The dissolution kinetics of (1-x) Si02.xCa0.25Na20.5Al203 glass (where x ranges from 0-25) are described in aqueous solutions buffered to pH7 at 90 deg C. The addition of calcium in this series of glass compositions appreciably modified the dissolution mechanisms, as demonstrated by the characterisation of glass samples altered for 60 minutes to 4 days in highly dilute media. Resonant nuclear reaction (RNR) and elastic recoil detection (ERD) analyses with energetic ion beams have been used to study hydration and ion exchange processes by measuring the hydrogen and sodium profiles of leached glasses. The hydrated layers were also characterised by scanning electron microscopy analysis, which corroborated the solution analysis and protons consumption results indicating a threshold effect with minimal alteration for about 10-15% CaO.
