A comparative study of temperature shifting techniques for construction of relaxation modulus master curve of asphalt mixes

Several temperature shifting techniques have been proposed for construction of relaxation modulus master curve of asphalt mixes using the time–temperature superposition principal; however, it is not clear which one works better than the others. Therefore, the main objective of this study was to compare the relative ability of five common temperature shifting techniques, i.e. Numerical, Log-Linear, Williams-Landel-Ferry (WLF), Modified Kaelble, and Arrhenius, to construct the relaxation modulus master curve for dense graded asphalt mixtures. For this purpose, 72 cylindrical asphalt mixture specimens containing crushed stone aggregates with 60/70 penetration asphalt binder were fabricated using two different aggregate gradations, two binder contents, two air void levels, and three aging conditions with three replicates for each experimental combination. Direct tension relaxation modulus tests were conducted on the specimens at four different temperatures using the trapezoidal loading pattern at a low level of strain. The tensile relaxation modulus master curves of all the specimens were constructed using the Generalized Logistic Sigmoidal Model for the five shifting techniques. Finally, both the graphical and statistical comparisons were made among the temperature shift factors resulted by the mentioned techniques, and the best fit between the measured and predicted data was found for the Numerical technique, followed by Arrhenius, Williams-Landel-Ferry (WLF), Modified Kaelble, and Log-Linear methods respectively.