Abstract
The alkali-aggregate reaction (AAR) in concrete structures is a problem that has concerned engineers and researchers for decades. This reaction occurs when silicates in the aggregates react with the alkalis, forming an expanded gel that can cause cracks in the concrete and reduce its lifespan. The aim of this study was to characterize three coarse granitic aggregates employed in concrete production in northeastern Brazil, correlating petrographic analysis with the kinetics of silica dissolution and the evolution of expansions in mortar bars, assisted by SEM/EDS, XRD, and EDX. The presence of grains showing recrystallization into individual microcrystalline quartz subgrains was associated with faster dissolution of silica and greater expansion in mortar bars. Aggregates showing substantial deformation, such as stretched grains of quartz with strong undulatory extinction, experienced slower dissolution, with reaction and expansion occurring over longer periods that could not be detected using accelerated tests with mortar bars.
Highlights
The alkali-aggregate reaction (AAR) is a phenomenon that has concerned civil engineers and researchers for decades
Given the uncertainties described above, this study investigated the influence of quartz morphology on the AAR, using three granitic aggregates that are widely employed in reinforced concrete structures in Sergipe State
2 28 results indicated that the aggregates had similar chemical compositions, textural evaluation using optical microscopy revealed significant differences, especially in the case of sample C
Summary
The alkali-aggregate reaction (AAR) is a phenomenon that has concerned civil engineers and researchers for decades This reaction has been studied since the early 1940s in order to understand its causes and develop ways to mitigate its effects. Due its complexity, it has attracted the attention of workers in fields as diverse as chemistry, physics, geology, and civil and materials engineering. In Brazil, an extremely large country, techniques used in some regions may not be practicable in others. The reasons for these differences include the use of aggregates from a variety of sources, cements with different chemical compositions, different pozzolans and chemical additives, and different environmental exposures
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