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 1100C. 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).
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