Improved test method for determination of the equiviscous temperature of asphalt binders

In CEN/TS 15324 (2008), the equiviscous temperature (EVT) of an asphalt binder was recognized as a potential rutting indicator. A test method, which consisted of temperature sweep and frequency sweep, was developed to determine the EVT based on the concept of low shear viscosity (LSV). In this study, this test method was firstly evaluated in terms of its applicability. Several deficiencies were identified, which suggested the importance of determining the EVT of asphalt binders based on the actual zero shear viscosity (ZSV). Given the shortcoming of the test method in CEN/TS 15324 (2008), the objective of this study was to develop an improved test method for the determination of EVT of asphalt binders. A new test method, named as ZSV-based test method, was then proposed based on the shear rate sweep test and the Arrhenius equation. The ZSV-based test method consisted of three steps: temperature sweep, shear rate sweep and temperature sweep. Two neat asphalt binders and two SBS-modified asphalt binders were tested using the proposed test method, and the EVT of each asphalt binder was estimated using the Arrhenius equation. The EVT values determined using the proposed test method were demonstrated to be reliable and repeatable.