Freeze-Thaw

Summary

Freeze-Thaw - is a form of physical weathering.

Technical Information

Freeze-thaw weathering is caused by water present in the pores of the concrete and freezing in cold weather conditions. Because water expands when it freezes, it exerts an expansive pressure on the pores. If this expansive pressure overcomes the tensile resistance of the cement surrounding the pores, the cement will crack and parts of it will break off. The more permeable a concrete is, the more susceptible it is to freeze-thaw.

This form of weathering may not be recognised immediately, as it may need to cycle many times before the damage becomes visible.

Freeze-thaw can be limited by:
Increasing the tensile strength of the concrete
Reducing the permeability
Introduce an air-entraining agent – the small bubbles introduced to the paste allow additional chambers for the water to expand into – this is not common in internal ground floor slabs.

The use of some cement replacing materials can also affect the curing of the concrete in colder seasons. While they can enhance the concrete’s properties, if they also increase curing time, which may encourage freeze-thaw whilst the concrete is setting.

If freeze-thaw is a concern during curing, blankets can be used to regulate the temperature of the concrete until it is set.