Study of Interlayer Shear Effects in the Structure of Asphalt Overlay on Existing Rigid Airfield Pavement Using the Digital Image Correlation Method

Shearing would occur in the interface of asphalt overlay on existing rigid airport pavements due to the differences in the mechanical properties of the materials loaded by aircraft. The interlayer contact affects the mechanical characteristics of the asphalt overlay directly. Nevertheless, effective interlayer relative displacement obtained accurately by the existing displacement sensors of the loading apparatus remains challenging. This study aimed to use digital image correlation technology to obtain effective interlayer relative displacements and enhance the accuracy of interfacial contact parameters. Composite structure specimens were prepared, and the fixture for interlayer shear tests was designed and fabricated. Then, the digital image recognition scheme for the required markers was designed and optimized. The effective interlayer relative displacement values were obtained by image recognition and calculation of surface markers on the specimens. Finite-element simulations validated the mechanical response of the composite specimens with interlayer shearing. The results indicated that the optimized marking approach using the wall mending agent for surface application and color coding enhanced the image recognition quality of marking points on the specimen surface. Further image extraction provided effective interlayer relative displacement values in interlayer shear, thereby improving the accuracy of the interface contact parameters. For the composite structure specimens utilizing styrene-butadiene-styrene (SBS) modified asphalt as the tack coat, the corresponding maximum interlayer shear stress strength was 0.6 MPa, and the fracture energy was 2,917 J/m2. This research provides valuable insights for investigating the impact of interlayer contact in composite pavement structures on the mechanical characteristics of asphalt overlay.