Tests on silica for specimens without pre-existing stresses

At silica surface exposed to a water environment, the water reacts with
silica. Experiments show that the hydroxyl generation has an influence on
mechanical properties. We dealt with these effects in the past and could in-
terpret them as a consequence of swelling in the surface region. A different
attempt was suggested in a series of publications by Tomozawa and co-
workers assuming relaxation of stresses due to presence of water.
Since any stress relaxation needs pre-existing stresses, we will here only
discuss results which were obtained in the absence of any present stresses.
We consider density, disk-deformation, and inert strengths. These results
show a strong effect of hydroxyl content and can be understood by the ef-
fect of swelling. Finally, a suggestion is made for further studies on swell-
ing.