Insight into the critical evaluation indicators for fatigue performance recovery of rejuvenated bitumen under different rejuvenation conditions

This study aims to propose critical fatigue indicators for evaluating the restoration effectiveness of various rejuvenators on the fatigue performance of aged bitumen. The influence factors of rejuvenator type/dosage and aging degree of bitumen are involved, and different fatigue parameters from linear viscoelastic (LVE), linear amplitude sweep (LAS), and time sweep (TS) tests are analysed. The results reveal that bio-oil exhibits the greatest rejuvenation efficiency in improving fatigue life of aged bitumen, followed by engine-oil and naphthenic-oil rejuvenators, while aromatic-oil shows the lowest effect. Moreover, the rejuvenation percentages on fatigue parameters of rejuvenated bitumen enhance significantly with increased rejuvenator dosage but weaken as the aging level deepens. The fatigue failure temperature (FFT) from the LVE test, fatigue life (Nf5), peak strain (ɛsr), elastic modulus (E) from the LAS test, and crack width (C500) from the TS test are recommended as critical indicators for fatigue performance evaluation of rejuvenated binders. Further, the crack width greatly correlates with other essential indicators and can be predicted using correlation equations without conducting the time-consuming time sweep test. The difference in these critical fatigue parameters of various rejuvenator-aged bitumen blends provides the macroscale basis for future nanoscale mechanism exploration and superior rejuvenator development.