ROLE OF ASPHALT AND AGGREGATE IN THE AGING OF BITUMINOUS MIXTURES

The development of short- and long-term aging procedures has been ongoing at Oregon State University under Strategic Highway Research Program (SHRP) Project A-003A. In the first phase of this project several alternative methods for short- and long-term aging of asphalt-aggregate mixtures were examined. From these, one short-term method and two long-term procedures were chosen to be examined further in the second phase of the project. For short-term aging a procedure of curing the loose mix in a forced-draft oven at 135 deg C for 4 hr was chosen. Two procedures were used to evaluate the effects of long-term aging: low-pressure oxidation at 60 deg and 85 deg C for 5 days and long-term oven aging at 85 deg C for 5 days and 100 deg C for 2 days. The evaluation was done in an extensive testing program using eight asphalts and four aggregates. The results of the asphalt-aggregate mixture testing presented in this paper show that the aging of the mixture is dependent on both the asphalt and the aggregate. Also, it appears from the evaluation of data from other SHRP contractors that the aging and subsequent testing of asphalt alone are not good predictors of the effects of the asphalt-aggregate interaction on mixture behavior.