Aging of Bitumen and Asphalt Concrete : Comparing State of the Practice and Ongoing Developments in the United States and Europe

Aging is a crucial factor in pavement performance and being able to determine its effect on a mixture is necessary to link its initial properties to the properties over time in order to ensure the intended service life. This is becoming more important now that climate change leads to increased variation in weather conditions, while environmental considerations cause changes in the constituent materials that are used. As a result, past experience is becoming less reliable. In this paper, the USA and European approaches to aging are compared, showing that those contain the same test equipment and almost identical conditions for aging. This allows the exchange of data and experience. The current tests are suitable for binders and give an indication of the sensitivity to aging. For short term aging, Rolling Thin Film Oven Test (RTFOT) conditioning gives a reasonable indication of bitumen aging during asphalt concrete production and construction. This only holds for penetration grade binders during hot mix production and construction. For long term aging, because of the many variables involved, developing a single test method to characterize aging sensitivity seems impossible. However, using more elaborate protocols in existing, practical tests can provide more information and the necessary input for kinetic aging expressions. A pressure aging vessel (PAV) protocol for testing at two temperatures and time intervals, specifically at 90 and 100 degrees Celsius and for 20 and 40 hours, respectively, is suggested. Using the same conditioning in characterizing materials for pavement construction and research will facilitate the exchange of data and enable faster developments.