Freeze-thaw cycle

The freeze-thaw cycle describes the climatic change in temperatures around the freezing point of water . In geography, the freeze-thaw cycle is responsible for the form of erosion caused by frost blasting , in materials science it represents a damage mechanism in minerally bound building materials . These materials have a porous, capillary structure and are not waterproof. If such a structure soaked with water is exposed to temperatures below 0 ° C, the water freezes in the pores . The ice is now expanding due to the density anomaly of the water. This leads to damage to the building material. In the very fine pores there is a lowering of the freezing point due to surface effects. In micropores, water only freezes below −17 ° C. Since the material itself expands and contracts as a result of the freeze-thaw cycle, there is also a capillary pump effect, which further increases the water absorption and thus indirectly the damage. The number of freeze-thaw cycles is decisive for the damage.

Freeze-thaw alternation attempt

An artificially induced freeze-thaw cycle is used as a test method for natural stones or building materials and is intended to provide information about the frost resistance of a material. One test method used in Germany is the CDF test .

The samples soaked in water at atmospheric pressure are exposed to at least ten freeze-thaw cycles, where they are cooled in air or in water to a temperature of around −20 ° C and then thawed in a water bath (+20 ° C). After the specified number of freeze-thaw cycles have ended, the changes in the specimens such as cracking, weight loss, chipping and, if necessary, changes in strength are determined.

Norms and standards

• Technical test regulations for minerals in road construction (TP Min-StB)
• Additional technical contract conditions and guidelines for the structural maintenance of traffic areas - concrete construction methods (ZTV BEB-StB)