LAUSR

Abstract This study aims to determine the endurance limit and macro-cracking threshold of a viscoelastic composite material using a fracture mechanics approach. Asphalt mixtures containing different recycled material contents and recycling agent doses were fabricated and long-term oven aged. Dynamic modulus tests were first conducted to obtain viscoelastic properties including complex modulus and phase angle, and then damage properties were determined from monotonic semi-circular bending tests. Pseudo displacement was calculated to remove the viscous effect from the total dissipated energy, and the energy balance approach and Griffith crack growth criterion were modified and used to predict the bond energy with the aid of discrete element modeling. With the bond energy computed, the endurance limit was determined to be frequency and mixture composition dependent. The macro-cracking threshold defined as the boundary between healable micro-cracks and non-healable macro-cracks was also identified to be frequency and composition dependent using a damage density concept. Both the endurance limit and the macro-cracking threshold were utilized in the asphalt mixture Black Space diagram, which is capable of illustrating the effects of aging, recycled materials content and recycling agent dose in asphalt mixture composites for the prediction of fracture performance.