Spalling: Concrete Driveway and Walk Damage

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Damage to driveways like the one pictured here in Castle Rock, Colorado, can be caused by several factors. This condition, commonly referred to spalling, is as a result of the finished layer of concrete separating from the core layer of cement, exposing the interior  elements with large stones and concrete mix.
Generally, spalling is more prevalent where moisture collects the most. While walkways are often cleared of snow and ice during the winter, it may not be cleared off other surfaces. This can lead to additional damage on those areas. With respect to concrete sidewalks, patios, stairways, and similar outdoor concrete, spalling is most commonly caused by two factors:

Moisture and Temperature Changes

Concrete is a porous, absorbent material. Water will be absorbed within the material. During cold weather, this moisture will collect between the finished top surface of concrete and the rough material underneath.

Water expands as it freezes. As the water expands within the concrete, it pushes up against this smooth concrete surface. Over time, this will cause the surface to come off exposing the core material inside which is rough in texture as noted.

Improper or Excessive Use of Concrete De-Icer

De-icers and rock salts should be spread lightly on icy concrete surfaces, so they can loosen the concrete and make it easier to remove. It’s expected that the de-icer will be removed along with the snow and ice it helps to melt.

When this doesn’t occur after application, the de-icer may seep into the concrete along with the moisture. It then lowers the freezing point of water and can lead to additional freeze/thaw cycles when the temperature drops. Additionally, rock salt will remain as the water evaporates, crystallizing beneath the surface. As these rock salt crystals build up, they can push up on the concrete surface as well, contributing to spalling.

Always make sure to keep concrete surfaces clean, and using a sealer will help prevent this water penetration. Making sure to remove salt or de-icers after application is a must.