Avaliação in situ da evolução do módulo elástico de concretos ligados com geopolímeros

Abstract

Refractory castables belong to the class of non-formed ceramic materials, which have the characteristic of being able to withstand high temperatures, without significant changes in their physical and chemical features. Although its high consumption is beneficial for the national economy, the manufacture of this material is accompanied by high energy costs and consumption of natural resources. In addition, the refractory disposal must also be done appropriately, as it may contain components that are dangerous for both the environment and humans. With that in mind, there is a growing interest in the production and use of alternative binders to calcium aluminate cements (CAC) with the aim of resulting in less environmental impact and still obtaining adequate performance of these ceramics under the conditions of use to which they are exposed. Among the available options, geopolymers have stood out because they are obtained from the alkaline activation of compounds rich in silica and alumina (such as natural materials or industrial byproducts/ waste) and constitute a binder with low environmental impact. In this context, this work aimed to evaluate and compare the elastic modulus of refractory castables bonded with CAC and/or geopolymers using the impulse excitation technique and in the temperature range of 30 to 1100C. The method used consists of a non-destructive test, which allowed monitoring the evolution of the elastic modulus of the samples along a heating and cooling curve of the specimens. Complementary tests, such as flowability, mechanical strength, porosity and density, were also carried out in order to complement the understanding of the behavior of the formulated refractories. The results indicated that, the castables bonded with geopolymer or with CAC + geopolymer present elastic moduli at least 50% lower than the mixtures bonded only with CAC. In addition, it was also observed that the porosity of geopolymer-bonded castables was considerably higher, due to the greater amount of liquid required in the processing of these compositions to obtain mixtures with equivalent rheological behavior (vibratable flow).