Shrinkage induced edge curling and debonding in slab elements reinforced with bonded overlays: Influence of fibers and SRA

An increase of infrastructures needing repair and rehabilitation has led to a growing use of bonded overlays to members such as slabs, columns, bridge decks, bridge piers, etc. These overlays are nowadays made of High Performance Concrete (HPC) able to significantly increase the structural performance with a smaller thickness.
However, HPC is generally characterized by a higher percentage of cement paste that increases shrinkage phenomena. Therefore, despite the many advantages, the performance of overlays is usually affected by debonding (from the original surface) and/or early age cracking.
In this context, results from an investigation to assess edge curling, debonding and cracking in concrete slab elements reinforced with different overlay materials are presented herein. Unlike in previous studies, actual strain measurements, carried out on the bonded overlay, were used to evaluate the shrinkage behavior. Results highlight the effect of both the rate and magnitude of shrinkage on overlay performance. The use of a shrinkage reducing admixture (SRA) was also shown to be beneficial. Furthermore, through both experimental and numerical analysis, the use of randomly distributed fibers was shown to be effective in improving overlay performance, by reducing the width of the shrinkage induced cracks.