Examinations of the structure of highly polymerized alkali containing C-S-H phases

Cement is an inorganic hydraulic binder widely used in civil engineering. By the reaction of cement with water calcium-silicate-hydrate (C-S-H) gel is the principal hydration product For example, building materials based on Portland cement could contain up to 70 wt% C-S-H gel. Therefore, the structure of the C-S-H gel is responsible for the mechanical properties of the hardened cement paste. The chemical compostion of C-S-H gel varies between the molar CaO/SiO 2 (C/S) ratio of 0.5 in older and partly carbonated hardend cement paste and 2.2 in fresh ones. Reaction products (alkali containing C-S-H gels) of the deteriorative alkali-silica-reaction (ASR) show an even lower Ca content. Additionally, these gels have a significant amount of alkalis. Their formation processes and the reaction mechanism of ASR are still unknown and a subject of investigation.