Cracking Concrete: What Causes It and How to Fix It

Cracks in concrete are a common occurrence, and they develop when the stresses in the material exceed its strength. This is usually caused by normal shrinkage of concrete as it hardens and dries. Despite its strength, concrete does have its limits, and placing excessive amounts of weight on top of a slab can cause cracking. When you hear that a concrete mix has a strength of 2000, 3000, 4000, or more than 5000 PSI, it refers to the pounds per square inch that would be needed to crush that concrete slab.

It's natural to worry about cracks in freshly poured concrete, but some are inevitable due to the structure of the surface. Let's dive into the reasons why your fresh concrete can crack and what you can do about it. These are the most serious types of cracks you can have: when they appear in the walls of concrete blocks in your basement or other confined spaces. This is a sign of too much pressure on their walls, and that they are about to implode and fail.

If your base collapses, your entire house can collapse. Fortunately, there are solutions available. The best local foundation repair teams can provide you with easy financing to help you solve it right away. Concrete slabs may not crack if proper construction procedures are followed almost perfectly.

However, if any of the steps are not followed correctly, cracks may occur in the slab. Because many tile cracks are cosmetic, the cost often exceeds the benefit; therefore, it is common and reasonable to see minor cracks in residential concrete slabs. As concrete contracts during the curing process, vertical cracks form in the concrete or block, some so small that you can barely see them. This generally does not structurally affect the basement wall, but could allow moisture to enter if the outer wall waterproofing is not flexible enough to cover the crack.

If moisture leaks out, you might consider having a basement waterproofing contractor check the leak. Often, a concrete crack can be injected with a sealant to limit additional moisture infiltration. There are several common types of diagonal cracks in basement walls. One of the most common is when the crack starts at the top of the basement concrete wall and moves diagonally down to a corner. This is usually accompanied by an inward slope of the top of the foundation wall. It may be because the earth pushes against the basement wall and an improper connection (i.e., anchor bolts are missing) between basement wall and first floor structure.

A third type of diagonal crack appears in the corner of a window or door opening. This can be due to several causes, but one of the most common is concrete shrinkage, similar to that described in the vertical cracks section. There is no quick rule for diagonal cracks or for the foundation wall to lean inward. If you're experiencing this on your basement walls, we recommend a review. Step cracks are very similar to diagonal cracks, except that step cracks occur in cinder block basement walls and diagonal cracks occur in concrete walls.

The causes are similar to the diagonal crack problems listed above. If you see these types of problems, it's probably a good idea to have them examined by a professional so you can get an accurate diagnosis and have your foundation repairs done before any further damage occurs. A more massive vertical crack can occur when construction contractors improperly prepare concrete foundations and when the wall had poor steel reinforcement when workers poured concrete for the wall. When concrete cures (dries and hardens), it shrinks and wants to crack into relatively square sections; that's why control joints are seen on sidewalks to provide weak spots where concrete can crack without affecting aesthetics, strength, or safety. If your concrete is a little older, a concrete repair professional can help you fix the cracks. While shrinkage cracks can appear on the surface within hours of pouring concrete, it takes a full month for new concrete to fully settle. To help ensure even curing during this time period, don't let your newly poured slab dry out too quickly; instead cover it with an insulating plastic sheet or even straw to trap moisture. For example, concrete finishers can add too much water to the mix to make it more malleable.

In addition to these traditional curing methods, concrete additives and curing compounds can help concrete cure faster and resist cold. Evaluating a crack in a concrete foundation wall is often different from evaluating a crack in a concrete block or brick foundation wall. If cracks appear soon after pouring the base, it is possible that either it was mixed poorly or poured too quickly. A reputable local professional will know how best to keep a slab in good condition for optimal curing. For example, a crack in only mortar between blocks or bricks may be less concerning than one that goes through them. Once fully cured, you can also consider using a sealing compound to improve appearance and reduce cracking. Because different trucks deliver different colors of concrete and because one load was held for longer than another before pouring, lines may appear between them.