Concrete Cracks and How to Repair Them

When someone sees cracks in their freshly laid concrete, they may be worried. After spending so much time and money on having the concrete mixed, installed and dried, it can seem like the cracks ruin the entire project. However, cracks do not always indicate that there is a problem. There are three main types of concrete cracks, not all of them require concrete hairline crack repair.

Shrinkage and Expansion

Water is used in concrete; as the water in the concrete dries, it decreases in size. These cracks are usually very thin and barely visible. The more water that is used in the concrete, the more shrinkage that will occur. Similarly, cracks can also be caused by the concrete expanding. Expansion tends to happen in hot weather, while shrinkage tends to happen more in cold weather. The initial shrinking of the concrete as it dries all but solidifies the size of the slab itself.

Movement

As the ground under the concrete thaws or freezes, it causes the concrete slab to move. For instance, if there are several inches of snow, ice may build up beneath the concrete causing it to move and crack. Additionally, when the ice thaws, it can cause the concrete to move again. If the concrete is installed near trees, roots that grow and/or decompose beneath the concrete may cause it to crack as well.

Overloading

Concrete is installed in so many areas because of its ability to hold lots of weight. However, concrete can only handle a certain amount of force. If the concrete is overloaded with too much weight or force, it can cause the concrete to crack as well.

Repair

Cracks created by shrinkage and expansion do not necessarily need to be fixed. They usually do not impede the function of the concrete and they are typically very thin. But larger cracks, like those caused by movement and overloading will most likely need fixing. Concrete hairline crack repair is not as difficult as it may seem. First, it is necessary to clean the crack with a chisel and hammer and to brush away any extra dust; this will ensure that  the crack is clearly defined. Larger pieces will need to be vacuumed out of the area. The next step is to fill the crack with a cement patch and to let it dry for the recommended amount of time. The final step is to seal the patch with a water based polyurethane.