The Science Behind Why Sidewalks Crack!

Whether its driveways, roads, parking slabs or sidewalks almost every kind of concrete eventually cracks. It’s an unavoidable element of the wear and tear suffered by all concrete made materials.

Well, a cracked sidewalk is a serious problem. However, the seriousness depends on the type and location of the crack. Let’s have a look at some possible ways sidewalks can crack.

The Science behind Sidewalk Cracks

Due to temperature change, concrete expands and contracts just like many other seemingly indestructible construction materials.

Let’s look at it this way: think of your sidewalk as one continuous slab. In the morning, when the temperatures are low your solid continuous slap will contract.

With the day aging, the sun intensity heats up the sidewalk causing the temperature to rise making it to expand. With no expansion room, the concrete will be forced to crack. To avoid cracking, expansion joints are incorporated to provide the concrete with expansion and contraction room.

Categories of Slab Cracks

1. Plastic Shrinkage Cracks

Generally, this occurs when the slab loses water faster than anticipated, such that the top side dries more quickly than the bottom side; inducing a tag of war between the two sides. Mostly this happens during an extremely windy or hot day.

To avoid this, moisture the surface by placing wet towels, burlap or mats on the concrete. Sprinkling water on the surface can also do the trick.

2. Settlement Cracks

This kind of cracks are caused when the ground below the concrete shifts. Earth shifting can be as a result of water erosion, tree roots, poorly compacted soil or even wrong kind of soil (sand)

3. Drying Shrinkage

Cracks may occur when a restrained slab is drying and shrinking. To avoid this, ensure that the slab is free during the drying process.

4. Chemical-Induced Concrete Cracks

There are two possible ways that chemical reactions can cause your sidewalk to crack:

  • Due to incompatible cement in the concrete, the slab may crack. However, this should not worry you much as contractors are always keen on the cement they use.
  • Secondly, your sidewalk may crack due to exposure to elements. Substances like HCL, Sulphur, and salt may catalyze the weathering process, creating deep engraved cracks on the slab.

So, Why do Sidewalks Crack?

Despite employing exquisite construction skills, you will still find your sidewalk chronically infested with surface cracks. Some causes are including:

1. Poor Construction

Among the numerous construction errors related to sidewalk cracks include; using incorrect cement to blending the cement mixture and improper slab curing, making it develop permanent structural defects.

2. Extreme Weather

Despite employing the best engineering techniques, slabs may eventually yield to Mother Nature’s wrath. Extreme temperatures can cause the slabs to continuously expand and contract to result in surface cracks. In the Arctic and the equatorial regions, an adverse temperature is the main cause of sidewalk cracks.

3. Air Pockets

In other cases, empty spaces in the soil below the slab can lead to cracks. This mostly happens when the slab rests on uneven ground that has not solidly compacted, creating empty pockets of air. Over a period of time, soil settles into the pockets. Since soil is not strong enough, it offers inadequate support causing the slab sinks and eventually cracks.


Well, guys, there are only two beings, who may responsible for the cracks in your sidewalk; either the contractor or yourself. So, next time you are out looking for someone to fix your sidewalk, make sure to get a qualified contractor; otherwise your sidewalks will never get any better.

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