Rheological properties of asphalt binders modified with styrene-butadiene-styrene (SBS), ground tire rubber (GTR), or polyphosphoric acid (PPA)

In this study, the rheological properties of modified binders have been investigated. For this purpose, varying amounts of styrene-butadiene-styrene (SBS), ground tire rubber (GTR) or polyphosphoric acid (PPA) modifiers were added to a neat binder. The dynamic shear rheometer (DSR) was used to grade the original, RTFO-aged and PAV-aged binders based on the conventional performance grading (PG) and the multiple stress creep recovery (MSCR) systems. The bending beam rheometer (BBR) was used to study the low-temperature properties of the asphalt binders. All of the modifiers were found to improve the high temperature properties of the neat asphalt. With regard to the intermediate temperatures, SBS and PPA did not significantly affect the performance of the binder. However, GTR significantly decreased the stiffness of the binder. In addition, these modifiers were not found to have significant effects on the low temperature continuous grade of the binders. The MSCR protocol was successfully used to grade all the binders; however, the “percent difference” criterion of the MSCR protocol seems to be not applicable with regard to some binders and conditions.