Deterioration of Natural Stone by Freezing and Thawing in Salt Solutions

Some Swedish natural stones have been tested by freezing and thawing in water and in salt solutions. The tested stones were two different calcite bounded sandstones, one limestone and one granite. The used salts were NaC1 and Na₂SO₄.

Two different test methods have been used. A scaling test, where the damage is measured as weight loss after a number of freeze-thaw-cycles, and a dilation test, where the damage is measured as the permanent dilation after one single freeze-thaw-cycle. In the scaling test, the specimens are surrounded by solution during both freezing and thawing. In the dilation test they are wrapped in plastic foil. In the scaling test the effect of different salt concentrations was tested. The main purpose of the dilation test was to see the effect of the solution inside the material.

The results from the different tests contradict each other in several ways. This implies that the test method is of great importance. Results from the scaling test show that there exist pessimal salt concentrations and that limestone is extremely sensitive towards freezing and thawing in NaCl-solutions. Results from the dilation test show that dilation is negligible when the samples contain small amounts of solution and that it then increases drastically with increasing amounts of solution. The granite samples were almost undamaged in both test methods.