REAÇÃO ÁLCALI-AGREGADO PELO MÉTODO ACELERADO EM PRISMAS DE CONCRETO: avaliação de agregados de quartzito provenientes do município de São Thomé das Letras-MG

Abstract

Engineering is in constant evolution, allowing us to study problems that were not possible before due to lack of technology. The most used material in civil construction is concrete and there are several pathologies that affect its durability and mechanical resistance. One of these pathologies is known as alkali-aggregate reaction (AAR); it is a chemical reaction that occurs inside the already hardened concrete, between cement and aggregate components when the structure is in contact with water. The AAR produces a gel that expands and generates tensile stresses inside the concrete causing cracks that reduce its mechanical strength. A study of reactive potentiality in concrete produced with the coarse quartzite aggregate from extraction tailings from the city of São Thomé das Letras, southern Minas Gerais, was performed. The study was based on the ABNT NBR 15577:2018 standard, which determines all parameters and requirements for the performance of AAR verification tests. The study contemplates the following steps: definition of materials for the production of concrete; determination of the physical indexes of materials; production of concrete and performance of measurements. In this step, a petrographic analysis was performed to verify the mineralogical composition of the quartzite and also the production of the concrete prisms by the accelerated method where the test duration is 20 weeks to verify the reactive potentiality. The results of the petrographic analysis carried out at Universidade Estadual Paulista (UNESP) - Rio Claro Campus and measures of the variation of the expansion of the concrete prisms are presented in the study content. The result of the analysis was satisfactory due to the initial reactive classification of the aggregate, however in relation to the prisms the tests have not yet been finalized, but it can already be stated that the aggregate reached a degree of reactivity potentiality as predicted in the petrographic analysis