In the pH range 0 – 7, the solubility of silica is constant, but above pH 8, the hydrolysis of siloxane bonds and deprotonation of silanol groups exponentially increase with pH. This is why glass easily dissolves at high pH and does not withstand extremely basic NaOH/KOH solutions. Therefore, NaOH/KOH released during cement hydration attacks and dissolves the tridimensional network of silica present in the aggregates. Amorphous or poorly crystallized silica, as cryptocrystalline chalcedony or chert present in flints (in chalk) or rolled river gravels, is much more soluble and sensitive to alkaline attack by OH– anions than well crystallized silica such as quartz. Strained (deformed) quartz or chert exposed to freeze-thaw cycles in Canada and Nordic countries are also more sensitive to alkaline (high pH) solutions.