What Is Spalling?

Malcolm Tatum
Malcolm Tatum
Malcolm Tatum
Malcolm Tatum
Spalling concrete shows pits and cracks.
Spalling concrete shows pits and cracks.

Also known simply as spall, spalling is a term used to describe the process that occurs when flakes are separated from some type of larger body of material. The separation can be caused by many different factors, including the natural process of weathering, corrosion, continual friction, or a direct impact with another object. Many materials used in machinery are subject to some degree of spalling, as well as many types of building material.

One of the more common types of this sort of activity is known as mechanical spalling. Often, friction and direct impact with other components in a piece of machinery results in the creation of small flecks of metal. One excellent example of a mechanical spall is the friction that a ball bearing is subjected to when a machine is in active use. The constant friction and impact with other bearings help to create the small flecks, gradually wearing down the bearings until they must be replaced.

In terms of spalling activity that is related to building materials, concrete and brick spalling are two of the most common examples. With both materials, exposure to changing temperatures, rain, snow, sleet and other weather conditions gradually wears on the surface of the construction, producing flakes in the process. Both brick and concrete spalling take place in just about any type of climate, although the rate of flaking is accelerated in areas where weather conditions are particularly harsh for most of the calendar year.

With some forms of spall activity, it is possible to repair the damage. This is particularly true with concrete. The process of concrete spalling repair usually involves the addition of a new façade to the concrete, effectively replacing what was worn away over time. As similar approach to repairing spalled concrete can be used to repair bricks that have been worn down by the flaking action.

At other times, replacement is the only option when spalling has rendered the object unsuitable for continued use. Ball bearings are replaced from time to time, since there is no reliable method to resurface the bearings and restore the quality that a newly minted bearing possesses. Metal panels that have deteriorated due to flaking may also be unsalvageable, and require replacement rather than refurbishing. Generally, people who are charged with the responsibility of maintaining machinery or the exterior of buildings will know when repair can be effective, and when replacement is necessary.

How To Fix Spalling Concrete

When you have spalling concrete, also known as scaling concrete, there are a few different ways to go about fixing it. The method of repair will depend in large part on how much spalling is occurring, both in surface area and the depth of the spall.

The first method of fixing spalling concrete is by using a concrete patching compound. These usually contain polymers, concrete, and other additives, including a tint to match the color of your current concrete.

Spread the compound over the spalled area, being sure to overlap the good concrete on all sides of the bad spots. The compound will bind to the existing concrete, strengthening it to help prevent future spalling.

The second method of repairing spalling concrete is to resurface your concrete with an overlay. An overlay is a whole new layer of concrete on top of the concrete that’s spalled.

To prepare for an overlay, you need to clean your current surface and patch any cracks. Then a professional can come in, apply the overlay, and even stamp it to give it the appearance of wood, natural stone, slate, or bricks. Even without stamping, it’s a good idea to have a professional do the overlay, due to the size of the concrete that needs to be re-covered.

The third way to repair spalling concrete is to remove the entire slab and replace it. This is the last-ditch option for when your concrete is so badly damaged that no other fix will work successfully.

Ripping up a concrete slab and replacing it is definitely not a do-it-yourself job. Call several reputable concrete contractors to get multiple quotes for the job. Read reviews and ask friends for referrals to contractors who may have taken care of their concrete issues.

What Causes Concrete Spalling

Concrete spalling can occur due to a variety of factors. All concrete will crack; it’s just a matter of time. The degree of cracking may be preventable.

Freeze-Thaw Cycles

When you live somewhere with cold winter weather, your concrete may go through several freeze-thaw cycles every year. Moisture from ice and snow can wreak havoc on your concrete, especially if you use de-icing salts on your concrete surfaces.

During winter, water seeps into the cracks and crevices in your concrete surface during the day. When nighttime brings lower temperatures, that water freezes, expanding in volume by 9%. This expansion stresses the concrete, spreading out its openings and creating wider gaps in the surface of the slab.

This process repeats over and over when daytime temperatures rise, melting the ice and snow, and nighttime temperatures plummet. Every time, the crack expands with the water, creating larger and larger cracks. Eventually, concrete will begin chipping off of the slab in pieces.

A couple of things can help prevent spalling from freeze-thaw cycles. The first is air entrainment, when air bubbles are intentionally added evenly throughout the concrete, giving water space to expand without pushing against the concrete itself.

The next method is to use certain de-icing chemicals that lower the freezing point of water. Sodium chloride is the most commonly used de-icer, but you have to be careful to keep it off your lawn and other landscaping, as it can burn plants.

A third means of preventing freeze-thaw damage is to apply a sealer to your concrete after it’s done curing. Sealers stay on top of the concrete, preventing water from making its way down into the slab. They usually need warmer weather to seal your concrete fully, so it’s best to apply sealants in summer. Sealant should be applied every few years to keep your concrete from spalling.

Improper Concrete Pouring

If your concrete is mixed or poured incorrectly, it may be more prone to spalling. It’s often advisable to hire reputable concrete professionals to pour your concrete, as they’ll have expertise in their field. Some mistakes include:

  • Concrete mix is too wet
  • Concrete mix is too dry
  • Using a weak concrete mix
  • Pouring too thin a slab
  • Thinking reinforcement mesh will prevent spalling
  • Not using reinforcing fibers
  • Using reinforcing materials that can rust
  • Using cement that’s more than a year old
  • Not troweling at the right time
  • Pouring concrete when it’s humid or near the first frost
  • Using weak or inefficient forms

With enough attention paid to the details, a do-it-yourselfer may be able to pour a sturdy concrete slab that won’t spall for several years, if ever. When spalling does occur, it may be a do-it-yourself fix, or you may need to call in a professional, depending on the size of the spall. Remember, all concrete cracks eventually, but spalling can be largely prevented if enough care is taken to pour your concrete correctly.

Malcolm Tatum
Malcolm Tatum

After many years in the teleconferencing industry, Michael decided to embrace his passion for trivia, research, and writing by becoming a full-time freelance writer. Since then, he has contributed articles to a variety of print and online publications, including AboutMechanics, and his work has also appeared in poetry collections, devotional anthologies, and several newspapers. Malcolm’s other interests include collecting vinyl records, minor league baseball, and cycling.

Malcolm Tatum
Malcolm Tatum

After many years in the teleconferencing industry, Michael decided to embrace his passion for trivia, research, and writing by becoming a full-time freelance writer. Since then, he has contributed articles to a variety of print and online publications, including AboutMechanics, and his work has also appeared in poetry collections, devotional anthologies, and several newspapers. Malcolm’s other interests include collecting vinyl records, minor league baseball, and cycling.

Discussion Comments

shell4life

@Starjo - You need to cover the whole area that has spalled in a polymer-modified overlay of a color that matches the concrete of your driveway. After the overlay has cured, then you need to put a waterproofing sealer on it to guard against future spalling.

StarJo

How can I fix the damage caused by spalling in my concrete driveway? It has flaked off quite a bit, and I know it is too late to simply take preventive measures.

Perdido

Using a sealer for concrete can help prevent spalling. Penetrating concrete sealers react with the concrete chemically and provide protection from moisture and the chemicals used for deicing sidewalks. Film-forming concrete sealers, often used in decorative concrete, form a shiny film on its surface to improve its appearance as well as promote its longevity.

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    • Spalling concrete shows pits and cracks.
      By: peter hollander
      Spalling concrete shows pits and cracks.