What is the primary cause of cracking in concrete slabs?

The primary cause of cracking in concrete slabs is largely attributed to shrinkage due to drying or temperature changes. As concrete cures and hardens, it naturally loses moisture, which leads to a reduction in volume, commonly referred to as drying shrinkage. Temperature fluctuations can also cause expansion and contraction within the concrete, leading to internal stresses. When these stresses exceed the tensile strength of the concrete, cracks are likely to form.

Understanding this process is crucial for effective concrete placement and finishing techniques, as controlling moisture and temperature during the curing process is essential to minimize the risk of cracking. Proper curing methods, such as covering the surface or using curing compounds, can significantly mitigate shrinkage-related issues.

While other factors like overloading the surface or using inferior quality materials can contribute to cracking as well, shrinkage is a more consistent and pervasive issue that occurs in nearly every concrete slab as it hardens.