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Finally the Truth about Spalling Concrete - What the "concrete guy" is not telling you

At RenuKrete, we have viewed, inspected and worked on thousands of concrete slabs and pool decks in the past ten years. The age of the concrete slabs and pool decks that we see ranges from a few months old to 50 years old or more! Frequently, when discussing the condition of the pool slabs with the current owner, it turns out that they were the original owner of the property when the concrete was poured, giving us unique insight into the behavior of concrete over many years and even decades. In contrast to "concrete companies" that pour concrete (and that usually do not come back ten or twenty years later to inspect the concrete), and in contrast to an individual or company that may have inspected a few concrete slabs but that has never actually worked on these slabs (RenuKrete has inspected and worked on thousands), the abundance of information we have collected gives us a unique expert ability to comment on concrete spalling, its causes, and ways to address spalling concrete. (We intentionally don't say "repair spalling" as is explained below)


Typical concrete section with spalling concrete surface
Typical concrete section with spalling concrete surface

Concrete spalling shows itself to the casual observer when the top layer of concrete starts to separate and disintegrate. The result is a weak surface, and concrete sections that break off without any or with little outside force. The spalling concrete sections are frequently the size of US currency coins, but they can also be the size of a palm.


The following facts are informed by:

  • thousands of inspections and data points

  • historical data

  • actual work performed on concrete slabs that show spalling


Truth #1: Concrete Spalling is like cancer in concrete


When concrete spalling occurs, it's similar to when the medical profession talks about cancer: it can never be said for sure what caused it, when it started, if it has stopped growing, if it ever stops, and how far it may travel. Similar to cancer tissue, spalling concrete can't really be repaired. It can only be cut out, and it's never 100% guaranteed that it doesn't hide somewhere in a different section of concrete, only to come back. Similar to cancer, spalling concrete can't be "fixed" by covering it up with something else (like a bandage on an arm).


Concrete section that was replaced due to excessive spalling
Concrete section that was replaced due to excessive spalling

Because concrete spalling is unpredictable, any work done using existing concrete can be impacted by it in the future, and thus can't be covered by any warranty if it's damaged or destroyed by the spalling base.


Truth #2: The cause? It's mostly speculation

There are many possible causes for spalling: a bad mix (too much sand, too little sand, too much portland cement, too little portland cement, etc), bad weather during the pour, insufficient curing prior to stress, and more. Since most pool decks are outdoors, the weather during the pour can be a significant factor in the outcome. 


When speaking with customers who watched the pour sometimes decades earlier, we usually hear something like this: When the first concrete truck showed up, the weather was fine. Then, when the last slab was poured, it began to rain and the contractor could not cover up the slab fast enough. Then, twenty years later, this same slab started to show signs of spalling.

Or this: "The contractor that day had too few guys on the job, since one of them called in sick. So, when the concrete trucks came, the crew had a hard time working the concrete into the forms, and finishing the surface fast enough. The result was that the concrete pour dried too fast for them (it was hot that day). In the area where they had problems, the slabs started to show signs of spalling ten years later."


Other historical information shows that salt can have a major impact on the tendency to see spalling occur, as does repeated exposure to urine from pets.


When the property owner has changed, it's unfortunately mostly speculation as to what could have caused the spalling to occur. But, it actually doesn't really matter: the course of action going forward is the same, no matter what the reason for the spalling.


Truth #3: Its a cover-up!

Unfortunately, sometimes, customers are advised by companies that sell overlays (see this article for general problems caused by overlays) to cover up the problematic areas with one of their products. Early-stage spalling can be hidden with overlays quite well, so that it is impossible to detect it. But, what at first may sound like a good idea (and it may last for a few years), then becomes a nightmare. If the disintegrating area underneath the overlay continues to get worse, it may lead to the overlay breaking up as well. Some examples that we have seen used to cover up spalling areas is Kooldeck, and sometimes even paint. Think of it like painting over dirt. Sounds like a good idea? Not to anyone who wants it to last more than a few days. It's the same with an overlay over spalling concrete. It hides a possible defect, but it's not really a fix. 


Truth #4: What about repair products from DIY stores?


Unfortunately, home improvement stores and even some websites are full with products that are sold for repair purposes of spalling concrete. They may be touted as “polymer reinforced cement” or have some other fancy names, but whatever they are, they do not address the underlying issue. All they do is cover up the spalling, as discussed in Truth #3 above. If the base underneath these patch products is not solid, they too will chip off sooner or later.


Truth #5: The best way to “fix” spalling concrete forever


As we have discussed, there is not really any way to “fix” spalling concrete. The best way to address it is by cutting out the affected area, and to pour new concrete. You may be thinking to yourself: “I will have a checkerboard look of new and old concrete across my pool deck, and I certainly don’t want to rip out the whole deck just to improve a few square feet of concrete.” You are right. Thankfully, RenuKrete has the solution for you!


Significant concrete spalling on the left. RenuKrete made the area look and feel like natural flagstone.


Truth #6: What RenuKrete can do about spalling


RenuKrete has helped countless customers improve their pool decks, and has often addressed spalling concrete along the way. When spalling is an issue, RenuKrete will recommend removing any loose concrete sections, in order to evaluate the remaining section. What comes next is really a judgment call that the property owner has to make, as nobody can say for sure if the neighboring section will be "good" or if it will start spalling in the future. Sometimes, it's best to cut out a larger section, and to re-pour new concrete. In this case, RenuKrete can blend the new concrete in with the old concrete section during the pool deck renovation.


RenuKrete, due to its unique technology that gives concrete the look and feel of natural stone, can offer an additional option that is much more cost effective. If the spalling is relatively minor and topical, and if the property owner prefers, RenuKrete can use the remaining solid surface and work it into its artwork. The result can be a wonderfully textured stone that blends in with its surroundings. As with all things spalling-related, the work can't be warrantied but if more minor spalling occurs in the future, it can usually be touched up within minutes, to appear just like another wonderful flagstone.


Spalling or not: If your pool deck has seen better days, and if you would like to turn it into a resort-style deck, check if RenuKrete can help and get your project started here: www.renukrete.com/getstarted


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