Asphalt binder experiences aging during mixture production and the service life of the pavement. Aging of asphalt binder directly influences the stiffness and damage resistance of asphalt mixtures. The current industry practice is to simulate short-term and long-term aging in asphalt binders using the rolling thin-film oven (AASHTO T 240) and pressure aging vessel (AASHTO R 28), respectively. These methods and the parameters (e.g., aging temperature, pressure, and duration) involved in their use were developed a few decades ago for neat binders produced from conventional crude oil sources; they were adopted as standards primarily to aid performance grading of asphalt binders. Over the last few years, there have been several significant changes in asphalt technology. The use of warm mix asphalt and reclaimed asphalt pavements has significantly increased. The use of additives and chemical and polymer modifiers to enhance binder properties has also greatly increased; in some cases, the oxidation kinetics of such modified binders are significantly different from that of conventional binders. Stiffer binder grades may experience insufficient oxidation in the laboratory aging process. Finally, studies have confirmed that a better understanding of binder aging and oxidation can improve our ability to predict damage in asphalt pavements. In light of the above changes in asphalt technology, research is needed to develop new or improved short- and long-term binder aging methods to accurately reflect the aging in asphalt mixtures not currently captured by AASHTO T 240 and R 28.
The objective of this research was to develop practical laboratory aging methods to accurately simulate the short-term (from production to placement) and long-term (in-service) aging of asphalt binders. The research shall determine the relationship between different methods of laboratory aging of asphalt binders and the actual aging that occurs during mixture production, transport, and placement as well as during the service life of the pavement structure.
STATUS: The project final report is available as NCHRP Research Report 967: Asphalt Binder Aging Methods to Accurately Reflect Mixture Aging.