Mechanical characterisation of concrete-asphalt interface in bonded concrete overlays of asphalt pavements

Abstract

Bonded concrete overlay of an asphalt pavement (BCOA) is a rehabilitation technique consisting of 50–175 mm thickness concrete overlay on an existing asphalt pavement. This technique, known as thin (minimum 100 mm) or ultra-thin whitetopping (thinner than 100 mm) in the past, relies on the composite action of concrete and asphalt layers acting together with a third phase of the system being the interface between the two materials. For this study, the stiffness and strength/fatigue resistance of this interface have been characterised by means of a series of laboratory tests conducted on asphalt and composite cylindrical specimens under different loading and environmental conditions. Testing conditions included wet and dry, and temperatures between 5 and 40 °C, a range applicable to BCOA asphalt bases in California. Experimental results from this study indicate the mechanical nature of the concrete–asphalt interface is strongly related to that of the asphalt. The interface stiffness showed clear time dependency, and it significantly softened under wet conditions. Experimental results from this study are in line with common belief that water is one of the critical factors leading to failure of BCOA sections, but do not support the common belief that concrete does not bond well to new asphalt.

Keywords:

• Bonded concrete overlay
• asphalt pavement
• rehabilitation
• concrete–asphalt bonding

Acknowledgements

Results here presented constitute the preliminary laboratory testing of a three-year research project focused on BCOA performance. The research presented in this paper was requested and sponsored by the California Department of Transportation (Caltrans). Caltrans sponsorship of that work is gratefully acknowledged. Special thanks are for Nick Burmas, Joe Holland, and Deepak Maskey for their support for and contributions to this research project. The contents of this paper reflect the views of the authors and do not necessarily reflect the official views or policies of the State of California, or the Federal Highway Administration.