Reação álcali-agregado: investigação do comportamento de agregados da região sudoeste do rio grande do sul frente a utilização de diferentes tipos de cimentos portland

Abstract

The Alkali-Aggregate reaction (AAR) is a chemical reaction between Portland cement alkalis and certain (reactive) minerals present in the aggregates. When there is presence of water or moisture, the result of this combination is a gel with expansive characteristics, which fills the pores of the concrete generating an increase of internal tensions, resulting in cracking of the concrete and consequently loss of its mechanical properties and durability. This research evaluated the reactivity of three aggregates (three naturals sand and six rocks) used in a commercial scale in the South-West region of Rio Grande do Sul, in comparison with the use of different types of Portland cement (CPII-Z, CPIV and CPV ARI). The results showed that for aggregate mixing with the CP V ARI cement, only the aggregates, reference and the limestone of the city of Bagé were characterized as potentially innocuous, for the mixture with the CP II-Z cement, the samples of the aggregates of the cities of Alegrete, Quaraí and Uruguaiana were characterized as potentially reactive, the other aggregates combined with the same cement were characterized as potentially innocuous, due to being within the normative limits. Finally the mixture of the aggregates with the CP IV cement, shows that all the samples were characterized as potentially innocuous. It is concluded that the type of Portland cement chosen can significantly influence the reactivity of the selected aggregates, partially or totally mitigating the AAR.