Water diffusion into silica glass results in a thin zone near the surface of the glass. In this zone molecular and hydroxyl water are present. The content of hydroxyl water increases its specific volume so that the silica expands and the volume near the surface is larger than it was before being penetrated by the water. Suppressed free expansion of the glass causes biaxial compressive swelling stresses.
The effect of such swelling stresses and also of moderate externally applied stresses on the diffusion behaviour will be studied in this report for the case of a gaseous water environment at temperatures <500°C.
In the Appendix also the effect of stress-enhanced equilibrium constant is addressed and the behavior at higher temperatures briefly considered.