Concrete Cracking and Failure Explained

To the untrained eye, concrete cracking and failure would appear to be the same exact thing. You’d be forgiven for thinking this, concrete cracking can absolutely indicate concrete failure, but more often than not, cracking in concrete happens naturally. We here at Royal Pools and G2 Outdoor Designs believe in transparency above all else, with that being said, you should know that there is a 99% chance that your concrete will crack eventually. It’s simply in the nature of the product. But concrete is known for being long-lasting and durable, right? Of course, but it’s dependent upon how properly your concrete was installed. It takes very specific processes to ensure that concrete will remain beautiful after the curing process. Perhaps you’ve noticed cracks in your own concrete and are concerned about potential repair costs. If this is the case, then this article is for you.

 

Concrete Failure: How Does it Happen? Can It Be Prevented?

There are many different indicators that concrete may be failing, if you know what to look for. You can break down concrete failure into two categories: resulting from poor installation, and resulting naturally from the elements. Failure is a much broader term than cracking, and refers to a lack of structural integrity to your concrete. As stated prior, concrete cracking usually occurs naturally, but we’ll get more into that later.

 

Concrete can fail for a wide variety of reasons, let’s take a look at a few.

 

• Pouring on frozen or uneven ground

• Freeze-thaw deterioration

• Weather

• Improper concrete mix

• Inadequate curing

• Design flaws

• Lack of Control Joints

• Chemical attacks

 

Pouring on frozen or uneven ground

One of the most important rules in pouring concrete is never pour on frozen ground. If it was possible to avoid ever having to pour on uneven ground, I’m sure concrete guys would find a way. Uneven ground in residential areas is often a result of poorly compacted soil, which is not what you want to be putting concrete onto. Concrete requires a solid foundation that it can sit flush atop without moving or sinking. If the soil is too loose, the concrete can end up shifting or sinking, creating a dangerous, uneven surface, or water that travels through the loose soil can seep into the concrete, causing it to expand and eventually crack. To prevent this, ensure that the ground upon which concrete will be poured is firm and flat. 

 

Freeze-thaw deterioration and Weather

Long-term exposure to the elements will affect any chemical mix, and concrete is no exception. Excess rainwater can build up underneath your concrete slab, and if the soil beneath the concrete is too soft and weak to support it, the slab can sink and shift out of place. Summertime heat can also heat up concrete so much to the point of expansion. But because the concrete is set in its position, the expansion leaves little room for actual growth beyond where the slab is, causing pressure buildup within the concrete, leading to cracks. And of course you have the winter when everything freezes. Moisture that seeps into or below the concrete can cause a couple of problems. If the soil below the concrete freezes in this time, the concrete slab could shrink and sink in on itself. If moisture enters the slab itself, that water can either freeze, creating expansion or throw off the concrete’s water ration, also creating expansion. Winter concrete maintenance is key.

 

Improper concrete mix

We cannot stress enough the importance of hiring concrete installers that are verifiably professional and as close to scientifically proper as possible. Inadequate installation will create a multitude of problems down the line that can cost you thousands of dollars in replacement and excavation fees. The concrete mixing and pouring process is fairly simple, but there are many small steps that if not done properly can create problems down the line. Concrete is essentially like glue, and you know glue eventually becomes hard. What makes concrete unique is that it requires water to bond the concrete to the adhesive, thus creating the material, this process is called hydration. Concrete does not require much concrete, typically around 20 pounds for every 100 pounds. Usually the concrete is pre-mixed before being sent to a job site, where the concrete workers may or may not add more water to this mix depending on if some slumps or slopes require a slightly looser mix. Concrete will not harden properly with a water-heavy mix, and weak concrete will crack in no time.

 

Inadequate Curing and Design Flaws

The concrete curing process is the process that the concrete undergoes after it is poured. This process entails maintaining a specific moisture and temperature of the concrete to ensure that it hardens to the specifications of that particular mix. The concrete needs a certain level of moisture application after the pour to foster quicker hydration within the mix. The curing process is done in two stages: the initial cure (which occurs during the finishing process), and the final cure. It is important to not skip either steps, as concrete with a surplus or lack of water will also not last long. Certain concrete designs require specific mixing and curing processes, but it is best to keep things as simple as possible when it comes to concrete. The more complicated a design, the more room for error.

 

Lack of Control Joints

Control joints are the designed cracks (typically between 1”-3” deep)  in the concrete cut in my the concrete workers to help control the direction and spread of future cracks. Control joints are put in at the discretion of the concrete cutters, and it should not be overlooked. A lack of control joints can lead to, you guessed it: cracking.

 

Chemical Attacks

Exposure to harsh chemicals like salt, sulfates, and various pool chemicals can cause concrete to fail as well. High sulfate water can enter the concrete causing sulfate crystallization within the slab, resulting in expansion which lowers the concrete’s structural integrity. Pool chemicals should always be stored away from concrete in a cool, dry area. 

 

Concrete Cracking: Can It Be Prevented?

As stated above, cracking is a natural, eventual occurrence in concrete. And as you now know, there are also multiple man-made reasons that concrete can crack. It is important to understand this because most people would be comfortable blaming the concrete workers for a bad job when in most cases the crack occurred naturally. Concrete can crack within hours of being poured, or it can crack five years after being poured. Concrete shrinks about ¼’ for every 100 square feet when its drying and a crack can happen at any time. It can be hard to determine why concrete may be cracking, or if it should be attributed to concrete failure, without knowing the difference between cracking and failure. Concrete workers and manufacturers do the best they can to ensure a durable, long-lasting product, but unfortunately there is no fool-proof method to prevent concrete from ever cracking.  New and exciting technological advancements are being made every day, hopefully one day concrete that doesn’t crack will be a possibility. For now we make do. 

 

Types of Concrete Cracks

Below are photos of different types of concrete cracks and their names, indicating how the crack occurred. 

Shrinkage Cracks

Settlement Cracks

Heaving Cracks

 

Hairline Cracks

Cracks Resulting From Weight Overload

 

Written By Logan Edgemon

 

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