Petrographic Study of Siliceous Aggregates. Parametric Calculus of the Reactivity with the Alkalis

The microstructural stability of some components of aggregates is one of the determinants of the durability on concrete structures, regardless of their characteristics and intrinsic properties. Some pathologies such as alkali-aggregate reaction are linked with certain siliceous phases. Depending on its reticulated structure, the siliceous phases can provide siloxane groups to the media and promote nucleation of expansive gels, favouring the deterioration of concrete. The petrographic identification of the stress state is based on the physical property of the light polarization, which give defined optical results in deformed crystals. The digital imaging techniques allow to extract and to quantify these areas, establishing quantitative parameters that correlate exhibition area of siliceous aggregates edges with areas of fixation and development of expansive products.