Cracks in concrete are a common occurrence and develop when the stresses in the material exceed its strength. This is usually due to the normal shrinkage of concrete as it hardens and dries. As a decorative concrete contractor, it is important to remember that these cracks are a natural part of the curing process and not caused by any fault of yours. Although there are repair options available to prevent cracks from getting worse, there is no good method to make them disappear.
It is therefore important to prepare your customers ahead of time so that they understand that cracks in concrete are extremely common and not necessarily indicative of a problem. Some types of cracks are inevitable, and the best way to control them is by properly preparing the subbase, ensuring that the concrete is not too wet, using reinforcement where necessary, and correctly placing and spacing the crack control joints and expansion joints. Narrow cracks are common in concrete slabs and generally do not indicate a structural problem. These are usually shrinkage cracks that form when the concrete cures.
However, there are times when cracks can be a warning sign of fundamental or other issues, so it is important to check other aspects of the home to determine the severity. When concrete is still in its plastic state (before hardening), it contains water. As it loses moisture during curing, it becomes smaller and can crack to relieve stress. Shrinkage cracks are common and can occur as soon as a few hours after the slab has been poured and finished.
If a crack is ¼ inch wide and in an industrial environment where heavy forklift or vehicle traffic will pass over it, it is recommended to chase the crack with a wider blade and fill it with a heavy-duty repair material. Note that a slab without steel reinforcement usually does not look as bad as one with reinforcement, but it is more prone to cracking. The best protection against structural cracking in residential structures is good compaction of soil and gravel under the slab. If a structural contractor drives a piece of heavy equipment loaded with wood on a 4-inch thick concrete slab, it can crack the green (not fully cured) concrete.
This can also happen when pouring concrete around a square column, creating four re-entrant corners. Control joints are shrink joints because they open as concrete shrinks or gets smaller. This is due to the fact that water is a certain percentage of the concrete mix, and as it dries, it has a tendency to crack. This chemical reaction, or hydration, continues for days and weeks after concrete is poured. Engineers spend their entire lives trying to get concrete slabs and walls to crack where they want.
When concrete expands, it pushes against anything that gets in its way (for example, a brick wall or adjacent slab).In conclusion, cracks in concrete are normal and often unavoidable due to shrinkage during curing. However, if you take precautions such as proper subbase preparation, reinforcement where necessary, and correctly placing and spacing control joints and expansion joints, you can minimize their occurrence.