Concretos de pós reativos com adições de óxido de grafeno (GO)

Abstract

Concrete is increasingly present in civil construction due to its versatility; changes in the quantity of its constituent materials - binder (cement), aggregates (sand and gravel), and water - result in a compound with specific characteristics (durability, weakness etc.) and distinct properties (mechanical strength, permeability etc.). The presence of additives, in turn, can modify the properties of concrete, facilitating its application and improving its workability. Compressive strength, modulus of elasticity, and moldability are some of the determining factors in the use of concrete. Some resist compressive stresses of more than one hundred MPa, being called special concretes. In this category is reactive powder concrete (RPC), which does not have coarse-grained materials, usually consisting of cement, sand, quartz powder, active silica, superplasticizer additive, and water. Research involving other concretes has also been developed, such as conventional concrete with additions of graphene oxide (GO), a nanomaterial derived from the synthesis of graphite with oxidants and strong acids. Results of the addition of GO in concrete reveal an increase of 48% in flexural strength and 57% in compression, as mentioned in the literature review. Based on this premise, this research investigated the influence of GO on the properties of RPC. After physical and microstructural characterization of the materials, RPC test specimens without and with the addition of GO (contents of 0.025% and 0.05% by weight) were produced and evaluated. The results showed that with the addition of 0.025% GO, there was an increase in compressive strength (1.52%) and flexural strength (11.80%); the addition of 0.05% GO also promoted an increase in compressive strength (19.14%) and flexion (7.93%). Through Analysis of Variance and Tukey’s Test, it was found that only the RPC with the addition of 0.05% GO obtained a statistically significant increase in compressive strength, at the age of 28 days. The same did not occur for the flexural strength results, with none of the additions. This is due to the nature of concrete, which, when subjected to tensile forces, presents greater separation of aggregates, an effect not contained even with the presence of GO. Thus, with the statistical analysis of the results, the positive influence of GO was proven, which provided a greater refinement in the microstructure of the concrete, a statement corroborated by scanning electron microscopy tests. Also, the beneficial effect of the presence of GO was evidenced in terms of reducing the porosity and permeability of the RPC.