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What Causes Concrete Spalling?

By Sarah Etler - 10/24/22, 1:30 PM

Learn about the most common causes of concrete surface spalling and your options for dealing with it.

If you’ve noticed indents and imperfections in your concrete, the best thing you can do is take action to slow down their progression. But what actually causes them to appear in the first place?

Knowing how your concrete may have ended up with surface spalling can help you come up with a plan of action to mitigate those factors and preserve your concrete.

This article will guide you through what spalling is and its main causes, as well as give some insight on what you can do to slow it down if it does happen to your concrete surfaces.

What is concrete surface spalling?

Concrete spalling is the deterioration of the concrete’s surface, usually appearing as chipping, flaking, or peeling sections. These sections can be small, affecting only one small part of the concrete, or they can take over an entire slab.

Read “All About Concrete Surface Spalling

What causes concrete spalling?

Here are some of the common causes of concrete spalling:

1. Freeze-thaw cycles

Because concrete is porous, it can easily absorb water. This becomes a problem when that water gets absorbed, freezes, then expands, causing the pores of the concrete to pop. When this happens, it causes the surface of the concrete to deteriorate and spall. 

As the temperature drops above and below freezing, it creates a continuous freeze-thaw cycle that allows more and more water to be absorbed, freeze, and cause damage to the concrete’s surface.

2. Poor-quality concrete

When manufactured correctly and maintained properly, concrete can last decades. However, if the concrete mix isn’t created with the right ratios when at the factory, it can cause a heap of problems throughout the concrete’s lifespan, including spalling.

Usually, poor-quality concrete lacks the right amount of a key ingredient: portland cement. This ingredient is what makes concrete extraordinarily strong, and a ratio without enough portland cement can cause concrete deterioration. 

3. Deicing salts

The difference in pH between salt and concrete causes deterioration when the two come in contact with each other. Because salt mixes with water and gets absorbed into the concrete’s pores, it breaks it down from the inside and causes damage, like surface spalling. 

Salt can also pull more water into the pores of the concrete, worsening the effects of the freeze-thaw cycles. Using deicing salts is convenient, but it’s not the best for the longevity of your concrete.

4. Corrosion & oxidation of rebar

If the rebar within your concrete becomes exposed and comes into contact with water, it can cause rust and corrosion. This oxidization produces a chemical reaction that causes concrete to deteriorate in forms like spalling.

Your Options for Surface Spalling

Cleaning and sealing your concrete from the beginning of its life can help prevent spalling in the first place, but if you haven’t had the chance to do it from the start and spalling has set in, here are some of your options for addressing it. 

Concrete Overlays

Pouring a thin layer of concrete on top of the indented and spalling surface can improve its appearance for a little while, but it will start to chip away not long after being applied.

Because the source of the deterioration isn’t being treated, the spalling will continue to worsen and eventually force the overlay layer to chip and crumble along with it.

Spalling concrete covered with an overlay that is chipping away

Topical Sealers

Many people believe that covering their spalling concrete with a thick topical sealer will prevent further deterioration and improve the look of their concrete, but that’s not the case.

Applying a tinted topical sealer on the concrete won’t stop the spalling from worsening, and it will likely cause ugly white splotches to appear over time as the deterioration continues.

Concrete slab covered in white spalling patches

Concrete Replacement

In order to fully eliminate concrete surface spalling, total replacement of the affected slab(s) is the only complete solution to the problem. While this is true, installing new concrete comes with many other risks, along with the hassle and headache of replacing concrete.  

If you do end up replacing your spalling slabs, you have to make sure to select a good contractor to minimize the potential for issues that could cause spalling on the new concrete, and make sure to seal it as soon as possible after installation.

Penetrating Sealer

A concrete sealer that penetrates deep into the pores of your concrete is the best bet for slowing down the progression of the existing spalling. 

While not a complete guarantee that it will completely solve your spalling problem, its chemical reaction binds with the capillaries in your concrete to create a barrier that protects from moisture, freeze-thaw cycles, and the other causes of spalling.

Here at A-1, we like to think of cleaning and sealing your concrete as equivalent to waxing your car and changing its oil. Changing your oil, like sealing your concrete, does not guarantee that you are never going to have an engine problem, but it does help the longevity of your vehicle, and it can help reduce the likelihood of having to completely replace your engine down the line. 

Waxing your car, like cleaning your concrete, is something that you don't have to do all the time, but it can help protect your paint and makes your car look new again. 

Now what?

Now that you know about concrete spalling’s main causes, you’re ready to assess your own concrete and consider the options you have for dealing with it.

Regardless of the reason, concrete replacement is the only way to truly eliminate surface spalling, but because of the risks involved, cleaning and sealing your concrete with a high-quality penetrating sealer is a great alternative. 

A-1 Concrete Leveling offers this service, along with other concrete repair options, to get your concrete looking great and functioning the way it should.

Click the link below to request a free consultation and estimate!

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