Continue reading to learn some common, and overlooked, causes behind concrete cracks, and some methods that professional pavers use to prevent excessive cracking in concrete.
Cracks in Concrete
A professional paving team will use special tools and strategies to stop concrete from cracking excessively. This includes proper sub-grade preparation, accurate water-to-material mix ratio, and fashioning reinforcement in the proper places. For this reason, it is vital to choose an experienced and reputable concrete repair service that can provide quality results you can trust. But keep in mind that concrete cracks can happen despite of everything else. Here are some reasons why:
ShrinkageOne of the most common reasons for cracks to appear in newly-paved concrete is plastic shrinkage. When concrete is still soft, and not yet hardened, it is in its plastic state. This is when the concrete is still full of water. And since water takes up space, it makes the concrete slab a certain size and shape. But as the concrete cures, and leaves its plastic state, the water inside begins to evaporate. This can cause the concrete to slightly shrink.
Concrete is rigid, so the shrinkage causes a lot of stress on the concrete slab. As it moves along the granular sub-grade, it can cause the slabs to move apart from each other. And when the stress gets to be too much, cracks will appear to relieve tension. All of this is exaggerated in hotter climates and weather.
When installed properly, these inevitable cracks are hairline fissures, and barely visible. But if the installation and mixing process is done inadequately, the cracks will be larger and more abundant. One example is mixing the concrete improperly by making it too wet. It is important to get the right water-to-mix ratio to ensure less cracking. It is common for under-qualified pavers to mix concrete with more water because it is easier to install and finish, especially in hot temperatures. Although a few extra gallons won’t have much effect, too much water can create weaker pavement and larger cracks.
When concrete is exposed to hot weather, it expands as it increases in temperature. Cracking occurs when the concrete slab expands to an obstruction point that it cannot pass, such as a curb, brick wall, or even another concrete slab. Professional pavers know to use expansion joints to help control the amount of cracking in concrete. An expansion joint is simply a point of separation between two static surfaces. Also called isolation joints, these points of separation are filled with a type of compressible material that provides adequate shock absorption. This allows a little room for concrete to expand, thus reducing the amount of cracking.
Heaving is another common cause behind concrete cracks. It occurs when concrete slabs, like sidewalks, experience a series of freeze/thaw cycles. The repetition of frozen and thawed states causes concrete to shrink and expand multiple times. This results in the ground beneath concrete to lift, causing the slab to heave or bow. Slabs can rise several inches, and also be affected by large tree roots.
Drains, sewer covers, and other rounded objects in concrete pavement are common causes for cracks. In the same way that concrete experiences expansion and shrinkage, round objects inhibit concrete from compressing, thus resulting in excessive stress on the slab. This creates cracks in the concrete.
Professional pavers will constructively incorporate control joints concrete slabs. These are contraction joints that give concrete a designated place to crack when shrinkage or expansion occurs. Instead of cracking randomly through the slab, the concrete will crack exactly on the control joints.