Abstract
A mechanically consistent isothermal density-driven framework is presented to model fatigue damage in asphalt mixtures using an energy-based extension of density-driven damage mechanics (D 3 M). The formulation embeds an energy-controlled density degradation expression within a scalar-modulus viscoelastic skeleton and couples it with a finite-strain (compressible Neo-Hookean) stress description for cyclic tension. The viscoelastic skeleton is calibrated from AMPT dynamic modulus and phase angle data per AASHTO TP 79 through reduced-frequency master curves and identification of a temperature-dependent relaxed modulus. The D3M degradation relation is calibrated from AMPT direct tension cyclic fatigue tests per AASHTO TP 107 at 20 °C and 10 Hz, using three replicate specimens per condition (n = 3). Cumulative dissipated energy is adopted as the damage-driving internal variable, enabling cycle-by-cycle inference of density ratio evolution and the associated reduction of the damaged relaxed modulus. The calibrated framework reproduces the observed evolution of cyclic stress amplitudes over most of fatigue life and captures mixture-dependent fatigue trends, while remaining compatible with standard AMPT characterization protocols.