Experimental and numerical study of the structural and cracking behavior of an overlaid slab panel under cyclic flexural loading

This paper presents an investigation on the origin and magnitude of the internal stresses at the interface between an overlay and an underlying reinforced-concrete slab subjected to cyclic flexural loading. Internal stresses were analyzed with finite-element modeling of two configurations of reinforced-concrete slab panels measuring 3.3 × 1.0 × 0.2 m: an intact reference slab and a repaired slab with a 40-mm-thick bonded overlay. The research project included experimental testing to measure the evolution of the structural capacity and the cracking behavior of two slab panels with the same configuration and dimensions. Under laboratory cyclic loading, the overlaid slab panel showed some fine horizontal cracks progressing along the interface between the overlay and the substrate slab. The finite-element modeling revealed that the flexural crack pattern significantly impacted the stress field near the overlay interface. Flexural cracking generated stress perpendicular to the interface (normal) in the area located near the flexural crack. The magnitude of the normal stress at the interface increased with bending moment. This can produce local debonding at the overlay interface located near a flexural crack. Cyclic loading was found to promote this possible interface cracking mechanism resulting from fatigue rupture of the bond between the overlay and substrate.