Effect of Aging in Fatigue Behavior of Asphalt Binder, Mastic, and Mixture

The aging of asphalt binders from exposure to environmental conditions significantly affects the final performance of the asphalt mixture that is layered in the pavement. This effect on the fatigue behavior of the mixture and its sensitivity to temperature changes is highly significant. Evaluating these properties on mixtures using the procedures described in the UNE EN standard could be very time consuming. This document presents the efforts carried out to evaluate the effect of aging on the fatigue behavior of three binders, mastics and mixtures at different temperatures (+10, +3 and -5oC). A strain sweep test that allows fatigue related parameters for these materials to be obtained in a short testing time was employed. Results have shown that the polymer modified binder (PMB) provides the best fatigue results, even though the characterization parameters, penetration and softening point temperature suggested that it was the most damaged by the aging procedures. In general aging increases the stiffness of asphalt materials. The PMB obtained the best results at all temperatures and aging stages; however, the differences noticed at -5oC were very small. A new concept called Equivalent Layer Thickness (ELT), which is used to quantify the loss of fatigue resistance of mixtures, has been developed. The PMB mixture obtained the best ELT values in all cases; but as previously mentioned the differences at low temperatures were minimal. The authors suggest that even though PMBs produce the best fatigue resistant asphalt materials, their performance at low temperatures when aged should be improved.