Investigation on the low temperature properties of asphalt binder: Glass transition temperature and modulus shift factor

Abstract

This paper investigates the effect of the glass transition temperature, Tg, and the use of modulus shift factors bT on the measured rheological properties of asphalt binders at low temperatures. First, temperature-frequency (T-f) sweep tests are performed with the Dynamic Shear Rheometer (DSR) on asphalt binder, and, the corresponding Tg is calculated. Next, modulus shift factors bT is applied to the modulus data measured at temperatures below Tg in the Cole-Cole plot. Finally, a visual comparison of master curves and the parameter assessment of 2 Spring 2 Parabolic 1 Dashpot (2S2P1D) model are used to evaluate the effect of bT. A significant increase in dynamic shear modulus is observed when the DSR test is performed below Tg, while bT can take into account this phenomenon on the shape of the curves in the Cole-Cole plot. Hence, the combined use of the horizontal shift factor, aT, and modulus shift factor, bT, is recommended when the DSR tests are performed at temperatures lower than the corresponding asphalt binders Tg.