Effect of Asphalt Binder Modification Type on Low Temperature Performance Determined Using Asphalt Concrete Cracking Device (ACCD)

Abstract

For current asphalt paving practice, many unconventional asphalt binders and additives have been introduced. Through physical and chemical interactions with base binders, these modifications usually affect the binder and mix strength and fracture properties as well as stiffness. However, the currently used binder grading system is based on the low temperature stiffness and relaxation behavior as measured using the Bending Beam Rheometer (BBR). The absence of strength and fracture properties in the asphalt binder grading process may result in inaccurate prediction of field performance. Five PG grade asphalt binders including unmodified, polyphosphoric acid (PPA) modified and styrene-butadiene-styrene (SBS) modified binders were tested using the BBR and the Asphalt Binder Cracking Device (ABCD). Asphalt mixes prepared with these five binders were also tested with a revised Asphalt Concrete Cracking Device (ACCD) test procedure. The test results showed improved strength and fracture resistance characteristics for SBS modified asphalt binders in the ABCD test and mixtures in the ACCD test, resulting in better performance than that predicted by the BBR low temperature PG grade. However, the PPA modified asphalt binder and the corresponding mixture exhibited worse performance in the ABCD and ACCD tests, respectively, than that predicted by the BBR low temperature PG grade, which may be attributed to the poor fracture resistance.