Chemical and Rheological Characterization of Asphalt Binders: A Comparison of Asphalt Binder Aging and Asphalt Mixture Aging

Abstract

The objective of this study was to compare the chemical and rheological properties of asphalt binders recovered from aged asphalt mixtures with the corresponding aged asphalt binders used in those mixtures. Seven plant-produced asphalt mixtures, with unmodified and polymer modified asphalt binders and varying reclaimed asphalt pavement (RAP) content, were compacted and aged in a conventional oven at 85°C for zero (unaged), five, or 10 days. Asphalt binders were extracted and recovered from each aging level for chemical and rheological characterization. Seven blends of virgin asphalt binder and RAP binder were constituted to be similar to those used in the seven plant-produced asphalt mixtures. Subsequently, each asphalt binder blend was aged by rolling thin film oven (RTFO) and pressure aging vessel (PAV) for chemical and rheological characterization. Chemical and rheological characterization included Fourier transform infrared spectroscopy, high and intermediate temperature performance grade (PG), frequency sweep, and linear amplitude sweep (LAS) tests. Asphalt mixtures aged for five and 10 days resulted in asphalt binders that were less aged than similar ones aged by PAV when measured by LAS fatigue parameter ALAS, frequency sweep Glover Rowe (G-R) parameter, and intermediate temperature PG. However, unaged asphalt mixtures yielded asphalt binders with similar properties to those aged in RTFO as measured by high temperature PG. Correlation analysis between asphalt binder and asphalt mixture aging revealed that the G-R parameter has the highest coefficient of correlation among parameters. Further, new aging indices were introduced to capture the effect of polymer modification on aging susceptibility.