ABSTRACT
In bonded concrete overlays, the evaporation and diffusion process inside the repair concrete result in a non-uniform moisture gradient near the surface (Carlson, 1937) and induce a shrinkage gradient through the repaired layer (Bazant 1989, Weiss 1999 & Moon et al., 2004, 2006). In these cases, restraint from the surrounding structure prohibits the concrete from moving freely and tensile stresses are set up in the repair layer together with shear and peeling stresses at the interface (Rahman et al., 2000). If the tensile stress exceeds the tensile strength of the repair material and/or the stresses at the interface exceed the bond strength, cracking and/or delamination will occur in the patch repair. This phenomenon is more critical in high-strength repair concretes with low water to cement ratios (Shin & Lange 2004) which usually show high shrinkage values in the same conditions.
