Determination of Binder Glass Transition and Crossover Temperatures using 4-mm Plates on a Dynamic Shear Rheometer

Abstract

The accurate rheological characterization of asphalt binder properties, as a function of pavement service life, is crucial to improving asphalt binder specifications, modifications, and formulation methods. Bitumen streams from refineries have experienced significant changes since the development of SHRP Superpave specifications as a result of economic, technical, and environmental reasons. Binder rheological behavior is divided into three regions: near glassy region, terminal region, and an intermediate “transition” region between them. At a reference frequency, these regions are separated by two characteristic temperatures: (1) the glass transition temperature (Tg), which is the temperature between the near glassy region and the intermediate region, and (2) the crossover temperature (TG’=G”), which is the temperature between the intermediate region and the terminal region. In this study, Tg and TG’=G” of 50 binders were obtained from a dynamic shear rheometer (DSR) using 4-mm parallel plates. Glass transition temperatures from DSR were compared with those obtained from modulated differential scanning calorimetry (DSC). Tg and TG’=G” were also compared with continuous low-PG temperatures and ΔTc parameter. Results indicate that critical temperatures based on the creep stiffness and the relaxation rate can be determined from Tg and TG’=G”, respectively. Furthermore, ΔTc parameter correlates well with the intermediate region temperature range (TIR).