Why Concrete Cracks (And What To Do About It)

Whether it's roads, driveways, sidewalks, or parking slabs, eventually, almost every kind of concrete cracks. It’s an inevitable element of the wear and tear suffered by a property - the same as paint peeling, garden plants dying, or walls getting dirty. Whether or not cracked concrete is a serious problem or just a cosmetic flaw depends on the type and location of crack. Let's look at some of the different ways concrete can break down.

Why Is My Concrete Cracked?

Plastic Shrinkage

Concrete in its non-solid state is basically just water and cement. As it hardens and the water evaporates, it shrinks. Too much water means too much shrinkage - and too much shrinkage leads to cracks in the finished project. This is usually a cosmetic flaw rather than a structural one. At the same time, if you want to avoid it, make sure you stick with the ratio of .5 - that means that for every pound or kilogram of cement, use half a pound or kilogram of water. If you want to use less, you can also add a plasticizer.

Expansion & Contraction

Like every solid, concrete tends to change subtly in shape and size based on weather conditions. Hot weather will see your concrete slab expand, pushing against anything in its path as it does so. If it meets an object that doesn’t flex or give during that expansion, it will likely crack. Unfortunately, aside from planning for this expansion, there’s not a whole lot you can do about this one. You’ll just need to repair the crack when the time comes.

Heaving & Settling

Generally speaking, ground movement is one of the most frequent causes of cracking, especially with sidewalks, driveways, and roads. The growth of a tree’s roots or an excessive freeze and thaw cycle can cause the ground to push upwards on the concrete, causing it to crack and break - a process known as heaving. Consequently, shifting in soil due to water or the rotting away of a tree’s roots cause the foundation of concrete to collapse - this is known as settling. As with expansion and contraction, heaving & settling is likely to occur over time.

Overload

If too much weight is placed on concrete, it can alter the ground beneath the slab, or simply break the slab itself. Make sure you’re aware of how much weight your sidewalk and driveway can handle. Otherwise, you might see pressure cracks or breakage.

Improper Drying

Last but certainly not least, crazing and crusting occur when laid concrete is improperly dried. The former results from concrete not having enough moisture or losing moisture too quickly, while the latter results from a pattern being pressed into concrete before it’s properly dried. Both crazing and crusting are entirely cosmetic - easily repaired and easily avoided.

When Should I Be Worried About Cracking?

Generally, cracked concrete is cosmetic unless it occurs in a supporting structure (such as a cement pillar) or it water gets into a crack when freezing occurs. Concrete that’s completely broken is also an issue in a sidewalk or driveway, as it can cause damage to a vehicle or injury.

How Do I Fix Cracked Concrete?

There are ways to repair some specific cases of cracked concrete, but in almost all cases your best bet is to call in professionals. We are able to assess the specific issues that caused your cracking and determine whether your best course of action is repair or replacement.