Use of Accelerated Natural Aging to Simulate Long-Term Asphalt Binder Aging in Pavements

Asphalt binder is prone to aging in usage conditions. Although aging an asphalt binder using a pressure aging vessel (PAV) is a popular method to simulate the long-term aging of the binder, questions have been raised about the accuracy of this method. This research is focused on (i) examining the detailed physicochemical aging processes of asphalt binders aged in a relatively natural condition, (ii) evaluating the effects of supporting medium on asphalt binder aging, (iii) comparing aging trends of binders from different crude sources, (iv) modeling and forecasting the long-term aging behaviors of asphalt binders. Seven types of neat asphalt binders were studied, and two types of supporting media were used. The natural aging condition was set to be 60 degrees C in a dark environment, and the thickness of the asphalt film was reduced to about 0.8 mm. The longest natural aging treatment duration was 75 days. Samples were periodically taken to test their physicochemical properties. The binders were also subjected to PAV treatments for comparison purposes. It is found that most physicochemical properties of the naturally aged binders exhibit a fast change stage followed by a relatively slow change stage. At the slow change stage, commonly used properties can be predicted well through linear models. In general, PAV aging does not reflect well the aging trends and characteristics of binders treated in the more natural conditions. Therefore, it is proposed to consider using natural aging to simulate asphalt binder aging for road pavements with high expectations on durability.