Laboratory and Numerical Investigation of Interface Debonding of Bonded Concrete Overlay of Asphalt and Its Effect on the Critical Stress in the Overlay

摘要

Bonded concrete overlay of asphalt (BCOA) is a viable technique for rehabilitating distressed asphalt pavements by bounding a Portland cement concrete overlay to the asphalt pavement. BCOAs are more durable solutions especially for highways and major city intersections where the constant maintenance using bituminous materials is not desirable. They also have advantages over the unbonded concrete overlays in terms of lower cost and lesser concern of the overhead clearance. As a result, BCOA has gained increasing popularity over the past two decades. Up to 2010, over 300 projects have been recorded in more than 35 states, totaling over 7.5 million m2.udThe 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 to 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 might lead to very unreliable design. Therefore, a quantitative framework that can predict the growth of interface debonding as a function of the fatigue loading could be a key to improving the current design procedures.udA fracture mechanics based framework has been developed to determine the growth of debonding area as a function of the number of fatigue loads and the fracture energy subjected by each individual load. Wedge splitting tests were first performed to understand the interface fracture and investigate the debonding resistance of the interface under Mode I loading. Accelerated loading tests were then conducted on BCOA slabs to simulate the fatigue of the interface bond. In addition, a transient-wave based nondestructive method was developed to detect the growth of the interface debonding and a cohesive zone model was established to calculate the fracture energy.