Curling of Concrete Slabs
Diagnosis: Also referred to as edge-curling, it’s the lifting of a slab or topping at its corners and/or edges. You’ll see cracks or deterioration around the perimeter edge, and a noticeable up-lift at perimeter edge when checked with a straightedge.
Cause: Dimensional differences between the slab surface and sub-surface caused by shrinkage. The side that faces the sun dries first and shrinks while the other side stays wet and does not. The resulting tension causes the concrete to curl, or warp similar to a wet board in the sun.
Possible concrete repairs:
Structural: In some situation, strategic cutting alone can relieve the tension and grouting to restore continuity can follow. Severe curling will require cutting and demolition to remove compromised slab edges. This may be full or partial depth. In the case of a curling at a joint, the repair should include the isolation or re-cutting of the joint.
The material of preference for this type of repair is often a resinous type epoxy, methacrylate or other material for bond and tensile strength as well as the “ductility” these products possess for impact resistance. Some repair materials even incorporate steel aggregate particles to resist impact and thermal shock. Experienced repair contractors will often anchor this type of patch along the edge with concrete nails. This repair assembly is sometimes referred to as an “armored joint.”
Aesthetic: Clean and chip any loose material, grout joint, cracks and any voids. Plane or grind down lifted area until flush. This is usually a fairly serious repair, often in heavily trafficked areas. Aesthetics are not often of as much importance. But if they are, shot-blast the slab and apply a pigmented coating.