Influence of interface bond on the performance of bonded concrete overlays on asphalt pavements

Bonded concrete overlays on asphalt pavement (BCOA) offer a rehabilitation method for moderately distressed asphalt pavements. A performance review of the BCOA projects constructed in different parts of the United States suggests that the main distresses, such as longitudinal and corner cracks, develop primarily as a result of debonding of the asphalt layer from the concrete overlay. Debonding, which reduces the contribution from the underlying asphalt layer, increases the stress in the concrete layer, leading to the development of cracks. In this study, a finite-element analysis was performed to investigate the influence of the interface bond on the load-induced stress for 76-mm (3-in.), 102-mm (4-in.), and 152-mm (6-in.) concrete overlays. It was found that debonding can increase the magnitude of the load-induced stress in the concrete by up to 40-55%. Maintaining high joint load transfer efficiency (LTE) reduces the tensile stress at the interface that contributes to debonding. Relationships were developed between LTE and debonding stress for a range of overlay designs. The findings from this study can be used to facilitate the integration of debonding models in the mechanistic-empirical design procedure for BCOA. The results from this investigation can also be used in establishing a reasonable range of the target values for interface bond strength needed when constructing BCOA to ensure good performance.