Potential alkali silica reactivity of various rock types in an aggregate granite quarry

Generally, alkali-silica reaction (ASR) is considered as an internal chemical reaction between the alkaline components in the cement and active silica-silicate based mineral constituents of some aggregates. The use of aggregates susceptible of ASR in concrete can cause a severe degradation of the concrete structures because of several reasons e.g. high humidity and sea saline water. Utilization of potentially alkali-silica reactive aggregates needs to conduct reliable tests for evaluating their alkali-silica reactivity. The objective of this study is to identify the potential alkali-silica reactivity of several aggregate rock types. To achieve this objective, a granite quarry which is operated to produce aggregates was selected and investigated. Six samples of five igneous rock types were collected from the mentioned site and an extensive laboratory tests consisting of petrographic examination and accelerated Bar Mortar test were conducted on these samples to assess the potential alkali-silica reactivity. According to ASTM C 1260 suggested method, three Bar Mortar tests were performed on each sample. Based on the obtained results, it was found that five samples of all six samples were considered as innocuous due to their average expansion rates which are less than 0.1%. Only one sample which was collected from the fault zone considered as reactive with average expansion rate of 0.2404% which is more than 0.2%.