Verification of an Asphalt Aging Test and Development of Superior Recycling Agents and Asphalts (1314-1F)

This study included an in-depth investigation of asphalt oxidation hardening and accelerated aging tests to simulate asphalt hardening on the road. A very significant finding is that the effect of both temperature and pressure on hardening rates is very asphalt dependent, so that any test run at a single elevated temperature or pressure can be very misleading. Equations are given which express asphalt oxidation as a function of both temperature and pressure which, with sufficient data, permit calculations at ambient conditions. Test section studies indicate that actual road aging is considerably slowed by diffusion resistance. Extensive studies were conducted on compositional effects in recycling. Hardening in asphalt is almost totally due to asphaltene formation. Recycling agents should be asphaltene free and low in saturates. Good mixing rules were developed for asphaltene free agents. In general, asphaltene-free agents lowered the blend viscosity more than would normally be predicted from the agent viscosity. Aging studies on recycled material produced good results with some commercial agents as well as with fractions obtained by supercritical fractionation of asphalts.