Experimental study of asphalt mixture interlayer interface shear damage based on piezoelectric active sensing methodology

Interlayer adhesion failure in asphalt mixtures accelerates structural deterioration, yet quantifying progressive damage remains challenging. This study proposes an integrated evaluation using damage extent (Dc) and ultrasonic-derived damage index (DI) from signal energy attenuation. Shear-compression tests with stepwise ultrasonic measurements (20–160 kHz) were performed on two-layer specimens (AC-13 over AC-20). Damage progression was monitored via digital image correlation and wavelet packet energy analysis. Results show DI evolves consistently with Dc, reflecting crack propagation. Shear strength peaked at 1.58 MPa under 8 mm displacement, with DI sensitivity thresholds of 0.89 (60 kHz) and 0.95 (140 kHz), and Dc reached 2.14%. Effective crack detection requires excitation above 60 kHz and below 160 kHz due to viscoelastic constraints. DI serves as a damage-sensitive indicator for interlayer cracking under laboratory conditions, supporting future embedded monitoring systems.