Q.: Are there any standards for an acceptable amount of curling for a concrete floor slab?

A.: We know of no standards. The acceptable amount of curling will be related to the use of the floor and the requirements of the floor-covering installer if the floor will be covered. For uncovered industrial floors exposed to traffic from heavy forklifts, curling may cause the floor slab to crack near the joint where the curling occurs. Lighter loads might cause little or no cracking, and cracking may be acceptable if it doesn't cause spalling at the crack location.

If the floor will be covered with tile, wood flooring, or a material that reflects surface discontinuities, as little as 1/8 inch of curl may be objectionable. If this is the case, the designer should plan to reduce curling by reducing concrete shrinkage and perhaps reinforcing the floor with more than just temperature steel.