Why is my garage concrete floor cracking

Have you noticed tiny hairline cracks appearing on your concrete floor? With time these tiny cracks become longer and wider, until the point where pieces of concrete start falling off. By why is this happening and how can we fix it?

Why is concrete cracking in my garage?

There can be numerous reasons why your concrete floor might be cracking. While most of the cracks might not be a structural concern, they can definitely be an aesthetic one. Generally speaking without a proper inspection, it is hard to determine what is causing the concrete cracks. Some of the main ones are:

Poorly constructed concrete

Water plays a vital part in every concrete mix. But there is also such thing as too much water in the mix. An excessively wet mix is a major reason for concrete shrinkage. The slab shrinks more when the mix contains too much water, eventually leading to shrinkage cracks.

The way the concrete has been laid and the weather

The way the concrete is laid and the weather can play a vital role in the concrete strength. On sunny or windy days where the top of the slab dries out quicker than the bottom, the top of the concrete surface can become crusty, leading to the potential hairline and shrinkage cracks.

Hot weather and heat also cause the concrete to expand. When the concrete expands, it pushes against anything in its way. As neither the concrete nor the walls are flexible, this results in cracking.

The ground underneath

If the ground was not properly prepared for laying the concrete, can lead to an unevenly laid surface, distribution of weight, and movement. Some minerals in the soil can react with the concrete, by soaking through it and potentially leading to cracks.

If you leave in a cold area, in winter when the ground freezes, it can sometimes lift substantially before defrosting and settling back down. The ground movements caused by freezing and defrosting can contribute to concrete cracking if the concrete slab is not free to move with the ground.

No joints in the concrete

Expansion joints in the concrete can prevent the concrete from cracking. When the concrete is expanding due to heat, they can serve as shock absorbents to relieve the stress that expansion puts on the concrete.

Control joints, on the other hand, can prevent shrinkage cracks, by opening up as the concrete gets smaller.

Concrete cancer

When the steel reinforcing rods in the concrete slab start to rust, they cause so-called concrete cancer. As the steel rust expands, it displaces the concrete around it, causing it to become brittle and crack. One of the main signs of concrete cancer is rust stains leaking out from within the concrete.

Overall the main reasons why concrete slab cracks are related to wrong ground and concrete mix preparation, shrinkage, heat, wrong joint placements, over stress, and movements.

Can Garage Floor Cracks Be Repaired?

If the garage floor crack is structural, wide enough, or due to corroded steel, then it is best to consult with an engineer for the available repair options. For any other concrete cracks, where the problems of cracking have been solved, one of the most popular concrete repair methods is epoxy injection followed by epoxy coating.

To fix the crack, it is best to diamond grind the floor. Then vacuum the floor and the cracks, removing all dust and debris from it. Sometimes a leaf blower does wonders for blowing everything out of the cracks.

Once the crack and the area around have been prepared, epoxy is injected into the crack. The epoxy glues everything back together by bonding to the prepared concrete. Engineers recommend this method before ripping everything off, as epoxy is 3 times stronger than concrete.
As a final step, of protecting the concrete slab, an epoxy flooring system can be laid on top. The epoxy will act as a bandage, keeping everything together. It will also be more aesthetically pleasing, as it will hide the stops where the garage floor cracks have been repaired.

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