What Causes Concrete to Crack?


If you’re like many Americans who grew up in the suburbs, a favorite childhood pastime of yours was probably riding bikes with your friends throughout the neighborhood.

If so, you probably knew your cul-de-sac like the back of your hand – where all the best hills were, which neighbors set up sprinklers you could ride through, and of course, where all the biggest sidewalk cracks and potholes were lurking – you had the knee scars to prove it!

If concrete isn’t properly maintained, it can lead to problems down the road… literally.

The Truth About Concrete Cracks

What causes cracks in your concrete? Well, cracks are virtually unavoidable, unfortunately. Why? It all stems from one of its key ingredients: water.

Think of a sponge, perhaps the one sitting by your kitchen sink, ready to help you wash dishes. When it’s full of water, it’s quite plump and is the fullest and largest it can get. When you wring it out and it dries completely, it shrinks. Concrete functions in a similar manner.

When the water in concrete evaporates; it’s bound to crack.

In addition to the aforementioned, other factors also affect your concrete, such as tree roots, loose soil, and natural disasters, to name a few.

Why Does Concrete Crack?

Although cracks are inevitable, there are reasons in which cracks may be more prevalent in certain areas. Some of the biggest reasons are as follows:

Too Much Water in the Concrete Mix

When mixing a concrete solution to be poured, some water is required. Water is one of the key ingredients in concrete, and a mix with excess water yields a more malleable consistency, therefore making it easier to install. However, this short-term benefit is not worth it when you consider the long-term consequences.

Too much water in a mix will cause big issues because as the concrete dries, the water evaporates. This causes shrinkage, which in turn creates cracks in your concrete.

Worse yet, in addition to cracks, a watery mix severely diminishes the durability of your concrete.

Concrete Dried Too Fast

In the above example, we saw what happens when there’s too much water in concrete. What happens if you have too little?

As concrete dries, it goes from a liquid state to a solid state; it’s a chemical reaction that must be properly facilitated.

The curing process is vital to creating and maintaining the structural integrity of your concrete. When cement mixes with water, hydration begins and crystals form, which bonds everything together to create the stone-like consistency that we call concrete.

Although concrete is usually safe to walk on after 24-48 hours, the full curing process can last up to a month, depending on the size of the slab, the specified cement strength, the mixture itself, and weather conditions.

During the curing process, the concrete solution must have ample opportunity for crystals to grow and for the mixture to dry evenly throughout the slab. For it to cure properly, water must be added to the top throughout the process to ensure adequate moisture for long-term hydration and strength, as well as resistance to weather-related factors.

Therefore, if concrete is drying on an extra windy or hot day, rapid drying can occur. This makes the chemical reaction happen too fast, and therefore the long-term strength is negatively impacted.

Cold weather presents its own challenges. But that’s a topic for another day.

Improper Strength of Concrete

Another reason for cracks to occur in your concrete is if the wrong strength of concrete was mixed in the first place, or if the original intentions of the poured concrete change later down the line.

For example, if your driveway was made to accommodate only standard-sized vehicles, cracking is very likely to occur if you start storing exceptionally heavy loads, such as a dumpster full of hefty construction debris. The same can occur on streets that are meant for standard vehicles only, rather than hefty semi-trucks.

Although the damage may be severe, rest assured, you have many options for restoring your driveway to a strong, healthy state with stunning curb appeal.

Wrongly Placed Control Joints

Have you ever wondered what the lines are in your sidewalk? No, they’re not for design; they have a unique, valuable purpose.

According to Concrete Network, “Control joints are planned cracks which allow for movements caused by temperature changes and drying shrinkage. In other words, if the concrete does crack – you want to have an active role in deciding where it will crack and that it will crack in a straight line instead of randomly.”

It can be difficult to predict the precisely perfect locations for these control joints, and even still, it’s not a guarantee that cracks won’t occur. Hence, another reason for cracking to arise.

Fun fact – these are also known as relief points or contraction joints.

Request a Free Concrete Repair Estimate

At Joco Foam Pro, we specialize in all facets of concrete repair for not only homeowners, but also businesses and municipalities, too. We’re a family-owned business whose passion is helping our community take pride in their home or business, through affordable, long-lasting concrete repair solutions.

Ready to fix your sinking, settled, or uneven concrete? Reach out to us today for a free concrete repair estimate and we’ll be delighted to help you come up with a plan that best works for you.