Changes in Chemical Fingerprints of Asphalt Binders Due to Aging

Abstract

Asphalt binders remain exposed to aging from mixing and placement operations throughout their service life. The aging process is a chemical event, often known as oxidization, which hardens asphalt binders by causing changes to their chemical compositions. Stiffening also occurs when they are modified chemically to make them fit in certain environmental and loading conditions. Aging can accelerate stiffening of the modified binders because of the simultaneous presence of the modifier and oxidizing agents. This study evaluates the changes in the chemical fingerprints of asphalt binders in terms of their Saturates, Aromatics, Resins, and Asphaltenes (SARA) fractions and Fourier Transformation Infrared Spectroscopy (FTIR)—based functional groups. Two selected performance grade (PG) binders (PG 64-22) modified with Polyphosphoric Acid (PPA) and Styrene Butadiene Styrene (SBS) have been subjected to Rotational Thin Film Oven (RTFO) and Pressure Aging Vessel (PAV) aging. Asphalt binders from two different crude sources modified with different percentages of PPA, SBS and a combination of PPA and SBS were considered in this study. Due to the aging effects, the modified asphalt binders became abundant in solid phase than the unaged binders at a lower modification level, which in turn made the binders stiff. The changes in pattern were different for binders from two different crude origins. The findings from this study can help setting guidelines for level of chemical modification to asphalt binders.