Most cracks occur within 2-3 days of concrete placement. Cracks in a concrete garage floor may indicate foundation or other problems. As buyers or homeowners, we want to know how to tell if these cracks are serious, or basically when to be concerned. The good news is that most cracks in garage floors are common and are not an indication of serious structural problems, however, there are some that indicate that maintenance is needed or that there may be a structural concern.
Although concrete is a very strong building material, it has its limits. Placing an excessive amount of weight on a concrete slab can cause cracks. When you hear that a concrete mix has a strength of 2000, 3000, 4000 or 5000 PSI, it refers to the pounds per square inch it would take to crush that concrete slab. If you are a decorative concrete contractor, always remember that you have done nothing to cause the cracks.
They are a natural part of concrete curing and hardening. There are very good repair options to prevent cracks from getting worse, but there is no good method to make them go away. When it comes to how to handle cracks in concrete, preparing your client in advance will work best for you. Plastic shrinkage cracks Probably the most common reason for early cracks in concrete is plastic shrinkage.
When concrete is still in its plastic state (before hardening), it is full of water. This water takes up space and makes the slab a certain size. As the slab loses moisture during curing, it becomes slightly smaller. As concrete is a very stiff material, this shrinkage creates stresses in the concrete slab.
As the concrete shrinks, it is dragged along its granular sub-base. This impediment to its free movement creates a stress that can literally pull the slab apart. When the stress is too great for the hardened concrete, the slab cracks to relieve the stress. Especially in hot climates, shrinkage cracks can appear as soon as a few hours after the slab has been poured and finished.
Crazing is the development of random fine cracks on the surface of the concrete caused by shrinkage of the surface layer. Carbonation occurs when carbon dioxide from the air enters the concrete and reacts with hydroxides, such as calcium hydroxide, to form calcium carbonates in the presence of water. One of the most common mistakes people make when looking at their garage floor is mistaking a cold joint for concrete that has actually cracked. Typical areas where alkali-silica reaction (ASR) occurs are concrete structures, such as piers and bridges, that are near the waterline or in a body of water.
Once a qualified and licensed inspector has diagnosed the cause and significance of concrete cracking, it is important that accurate repair methods are followed. Understand what your contractor is doing with respect to each of the items listed above and you will get a good concrete job. Cracks that are identified as small and hairline (less than 0.3 mm wide) are generally considered acceptable as part of a minor slump, depending on the purpose and intent of the concrete structure, the environment in which it is placed, service life design and durability design. In some cases, this wire mesh does not end up in the central area, but remains in the subgrade with the freshly poured concrete on top of it, and therefore does not perform as it is designed to perform.
Although early cracking may initially be considered a minor deficiency, it is advised that building owners and those responsible for maintenance appoint qualified repair contractors to properly repair these cracks as soon as possible to help prolong the life of concrete structures. Control joints are pre-planned and pre-installed to prevent the concrete from cracking due to shrinkage during curing. The product reacts quickly with water, chasing the water present in the crack and begins to foam and expand, filling the entire crack, resulting in a strong bond with the concrete and a flexible waterproof seal that prevents future water leakage. Often metal mesh is used as reinforcement, which holds the concrete pieces together but does not prevent cracks.
This will allow cracks to occur, because the concrete is shrinking around all this mesh, and the mesh may not shrink with it. So if the concrete is poured in the colder months, assuming it is placed on a good foundation, it will have fewer and smaller cracks. If a house is on a hillside and there is a living area or open space under the concrete garage floor, then all cracks should be assessed for safety reasons. Cracks in concrete are common and occur when stresses in the concrete exceed its strength.