Characterization of Interface Bonding in Asphalt Pavement Layers Based on Direct Shear Tests with Vertical Loading

The interface bonding condition between asphalt concrete layers is unquestioned as one of the significant factors influencing pavement performance. In order to research the interface characteristics of asphalt pavement under traffic loading, this paper presents a procedure to estimate shear strength between the asphalt layers via a direct shear test where both normal and shear stresses are applied to the interface. To do this, first, laboratory testing was conducted under varying conditions of temperature, vertical pressure, and tack coat application rate to analyze the influence of each parameter on interface shear strength. Second, the results from the tests were statistically analyzed for the significance level of each factor on interface shear strength. Finally, prediction models describing interface shear strength under the combined effect of shear and normal stresses at three different temperature levels are proposed and their feasibility is validated. All things considered, findings of this study hope to lead to a greater understanding of the monotonic behavior of interface performance in asphalt pavements. (C) 2017 American Society of Civil Engineers.