Grain Size Analysis of Quartz in Potentially Alkali-Reactive Aggregates for Concrete: A Comparison Between Image Analysis and Point-Counting
This article describes a new image analysis method for grain size analysis of quartz in potentially alkali-reactive aggregates for concrete. The accuracy and speed of this new method are compared against the accuracy and speed of the traditional point-counting method. Quantitative petrographic examination of potentially alkali-reactive aggregates, based on grain size analysis by point-counting method, has shown that a relationship does exist between the total grain boundary of quartz and expansion results from accelerated mortar bar testing (Wigum, BJ (1995): Examination of microstructural features of Norwegian cataclastic rocks and their use for predicting alkali-reactivity in concrete. Engineering Geology (40): 195–214; Wigum, BJ, Hagelia, P, Haugen, M, and Broekmans, MATM (2000): Alkali aggregate reactivity of Norwegian aggregates assessed by quantitative petrography. In: Bérubé, MA, Fournier, B, Durand, B (editors): Proceedings of the 11th International Conference on Alkali-Aggregate Reaction in Concrete, Québec: 533–542). In this article, the authors performed quantitative petrographic examination of potentially alkali-reactive aggregates, based on grain size analysis by image analysis, of a few selected samples. The results were compared against the results obtained by the traditional point-counting method for the same samples. This approach revealed that image analysis is more time efficient than point counting without compromising the accuracy of the results.
KeywordsAggregates for concrete ASR Image analysis Petrography
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The first author wishes to acknowledge financial support from Fundação para a Ciência e Tecnologia (FTC - Portugal) through doctoral grant SFRH/BD/41810/2007.
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