REAÇÃO ÁLCALI-AGREGADO: Uma investigação da reação álcali-Sílica em barras de argamassa produzidas com agregados com quartzitos do município de São Tomé das Letras- MG

Abstract

The objective of this study is to investigate the alkali-silica reaction (RAS) in mortar bars produced with quartzite aggregates from São Thome das Letras-MG, using the accelerated method recommended by ABNT NBR 15577-4 2018 and the method alternative by particle packing The chemical analysis of the cement was performed at the Institute of Technological Research (IPT) in São Paulo. The petrographic examination was done at the Paulista State University (Unesp) The aggregate specific mass determination test and the accelerated mortar expansion test were performed in the laboratory of the University Center of Southern Minas Gerais-UNIS/MG, at the Cidade Universitária campus in Varginha - MG. For the production of the mortar bars it was used quartzite extraction tailings. Three traces of mortar were produced, named Trace 1, using CP III cement, Trace 2, using CP V cement, and Trace 3, using CPV cement and applying alternative methodology for aggregate particle packing Traces 1 and 2 lasted 28 days and Trace 3 lasted 56 days. Considering traits 1 and 2 by the accelerated method, the results challenged the hypothesis that the aggregate would be potentially reactive to the RAS, since, although petrographic analysis indicates in a potentially reactive aggregate, the classification resulted in a potentially harmless aggregate for Traits 1 and 2 ABNT NBR 15577 2018 still emphasizes the term potentially, this means that the likelihood that the aggregate is reactive has not been ruled out and also indirectly suggests that further assays be performed to confirm the RAS As such, the alternative particle packing Trait 3 resulted in an expansion of 0.196% at 56 days, thus being classified as potentially reactive grade RI In general, the results were satisfactory because the aggregate showed strong reactive potentiality, since the amount of quartz in the mineralogical composition reached 95% In addition. Trait 2 even though classified as potentially harmless within 28 days was able to days, was able to achieve greater expansions. Thus, by applying Trace 3, it was possible to confirm the reactive potentiality of the aggregate.