Abstract
The shrinkage stresses due to drying and the differences of volume changes and rigidities between the two phases of dense Ca(OH), crystals and porous C‐S‐H gel are estimated. High tensile stresses are calculated around the Ca(OH), crystals at a relatively high humidity. It is also shown by a calculation on the basis of some assumptions that the shrinkage stresses may cause microcracks which drastically increase permeability.