Avaliação da interação de mecanismos expansivos em concreto produzido com areia de minério de ferro

Abstract

The durability of concrete structures is a topic of growing technical-scientific interest due to the frequent occurrence of pathological manifestations that compromise the integrity and service life of constructions. Among these manifestations, internal expansive reactions such as alkali-aggregate reaction (AAR) and delayed ettringite formation (DEF) stand out, which can also occur simultaneously. This study aims to evaluate the interaction of these expansive mechanisms in concretes produced with sand from iron ore extraction, a promising industrial by-product. The research was conducted through an experimental program that involved the physical and chemical characterization of iron ore sand, the production of high-strength concrete with 65% of this material relative to the total fine aggregate, and the induction of expansive reactions, both in isolation and combined. Dimensional variations over time were monitored, and non-destructive, physical, and mechanical tests were carried out, along with microstructural and chemical analyses to understand the effects of the reactions occurring both in isolation and simultaneously. The results indicated that, up to the age of 200 days, the combination of expansive mechanisms did not amplify the levels of concrete degradation. Furthermore, the alkali-aggregate reaction (AAR) showed a faster kinetics compared to delayed ettringite formation (DEF), and it was still predominant in concrete degradation when the mechanisms occurred combined.