Modelling and characterising the fatigue behaviour of asphaltic concrete mixtures

This paper investigates the fatigue behaviour of asphaltic concrete mixtures subjected to Indirect Tensile Fatigue Test (ITFT) under a stress-controlled mode. The conventional stress/strain based approach is used to determine the number of cycles to failure and initial strain value under specified repeated load levels. The fatigue test results indicate that the MS-2 mix (containing 60% and 40% of coarser and finer particles, respectively) prepared with the 40/50 penetration grade binder accumulates less initial strain, and has a relatively better resistance to fatigue than the other tested mixtures. Furthermore, this fatigue behaviour is modelled using a power, intrinsically linear, and non-linear functional specifications. Among these, a non-linear model formulation is found to be the best suited, expressing the number of cycles to fatigue failure as a function of the initial strain, the viscosity, the optimum bitumen content, and the resilient modulus. The fatigue model captures high variability in the data (R2 = 0.86) with a reasonable prediction error (of 15%) as compared to other models. The findings of this study can serve as the basis for selection of asphaltic concrete mixtures based upon the fatigue life criterion; the models proposed in this study can be used as a precursor to determining the fatigue behaviour without performing laborious laboratory testing.