Summary: The key to a successful BCOA is to maintain the concrete-asphalt bond. When the bond is effective, the neutral axis of the overlay is shifted lower resulting in smaller tensile stress in the concrete and thereby allowing the thin overlay to carry large amounts of traffic. However, the bond degrades due to fatigue and the loss of the bond results in premature failure of the BCOA. Because of the lack of understanding of the interface debonding mechanism, the current BCOA design procedures still employ constant adjustment factors developed based on limited projects to account for the increase in the overlay stress due to partial bonding. The use of such empirical constants can lead to very unreliable design. Therefore, a quantitative framework that can predict the growth of interface debonding as a function of the fatigue loading is a key to improving the current design procedures.