New Low-Temperature Performance-Grading Method

Abstract

Mechanical measurements on asphalt binders to determine the performance grade of the low-temperature specification are typically carried out with a bending beam rheometer (BBR). The BBR test requires considerable material to fabricate a specimen (approximately 15 g per beam). The relatively large amount of asphalt binder required for the BBR limits its applications. The BBR is difficult to apply to extracted asphalt binder or to other situations in which there is a limited amount of binder, for example, residue from emulsions. This paper proposes an alternate mechanical test to the BBR to determine low-temperature PG. Only approximately 25 mg of asphalt binder are required to perform a test. The test employs 4-mm-diameter parallel plates on a dynamic shear rheometer (DSR) and includes a correction for machine compliance. This correction allows testing to −40°C. A low-temperature specification from the 4-mm rheometry is suggested by the establishment of a correlation between BBR creep stiffness data and DSR stress relaxation data. The shear stress relaxation data used in this work were interconverted from dynamic frequency sweep data. A strong linear correlation was observed between BBR and DSR data from 11 asphalt binders.