Relating Asphalt Field Aging Over a 10-Year Period to Simulated Laboratory Aging

Asphalt aging has been an important topic for decades, but in recent years many factors have further heightened emphasis on aging specifications. These factors may include but are not limited to the inertia to recycle, changing markets where more materials are placed near surfaces, mixes becoming more brittle and crack prone, and large price increases for virgin binders. The objective of this paper is to develop quantifiable relationships, for several binder properties, between hours of pressure aging vessel (PAV) conditioning and mixture field aging in a hot and non-freeze climate. Nine binders, 12 mixture variations, up to 10 years of field aging, and up to 160 PAV hours were included in the experimental matrix. Findings showed that the American Association of State Highway and Transportation Officials (AASHTO) R28 was able to simulate over 5 years of field aging with 20 PAV hours at 100°C when aging occurred at a depth of 5 to 6.3 cm from the pavement surface, but not when within 1.3 cm of the surface. The aging rate was roughly three times higher at the surface than at 5 to 6.3 cm deep. Air voids had over twice the impact on binder property changes at 5 to 6.3 cm deep than within 1.3 cm of the surface. R28 should consider modifying the significance and use portion of the standard to reflect that mixes within 1 to 2 cm of the surface are very unlikely to have 5 years of aging simulated by 20 PAV hours at 100°C.