Department of Mineralogy, Petrology and Geochemistry, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic, e-mail: mirka@sci.muni.cz

Department of Geotechnics, Faculty of Civil Engineering, Brno University of Technology, Veveří 95, 662 37 Brno, Czech Republic, e-mail: pospisil.p@fce.vutbr.cz

Abstract:
Significance of optical study of cementitious materials (matrix and filling material) becomes very interesting and important during several last years. Study is focused not only on mineral composition of matrix in concrete but especially on petrographic characteristic of aggregates. Collection of 14 concrete samples was optically studied and petrographically characterized. Aggregates of these samples can be macroscopically divided in two groups, which mean that aggregates were formed in different geological environments. Because phthanites (Paleozoic silica rock) and porcelanites were observed in aggregates it had to be verified formation of ASR reaction products.

Key words: Thaumasite, concrete, degradation, petrographic characteristic, aggregate