Abstract
This study aims to assess the residual mechanical properties of asphalt concrete (AC) using ultrasonic pulse velocity tests with P- and S-waves on field-extracted plates. In order to evaluate the impact of traffic load on the residual mechanical properties, the plates are extracted from both trafficked and untrafficked areas. S-wave measurements were particularly challenging because of high attenuation of the material, addressed by using piezoelectric transducers operating in shear mode and advanced signal processing. Three methods for the time of flight determination are proposed, taking into account the signal-to-noise ratio effects. The C-scan measurements are presented in the form of spatial cartographies, followed by statistical analysis to assess the homogeneity of the plates across the spatial distribution. The ageing and heavy vehicle traffic degrade the material’s residual mechanical properties, leading to reduced wave velocities, particularly in the base layer’s materials. Comparing with traditional two-point bending test the high-frequency dynamic modulus calculated from US measurements matched well with traditional complex modulus test results and viscoelastic rheological modeling. Ultrasonic pulse velocity measurements indicate that aged AC can be considered as an orthotropic material with transverse isotropy.