Different approaches to depict fatigue of bituminous materials

TLDR: In this paper, the authors investigated the fatigue characteristics of typical bituminous materials used in road applications and defined the fatigue life using the classical approach as the number of cycles, N f, to 50% reduction in the initial stiffness modulus.

Abstract: This study investigates the fatigue characteristics of typical bituminous materials used in roadapplications. Fatigue testing was performed in a four-point bending beam test apparatusunder controlled strain and stress conditions. Fatigue life was defined using the classicalapproach as the number of cycles, N f , to 50% reduction in the initial stiffness modulus. It hasalso been defined in terms of macro-crack initiation, N 1 . A different approach, based on thelinear reduction in stiffness during a particular stage of a fatigue test, was introduced todefine a damage parameter and the evolution of this damage parameter with number of cycleswas used to characterise fatigue life. Furthermore, refinements to the linear damage modelwere introduced to take into account the difference in the evolution of dissipated energybetween controlled strain and stress testing modes. These modifications have enabled theidentification of a unique fatigue damage rate for both controlled strain and stress test modes.