Concrete concepts: Raveling and spalling — what are they, and how can they be prevented?

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Raveling is when concrete starts to break apart at the surface level, with small rocks and chunks breaking away from the main body of the concrete installation. It is primarily caused by poor binding of the cement with the aggregate content of the concrete.?

Spalling is a similar issue, with crumbling occurring at the surface level. Spalling, often referred to as scaling, is typically caused by water infiltration into the concrete, which — especially during freeze–thaw cycles — can break up the concrete.?

Raveling in pervious concrete?

Raveling is more an issue with pervious concrete installations, though it also can affect standard concrete, primarily at the joints. If joints are sawcut into the slab at the wrong time — either too early or too late — raveling can occur along the edges.?

With pervious concrete installations, minor raveling is not a huge problem, as it has little effect on the function of the pervious concrete. However, extensive raveling can leave pervious concrete with an uneven surface, which can affect the look of the installation.?

With pervious concrete, raveling is most often caused by rapid evaporation. If the concrete dries out too quickly, the bond of the cement won’t be strong enough, and rocks may come loose from the surface after curing. Thus, it is important to pay close attention to the weather when pouring pervious concrete, as excessive sun or wind can cause evaporation to happen too quickly. This video offers great tips for decreasing raveling when pouring pervious concrete.?

Spalling in traditional concrete?

Spalling exposes the coarse aggregate of a concrete slab, such as a concrete driveway. Not only is it an eyesore, but it also can be a problem that gets worse with time, as spalling can open the concrete to easier water penetration.?

As noted above, spalling often is the result of freeze–thaw cycles in colder climates like Whatcom and Skagit counties. Water penetrates the concrete and then freezes, expanding and forcing the concrete to crack and flake away. Spalling also can be the result of corrosion of the metal rebar within the concrete, which also can cause cracking. The use of deicing chemicals also can cause spalling, because deicers can increase water penetration into already-stressed concrete. What’s more, the magnesium and calcium chloride compounds in many deicers can interact with concrete on a chemical level, resulting in problems like cracking, increased permeability and significant loss in strength.?

In the cases of both raveling and spalling, a high-quality installation from an experienced concrete flatwork company like Custom Concrete Contracting in Bellingham is your best defense. However, if you are experiencing spalling or raveling on an already-installed driveway, slab or retaining wall, please give us a call. We may be able to fix it just like new.?