Characterization of fatigue damage for paving asphaltic materials*

This study investigates the fatigue characteristics of typical bituminous materials used in road applications. Fatigue testing was performed in a four‐point bending beam test apparatus under controlled strain and stress conditions. Fatigue life was defined using the classical approach as the number of cycles, N_f, to 50% reduction in the initial stiffness modulus. It has also been defined in terms of macro‐crack initiation, N₁. A different approach, based on the linear reduction in stiffness during a particular stage of a fatigue test, was introduced to define a damage parameter, and the evolution of this damage parameter with number of cycles was used to characterize fatigue life. Furthermore, refinements to the linear damage model were introduced to take into account the difference in the evolution of dissipated energy between controlled strain and stress testing modes. These modifications have enabled the identification of a unique fatigue damage rate for both controlled strain and stress test modes.