Why do concrete slabs curl or warp?

Concrete slabs curl due to the effects of temperature variation between opposing surfaces of the slab. Concrete slabs may curl when the top surface of the slab is cooler than the bottom surface. The cool surface shortens due to thermal shrinkage, which may deform the perimeter of the slab section upward as the temperature of the bottom surface of the slab stays at a higher temperature. On the other hand, the top surface will expand when it is heated (such as with intense sunlight), which may relax curling or cause reverse curling. Reverse curling is when the concrete slab deforms downward instead of upward.

Concrete slabs warp due the effects of moisture variation between opposing surfaces of the slab. As the top surface of the slab dries, the volume change causes the surface to shorten while the bottom of the slab stays moist. Because the bottom surface stays moist, there is little or no shortening due to the effects of drying. Again as the top surface of the slab shortens and the bottom surface does not the edges lift.

Concrete Hydration
UltraCure wet curing blankets have UltraCure NCF for slab on grade applicationsnumerous advantages in preventing slab curling and warping. First is has deep hydration capability. When properly installed, the UltraCure blanket provides a fully saturated surface, helping the concrete to achieve more complete hydration at the surface than other products. Unlike other single-use blankets which tend to dry out after 3-4 days, UltraCure NCF (Natural Cellulose Fabric) provides constant hydration and maintains a 100% relative humidity condition on the slab for the entire 7-day curing period (with proper installation).

Secondly, this wet curing blanket feature non-staining, super absorbent fibers that effectively trap water and serve as a hydrating reservoir for the slab as it cures, reducing moisture loss at the surface which can lead to curling.

UltraCure NCF also features a semi-transparent white poly backing, which provides constant visual reinforcement that the slab remains wet for the entire curing period. The poly backing retards evaporation from heat and wind, both of which can lead to curling at the edges of the slab.

Lastly, the superior water retention ability of UltraCure NCF allows the blanket to absorb more than 46 gallons of curing water per 1,600 sq. ft. roll, providing the critical moisture required for the long term wet curing of concrete surfaces. With typical application and proper installation, the superior absorbency demonstrated by UltraCure NCF means there's no need to re-wet the slab. UltraCure NCF is designed to stay wet, lay flat and reduce moisture loss.

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