Curling Of Concrete Floor Slabs

When curling in a concrete slab application cannot be tolerated alternate options include the use of shrinkage reducing admixtures shrinkage compensating concrete post tensioned slab construction and vacuum dewatering.

Curling of concrete floor slabs.

It may be evident in concrete elements other than slabs eg wall panels. Achieving such surfaces in floor slabs however is quite difficult because of the moisture and temperature gradients that cause them to curl at the joints. The moisture loss occurs in all envi ronments at less than 100 relative humidity and is typically more severe in areas of low relative humidity. Certain types of breathable sealers or coatings on slabs can work to minimize moisture differentials and reduce curling.

Curling is the distortion of a slab into a curved shape by upward or downward bending of the edges. The effect of curling on floor serviceability varies depending on the intended use. If the total curl is less than 1 4 inch or curling occurs primarily in low traffic areas or under storage racks the owner can often live with it provided that cracking isn t excessive. Such curling seriously affects the operation of an industrial facility.

Founded in 1904 and headquartered in farmington hills michigan usa the american concrete institute is a leading authority and resource worldwide for the development dissemination and adoption of its consensus based standards technical resources educational programs and proven expertise for individuals and organizations involved in concrete design. This data sheet is concerned only with curling in slabs and particularly slabs on ground. Floors subjected to heavily loaded forklift traffic may rapidly deteriorate causing safety problems. When concrete slabs on grade curl the curling sometimes has little effect on floor performance.

The american concrete institute. Curling is a phenomenon that occurs in concrete slabs lifting the edges of them and causes problems such as. Placing 4 bars on 18 inch centers both ways and chairing the bars to keep them within an inch of the surface has been suggested see controlling curling and cracking in floors to receive coverings concrete construction july 1998 pp. The occurrence is primarily due to differences in moisture and or temperature between the top and bottom surfaces of a concrete slab.

This curling effect can lift the edges or the middle of the slab leaving an unsupported portion of the concrete which can then crack and break when weight is applied. Reinforcing steel placed near the top surface of the slab can help restrain curling. It is caused primarily by loss of moisture from the concrete surface as the con crete dries. 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.

Breaks of the slabs when applying loads on the edges which are literally flown on the base of the pavement. There are occasions however when curling isn t tolerable and repairs are needed.