The primary objective of this research is to develop a comprehensive guideline to minimize the debonding distress in asphalt pavements. A particular focus of the study is the distribution and dissipation of shear stresses under traffic loading and ways that such stress affects the interlayer bonding. The systematic and mechanistic framework developed in this study includes a computational analysis methodology that is used to determine the critical stress and strain states in layered asphalt pavements under moving vehicle loads using a computational analysis program. Moreover, the comprehensive framework includes the following: a direct shear test protocol that can be used in the laboratory to evaluate the shear bond strength between the asphalt layers, a shear strength database for different tack coat materials at various confining pressures, temperatures, and loading rates, a mechanistic prediction model for shear strength, and descriptions of the effects of various pavement and environmental factors on the debonding distress. A particular focus of this study is to evaluate the distribution of stresses and strains under traffic loading using a computational pavement analysis program in order to investigate the ways that such stresses and strains affect interlayer debonding. Then, these states of stress and strain determined from the computational analysis of the asphalt pavement section are reflected in a test protocol that can be used to evaluate the interface shear bond strength in the laboratory, especially in terms of the selection of the appropriate level of normal confining stress for the shear strength test.
The time-temperature superposition (t-TS) principle is verified for the interface shear bond strength and interlayer shear stiffness that have been evaluated using the developed test protocol. Once the t-TS principle for interface shear bond strength is proven to be completely valid for specimens with different tack coat materials at the layer interface, shear strength mastercurves are constructed. Also, a procedure for the development of an interface shear strength model equation from the shear strength data sets obtained at different temperatures, loading rates, and normal confining stresses through the interface shear bond strength tests is described.
This research presents the concept of maximum shear ratio (MSR) as a means of determining the debonding potential of asphalt pavement. The MSR was defined as the maximum value of the shear ratio, i.e., the shear ratio at a given location at the layer interface, which is the ratio between the shear stress at that location and the shear bond strength determined for the shear strain rate and normal confining stress at that location. In this study, the MSR concept is coupled with the shear bond strength predictive model in order to propose a mechanistic framework to determine the debonding potential of asphalt pavement.
