to study the thermomechanical evaluation of concrete with light aggregates when compared with conventional concretes, that is, with stone aggregates commonly used in dosages. It is intended, in this work, to evaluate the thermomechanical behavior of concrete when it is exposed to high temperature gradients, considering that fires go up to 900ºC, and to understand the process of degradation of materials in these cases. The work consists of two stages, Stage I with the purpose of characterizing, studying and defining the materials and dosages for each type of concrete, in addition to the molding of test bodies to be evaluated and tested. In Step II, the tests of absorption, specific mass, axial compression strength, tensile strength by diametrical compression, static modulus of elasticity and ultrasonic pulse velocity were performed in each of the samples subjected to different temperatures (TA (room temperature); 200; 400 and 800°C). As a conclusion and according to the analysis of the results, it was found that, at room temperature, the use of vermiculite showed differences in porosity and specific mass of the material, however, with the increase of temperature gradients, these differences disappear, which can be explained by the increase in cracking, loss of mass and increase in pore structure. It was also observed that, for the test parameters, it can be concluded that high temperature has a direct influence both on conventional concretes and on concretes with substitution by vermiculite.