Creep and Fatigue Characteristics of Superpave Mixtures

About the report:

Laboratory creep and fatigue testing was performed on five Superpave surface hot-mix asphalt mixtures placed at the Virginia Smart Road. Differences in creep and fatigue response attributable to production and compaction methods were investigated. In addition, changes in creep response resulting from differences in specimen size were evaluated. Further, an evaluation of the effects of loading frequency, presence of rest periods, and specimen location within the pavement on fatigue life was conducted. Creep compliance values were determined using viscoelastic-based calculations, and time-temperature superposition was used to generate mastercurves. Reported creep compliance response models from the literature were found inadequate for accurately describing the creep compliance mastercurves generated during this study. Differences in creep response between specimens of different sizes were found to be due to specimen and test variability, rather than size. An evaluation of the effects of laboratory and plant production and laboratory and field compaction was inconclusive as material variability appeared greater than production or compaction variability. Simple regression models were found to be satisfactory for use in the development of prediction models for fatigue, although test data are necessary for calibration to particular mixture types. No relationships were found between fatigue model coefficients and volumetric properties of the mixtures tested because of the limited range of volumetric properties. Variability in volumetric properties between the mixtures produced at the plant and those produced to match the job mix formula did not significantly influence the predicted laboratory fatigue performance. Laboratory fatigue lives were similar between the laboratory-compacted fatigue specimens and specimens cut from the pavement; differences observed in performance were attributable to different air void contents. Predicted fatigue life was found to be statistically independent of the frequency of the applied loads or presence of rest periods for the mixtures, frequencies, and rest periods considered in this study. Minimal differences were observed between fatigue life predictions for plant-produced, field-compacted specimens cut from different locations in the pavement. This study contributes to the understanding of the factors involved in creep and fatigue performance of asphalt mixtures. The mixture responses characterized by this study are related to the rutting and fatigue performance of asphalt pavements. The choice of appropriate asphalt materials to resist rutting and fatigue deterioration will result in reduced maintenance needs and longer service lives for pavements.

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