Different manifestations of the alkali-silica reaction in concrete according to the reaction kinetics of the reactive aggregate

The alkali-silica reaction (ASR) is caused by the presence of reactive aggregates in contact with sufficiently alkaline pore solution and a moisture level above 80%, which leads to the formation of expansive products that cause cracking and deterioration of the structures. Petrographic analysis of the ASR damaged microstructure provides information about the detection, analysis, and progress of the reaction. A stereobinocular and a polarizing optical microscope were used in order to observe and establish the relationship between ASR development in rapid or slow-reacting aggregates. The origin, mineralogical composition and fabrics of the constituent of the two types of aggregates were analyzed first. The progress of reaction was then studied on four concrete samples analyzing the different characteristics and textural patterns imprinted on the aggregates and the mortar. From the study it follows that the mineralogy and fabric of the rocks involved are responsible for different manifestations of the reaction in the aggregate and in the interfacial transition zone, causing damage that can diminish the strength and durability of concrete.