INFRARED STUDY OF THE AGING OF ASPHALTS IN CONTACT WITH AGGREGATES. IN: AMERICAN CHEMICAL SOCIETY SYMPOSIUM ON CHEMISTRY AND CHARACTERIZATION OF ASPHALTS, AUGUST 1990, WASHINGTON, D.C.

The purpose of this work was to identify chemical compound types produced at or near the asphalt/aggregate interface during oxidative aging. Diffuse reflectance infrared Fourier transform (DRIFT) spectrometry was used to analyze samples of asphalt that had oxidatively aged in contact with aggregate for various periods of time. Aging products were studied as a function of time, distance from the aggregate surface, asphalt composition, and aggregate composition. Three compound types were observed to form upon aging -- sulfoxides, ketones, and carboxylic acids. All three compound types are thought to cause hardening and cracking of asphalts. The composition of the virgin asphalt was a key factor in determining the kind and amounts of aging products formed. The amount of products formed was also related to aging time. Evidence for the concentration of any one aging product on or near the asphalt/aggregate interface was not found.