An Investigation into the Continuous High-Temperature Grade and Elastic Recovery of Asphalt Binders Measured Using the Creep-Recovery Test

The multiple stress creep recovery (MSCR) test has been developed and is gradually being adopted as a more accurate indicator of the ability of an asphalt binder to resist permanent deformation compared to the G*/sin δ parameter from the Superpave binder specifications. This paper presents the findings from a study conducted using over 100 different asphalt binders from producers in and around the state of Texas. The study determined the continuous high temperature grade of asphalt binders based on the non-recoverable compliance (Jnr) measured using the MSCR test analogous to the continuous high temperature grade measured using the Superpave performance grade (PG) system. Also, the elastic recovery determined from the MSCR test was compared to the elastic recovery measured using the conventional elastic recovery test using a ductilometer. The results from this study show that: (i) some binders have an anomalous continuous high temperature grade based on the (Jnr) values, (ii) the elastic recovery measured using the MSCR method had a much higher sensitivity compared to the elastic recovery measured using a ductilometer, although the results from both methods showed similar trends, and (iii) a direct comparison of binder grades based on AASHTO M320 to the grades based on AASHTO MP19 indicated that, in some cases, the latter method and recommended specification limits result in the use of a binder that is stiffer compared to the conventional Superpave PG specification.