Effects of Asphalt Mixture Properties on Permanent Deformation Response

The hot-mix asphalt (HMA) rutting prediction model in the Mechanistic-Empirical Pavement Design Guide (MEPDG) uses a relationship that includes the effects of mix characteristics only through the resilient strain, which in turn is a function of the dynamic modulus (|E^*|) of the mix. However, increasing evidence suggests that the use of |E^*| alone may be insufficient to characterize completely the permanent deformation behavior of HMA. In addition to effects already considered by the MEPDG model with |E^*|, the effects of mix characteristics on permanent deformation are analyzed with the use of the results of repetitive axial permanent deformation tests from laboratory-compacted HMA specimens. Results of multiple linear regression analysis indicate that binder type, effective binder content, and air void content have significant effects on model parameters for permanent deformation. The potential effects of mix characteristics on these parameters are analyzed with the use of the MEPDG model and an HMA pavement section with four levels of compaction. Scenarios in which the mixture characteristics are incorporated solely by means of |E^*| are compared with scenarios in which the effects of air void content and asphalt content are incorporated into the rutting prediction model by adjusting its parameters according to relationships established in the laboratory. Empirical laboratory evidence supports the hypotheses that, regardless of mixture properties, universal values for permanent deformation model parameters do not fully account for mixture-specific contributions to rutting and that other mix characteristics (e.g., air void content) may be needed to supplement |E^*| for the appropriate characterization of the permanent deformation of asphalt mixtures.