Answer to: What is Concrete Curling in Slabs?
Curling is the distortion of a slab into a curved shape by upward or downward bending of the edges. This distortion can lift the edges of the slab from the base leaving an unsupported edge or corner which can crack when heavy loads are applied. In other cases, slabs may curl over an extended period.
The upward or downward movement of a concrete slab’s corners or edges due to moisture and/or temperature differentials within the concrete is known as ‘curling’ or ‘warping’. It may be evident in concrete elements other than slabs, eg wall panels. This Data Sheet is concerned only with curling in slabs, and particularly slabs on ground.
Curling typically occurs some months after concrete placement but can occur much earlier. The extent of movement is usually minimal (up to only a few millimeters) but may in severe cases be as much as 20–25 mm. In the worst cases, slab edges and corners may lift off the ground and stepping between adjacent panels may occur. The areas typically affected are those from 600 to 1500 mm from the free edges of the slab.