SUPERCRITICAL FRACTIONS AS ASPHALT RECYCLING AGENTS AND PRELIMINARY AGING STUDIES ON RECYCLED ASPHALTS

Several asphalts were fractionated using supercritical pentane. These fractions were analyzed by gel permeation chromatography and high-perf ormance liquid chromatography, and their viscosities were measured. Th e properties of these fractions vary not only among the fractions of a given asphalt but also for the same fraction produced from different asphalts. These widely varied fractions previously have been shown to have potential for reblending to produce superior asphalts. This study investigates the potential for using some of the fractions as asphalt recycling agents. A modified strategic highway research program (SHRP ) pressure aging vessel (PAV) test and kinetics studies were conducted on nine recycled asphalts and the original asphalt. The aging indexes of eight of the recycled asphalts are superior to the aging index of the original asphalt. Two of the blends using industrial supercritical fractions and the three blends using laboratory supercritical fractio ns have lower aging indexes than blends using commercial recycling age nts. The kinetics investigation also indicates that at road conditions the recycled asphalts will harden more slowly than the original aspha lt. The degree of hardening for a given amount of oxidation in the rec ycled binders was found to be a strong function of the total saturate content in the recycled binder.