Multiscale fatigue model for bituminous mixtures

Fatigue failure is one of the main failure mechanisms in flexible pavements, resulting in the decrease of material stiffness due to repeated (traffic) loading, mainly driven by the propagation of microcracks. In this work, a new fatigue model for bituminous mixtures is proposed, which combines multiscale modeling (continuum micromechanics) with fracture mechanics. This model is validated by means of stress-controlled cyclic uniaxial tensile tests. The respective experimental data are obtained at different temperatures, considering different loading amplitudes and frequencies. For these conditions, the fatigue behavior, characterized by a decrease of the complex modulus and an increase of the phase angle with increasing number of load cycles, is well described by the proposed model. The multiscale nature of the proposed model allows determination of the influence of the mix-design, the material behavior of each constituent, and the type of loading on the overall fatigue performance. Finally, performance-based optimization of bituminous mixtures with respect to their fatigue behavior becomes possible.