Why does concrete crack?
Concrete cracks for many reasons. Some cracks are associated with poor installation. For example, too much water in the concrete mix will reduce the strength of the concrete and cause cracks as the concrete hardens and dries. This causes shrinkage as the excess water evaporates. Concrete that is allowed to dry too fast is also at a greater risk of cracking. Failing to install control joints may also contribute to severe cracks in new concrete.
Even with perfect installation techniques, all concrete will eventually crack. Proper installation does limit this cracking, however, as the concrete is designed to crack along the control joints. When the weather is hot, the concrete will expand and push against anything in its way. When it meets an object that doesn’t give, it can crack. Freeze-thaw cycles can cause minor cracks in the surface over time. Freezing and thawing of the ground can also contribute to heaving, a process in which the ground pushes upward on the concrete slab and causes it to crack.