Modelling crack initiation in bituminous binders under a rotational shear fatigue load

•Crack initiation in bitumen was defined based on fatigue cracking mechanism.•An energy-based criterion was developed to predict fatigue crack initiation.•Crack initiation is dependent of modulus, surface energy, crack size and load amplitude.•Crack initiation criterion was validated and used to determine material surface energy.•Polymer modification can improve bitumen resistance to fatigue crack initiation. This study aims to model fatigue crack initiation in bituminous binders. An energy-based crack initiation criterion is developed for bitumen under a rotational shear fatigue load. Based on a damage mechanics analysis of fatigue cracking process, the crack initiation is defined and local energy redistribution around crack tips due to ‘factory-roof’ cracking is quantified. A quantitative energy criterion is proposed for the fatigue crack initiation in the bitumen using viscoelastic Griffith’s theory. The crack initiation criterion is validated through comparing the predicted and measured surface energy of the bitumen. The results show that bitumen fatigue cracking under the rotational shear fatigue load can be divided into two stages: the edge flow damage and the ‘factory-roof’ cracking. The crack initiation is dependent of the shear modulus and surface energy of bituminous binders, critical crack size, and loading amplitude. The energy-based crack initiation criterion along with the DSR fatigue tests can be potentially used to determine the material surface energy.