CHEMICAL CHARACTERIZATION OF ASPHALT CEMENT AND PERFORMANCE-RELATED PROPERTIES

Gel permeation chromatography (GPC), the Corbett analysis procedure (ASTM D 4124-82), and the Heithaus test for component compatibility have been used to characterize asphalts and to investigate relationships among these chemical properties and physical properties and performance. The asphalts used in the present study were periodic samples of virgin asphalt from various suppliers in Texas, test pavement asphalts from three locations in Texas, and a group of 12 asphalts that had been rated according to pavement tenderness. GPC chromatograms, using toluene or tetrahydrofuran (THF) as the carrier solvent, show significant differences from one supplier to the next. Differences in chromatograms for a single supplier over a period of time may be quite significant. Furthermore, the differences between toluene and THF chromatograms are considerable and can likely be used as supplementary analyses. Finally, differences in viscosity grades (for a given refiner at a given time) frequently may be detected as differences in the shapes of the GPC chromatograms. For virgin asphalts from the Texas test sections, viscosity temperature susceptibility was found to correlate quite well with the molecular size fractions of the GPC chromatograms using either toluene or THF as a carrier solvent. Studies of pavement tenderness showed a relationship between component compatibility and tenderness and between the GPC large molecular size fractions and tenderness. In addition, asphaltene content was found to relate to component compatibility and to tenderness. Finally, as a cross correlation, the large molecular size region of the GPC chromatograms is directly related to the asphaltene content of asphalts with the exception of the Texas Diamond Shamrock asphalt.