Creep Compliance: A Parameter to Predict Rut Performance of Asphalt Binders and Mixtures

Abstract

Highway agencies have been using polymers in asphalt binders to reduce rutting-associated distresses in asphalt pavements. Rheological parameters like complex shear modulus (G*) and phase angle (δ) in the form of G*/Sinδ were used to predict rut resistance of asphalt binders, which have been replaced by a new parameter called non-recoverable creep compliance. The present study investigates the creep compliance of straight run (neat) and polymer-modified asphalt binders, at their high performance grade temperature (58, 64, 70, and 76 °C), using a multi-stress creep recovery test. The test data are used to assess the temperature and stress sensitivity of asphalt binders at different percentages of polymer. Asphalt mixtures, prepared using four asphalt binders, are tested in a wheel tracker to arrive at a relationship between creep compliance and rut resistance of asphalt mixtures. This study has revealed that creep compliance depicts the temperature and stress sensitivity of asphalt binders and asphalt binders’ polymer modification. Based on the stress sensitivity and creep compliance data, the suitability of asphalt binders for different traffic loadings is suggested. The present study proposes a reasonable relationship between creep compliance at 3.2 kPa and rut depth of asphalt mixtures, obtained from a wheel tracker test. This laboratory study may be extended in the future for field validation and development of asphalt mixtures performance-related specifications.