Aqueous durability of K2O-CaO-P2O5-SO3 glasses: kinetics and mechanism

The kinetics and mechanism of aqueous dissolution of glasses in 26K(2)O-24CaO-(50-x)P2O5-xSO(3) (0 <= x <= 30) composition is reported. Dissolution due to consumption of H+ and OH- was monitored using a pH stat titration technique. Solution analyses show dissolution to be congruent. Solubility is lowest in neutral solution and increases with increase or decrease in solution pH and with increase in sulfate over phosphate in the glass. These properties are explained using the cluster tissue model for glass structure. The dissolution process is controlled by phosphate clusters