X-ray diffraction analysis of an alkali-aggregate reaction

The Alkali-Aggregate Reaction (AAR) is a physico-chemical process of intern al damage of concrete. The concretes damaged by this reaction are constitut ed of alkali-reactive aggregates. These aggregates have quartz phases with internal flaws called silanols. AAR development within aggregate involve an increase of internal silanols number. To study this structural transformat ion, we have followed the evolution of X-ray diffraction peaks of quartz ph ase as a function to reaction degree. The flint aggregate shows high ray width at half medium which traduces the presence of internal silanols. As the reaction progress we observe a decrea se of ray width at half medium and surface of diffraction peaks. We interpr et this result like the transition of zones with internal flaws in amorphou s zones. The best crystallized zones are progressively revealed by the atta ck.