3 Key Forms of Concrete Deterioration


Concrete has more than earned its reputation as one of the toughest and longest-lasting of all building materials. In fact, many buildings which the ancient Romans constructed out of concrete still remain standing today. Yet, even with the general reliability of concrete, a concrete structure may still develop problems as time goes on.

As a matter of fact, concrete can fall prey to a number of problems that weaken it and lead to premature failure. Unfortunately, many people fail to appreciate the various ways that concrete deteriorates — let alone the ways that experienced contractors prevent it. This article takes a closer look at three key forms of concrete deterioration.

1. Scaling

Scaling, also frequently known as spalling, manifests as the flaking, peeling, or shallow chipping of a concrete surface. Scaling usually begins as a relatively small patch that grows progressively larger over time. Most scaling occurs as the result of natural freeze-thaw cycles.

When temperatures dip below freezing, any water in the surface turns to ice and expands by roughly 9 percent. This expansion creates internal pressure that makes the concrete far more vulnerable to flaking and chipping. A variety of factors determine how susceptible the concrete becomes to such freeze-thaw cycles.

For instance, concrete that was not correctly cured succumbs to scaling much more easily. Likewise, improper mix proportioning increases susceptibility to scaling. Specifically, too much water in a concrete mix tends to promote weaker bonds between aggregate particles, meaning the concrete won't have the internal strength necessary to resist scaling.

Certain concrete additives can also increase susceptibility to scaling. Fly ash, in particular, has been linked with increases in scaling, especially for concrete slabs installed during the winter months. In any case, fly ash content should never exceed 25 percent.

You can take several steps to reduce scaling in existing concrete slabs. For one, avoid using de-icing salts on the concrete — especially during the first year after placement. Instead, use sand to improve traction during snowy or icy conditions. Applying a penetrating sealer can also improve the concrete's resistance to scaling by blocking off the pores where water accumulates.

2. Internal Corrosion

As a building material, concrete itself cannot succumb to corrosion. Yet contractors use rebar and other embedded metal reinforcements to improve the strength of concrete slabs. These metals often experience corrosion as time goes on. According to one source, such corrosion ranks as the number one cause of concrete deterioration.

To understand why corrosion proves so destructive, you must understand what happens when steel corrodes. As you probably know, such corrosion causes rust particles to form on the surface of the steel. Those rust particles occupy a greater volume than the uncorroded molecules of steel.

Because the concrete packs tightly around the reinforcing metal, that corrosion doesn't have anywhere to expand. This unrelieved expansive force creates a large amount of internal stress. As a result, the concrete loses much of its resistance to exterior stresses. Scaling, cracks, and other forms of deterioration soon follow.

Unfortunately, contractors cannot do much to prevent corrosion once it has begun. The only effective way to limit corrosion is to avoid the use of corrosion-prone metals. Instead, contractors should choose rebar that has some form of corrosion protection. Epoxy-coated rebar and galvanized rebar both offer excellent corrosion resistance.

3. Delamination

Delamination occurs when the top 1/8 to 3/8 of a concrete slab becomes separated from the base layer by a skinny layer of either water or air. Delamination usually occurs as the result of poor installation, specifically during the finishing phase. Delaminations usually form during the final troweling process.

Of course, most instances of delamination do not rear their heads until long after installation has finished. At that point, the top layer of concrete may crack or sag as the result of inadequate support. Unfortunately, a contractor cannot do much to fix delamination once it has occurred. Instead, installation must proceed according to correct protocols.

To learn more about how an experienced company can install concrete that will hold up for years and years to come, please contact Albuquerque's industry experts at Star Paving Company.