Modelling effects of aging on asphalt binder fatigue using complex modulus and the LAS test

The linear amplitude sweep (LAS) test is considered a useful tool for evaluating fatigue of asphalt binders. It has been confirmed that a good correlation exists between fatigue performance of binders and mixtures in a few studies. While the change in binder fatigue with load or strain level is well studied and modeled, the effects of oxidative aging remain difficult to explain or to model in a simple format. In this paper, the combined effects of strain and aging are investigated and a method for estimating binder fatigue behavior after different aging durations from limited measurements is introduced. LAS tests were conducted on eight binders at three different aging periods in the PAV. It is found that binder fatigue damage parameters C-1 and C-2 have a good linear relationship with aging level when using the dissipated pseudo-strain energy approach. The results also show that LAS parameters A and B at different aging duration maintain a linear relationship with the binder complex modulus (G*) measured at corresponding aging conditions. Therefore, a new fatigue life (Nf) model accounting for strain level and aging effect is proposed using a power function of the binder G*. To verify the model, its parameters are fitted using test data at first two aging conditions and used to extrapolate and predict the fatigue life at extended aging conditions. This study findings offer a simpler and reliable method to predicted values of fatigue life at new aging condition using both 35% damage level and maximum stress failure criteria that are recommended in AASHTO TP101-12 and AASHTO TP101-14, respectively. The new model will allow use of the LAS procedure to a wider range of aging and strain level conditions for which binders could be subjected to in the pavement.