Anisotropic Swelling for different Stress States

Water reacting with silica causes the generation of hydroxyl SiOH accompanied by a volume or swelling expansion. The principle of LeChatelier ensures that the hydroxyl concentration increases with increasing externally applied stresses. From the analysis in [1] it becomes obvious that
a) the hydroxyl concentration must depend on the multi-axiality of the applied stresses, and
b) that the swelling effect is anisotropic.
On the basis of the results in [1] it will be shown that under torsion loading the strongest effects should occur.