What does the term "curling" refer to in concrete slabs?

Curling in concrete slabs specifically refers to the warping or upward curling of the slab edges or corners as it dries and undergoes temperature changes. This phenomenon typically occurs due to differences in moisture content between the top and bottom surfaces of the slab and can be exacerbated by factors such as insufficient subgrade support, temperature gradients, and the release of moisture through evaporation.

Understanding curling is crucial for concrete finishers, as it can impact the flatness and overall performance of the slab. Effective methods to reduce curling include proper curing practices, maintaining optimal moisture levels during the drying process, and carefully selecting the timing of finishing operations. This knowledge helps ensure that the finished concrete surface meets specified flatness tolerances and performs well in its intended application.