SCALING CONCRETE SURFACES
What is scaling?
Peeling or flaking of the finished surface of hardened concrete is known as “scaling” and is caused by freeze/thaw cycles. Light scaling does not expose the aggregate, while moderate and severe scaling will do so.
Why do concrete surfaces scale?
Saturation of the concrete in near-freezing temperatures causes stresses in the concrete when the water expands during the transition to ice. Deicing chemicals increase the potential for damage by increasing both the saturation at the surface of the concrete and the overall number of freeze/thaw cycles.
How to prevent scaling:
The best method to decrease the potential for scaling is to use dense concrete with entrained air, follow good practice for placing and curing, and minimize the use of deicing chemicals. Entrained air concrete contains incredibly small air bubbles that allow freezing water the space it needs to expand without damaging the concrete structure. When the concrete is installed, do not overwork the surface during finishing as doing so reduces the air content in the concrete. Keep all deicing agents to a minimum, and avoid ammonium sulfate, ammonium nitrate, and all magnesium based deicers as these will chemically attack and destroy concrete surfaces.
How to repair scaled surfaces:
Light to moderate scaling may be repairable. Keep in mind that the repaired surface will only be as strong as the underlying base. All surfaces to be repaired must be free of dust and other debris of any sort. Repair work will not match the original color or characteristics of the concrete.
Adapted from IRMCA – CIP 100