Hypothesis on the mechanism of ‘salt-frost scaling' of porous, brittle building materials

A hypothesis on the mechanism of “salt-scaling” of porous building materials is described. The hypothesis is based on theories on frost heaving in soils and observations made on micro ice-lens growth in cement paste specimens. The main principle is that ice crystals close to the surface are able to feed from the remaining liquid phase of the outer salt solution after freezing has begun. Though the text mainly deals with cement based materials, the mechanism described should be valid for any brittle, porous material. A simplified calculation in the form of a traditional calculation of depth of ice-lens growth shows that the hypothesis predicts reasonable values. The correct calculation is only briefly described. Results from a first pre-series test on water absorption during freezing support the hypothesis.