Evaluation and development of a pressure aging vessel for asphalt cement
Report
Overview
Additional Document Info
View All
Overview
abstract
This study evaluates a pressure aging vessel (PAV) for asphalt cement, with the specific objectives of examining the safety of the procedure and the effects of aging temperature, film thickness on aging, vertical location within the PAV, and proximity of aging asphalt to other asphalts. Four Strategic Highway Research Program (SHRP) core asphalts (AAC-I, AAD-I, AAF-I, and AAG-I) were used in this study. An interlaboratory test program to establish the variability associated with the PAV conditioning procedure was conducted. The study indicated that the PAV operated at 71C (160F), 2.07 106 pascals (300 psi) air pressure for 144 hr, effectively simulates 2 to 10 years of pavement aging depending on the method used to measure hardening, air voids in the paving mixture, average ambient temperature, and other factors. Degree of oxidative hardening of asphalt increases with increase in temperature. For a given temperature and time of exposure, degree of hardening increases with decrease in asphalt film thickness. The vertical location of asphalt in the PAV and proximity to other asphalts had no effect on the extent of hardening. Different asphalts exhibited different rates of hardening at the same conditions of temperature and time. After this work was essentially completed, the SHRP PAV conditioning protocol was modified by increasing the temperature and decreasing the time of aging. This was done to accommodate the needs of state departments of transportation for an aging test requiring no more than 24 hr.
