Multi-Length-Scale Investigation of the Fatigue Behavior of Bituminous Composites: Numerical Approach

Following a comprehensive series of fatigue experiments on asphalt mixture and its subscales (mortar, mastic, and bitumen), this study utilized a 3D heterogeneous finite-element model including inclusions, matrix, and air voids to simulate bituminous composite fatigue behavior. Randomly generated particles with elastic behavior and a linear viscoelastic matrix were employed in ABAQUS. Identical shear and tension-compression loading conditions were applied to bitumen-mastic and mortar-mixture models. The damage tensor, derived from experimental fatigue equations, was generated to run models at different loading cycles. Global damage (DG) for the upper scale was computed based on the local damage of lower-scale. DG-loading cycle diagrams were generated for damage thresholds of 0.4, 0.5, 0.6, and 0.7. The fatigue life of each model was determined using experimental criteria. Simulation results revealed a maximum error of 30.8%, highlighting the significant computational time reduction in this multilength-scale modeling approach. The approach allows for determining each scale’s contribution to upper-scale damage evolution, inaccessible in the laboratory. The criteria of maximum C×N curve and FN, detailed in the companion paper (I), serve as suitable indicators for fatigue life. Both 2D optical microscopic images and numerical simulations suggest mortar as the most appropriate scale for fatigue investigation of the mixture.