Meaning
Slab edge distortion develops in concrete pavements when moisture differential creates non-uniform volume change between top and bottom surfaces. Differential moisture loss drives drying shrinkage curling, causing slab corners to lift upward away from the supporting subbase material. The action occurs because the exposed top surface dries and contracts while the sealed lower face remains moist and expanded.
Coverage applies to unbonded and jointed concrete slabs exposed to ambient humidity gradients, terminating where full depth moisture equilibrium is restored.
Moisture Gradient
Solar radiation and ambient airflow accelerate moisture evaporation from the top few centimetres of a concrete floor slab. The bottom of the slab retains ground moisture, establishing a persistent relative humidity gradient across the slab thickness. Shrinkage strain in the upper zone pulls the slab edges upward, creating an unsupported void beneath joint intersections.
Unsupported Voids
Corner lifting leaves joint edges suspended without continuous subgrade support underneath. Heavy forklift traffic crossing curled joints subjects unsupported slab edges to high flexural stresses, triggering edge cracking and joint spalling under daily wheel loads.
Remedial Grouting
Mitigating the structural impact of drying shrinkage curling involves injecting cementitious or polyurethane grout underneath lifted slab corners to restore contact with the subgrade. Slab grinding levels the raised joint lips, restoring flat surface profiles for material handling equipment.
