Effects of interlayer surface characteristics on the interface bonding between double-layered asphalt systems

This study aims at comparing the surface characteristics of the interface between double-layered asphalt specimens composed of conventional or rubberised asphalt concrete mixtures. To this end, first, the double-layered asphalt specimens with a novel interlayer isolation film (IIF) in between were manufactured, and then the asphalt specimens were non-destructively separated at the layer interface. Subsequently, an ultra-high-resolution three-dimensional (3D) laser scanner was utilised to acquire the respective 3D point cloud data. Next, the 3D morphology of the interface between asphalt layers was reconstructed using image processing techniques, and the corresponding surface characteristics were determined accordingly. In this respect, three indicators of impact ratio (IR), degree of curvature (DC), and curvature ratio (CR), which are dependent together and developed in a successive approach, were developed respectively to quantitatively describe interlayer surface characteristics of adjacent layers. Subsequently, the relationship between the interface shear strength and interface characteristics of double-layered specimens was compared and analyzed. The results showed that the CR could effectively reflect the surface characteristics of the interface between double-layered asphalt specimens. Finally, the statistical analysis revealed that the interlayer surface characteristics (CR) statistically had a significant effect on the interface shear strength.