Developing an aging model to evaluate engineering properties of asphalt paving binders

Oxidative aging of asphalt is a primary cause of binder hardening in pavements, thus contributing to various forms of pavement failures. An essential element of predicting long-term pavement performance is to understand binder oxidative aging and its effect on engineering properties. Five asphalt binders were evaluated relative to their changes in engineering and chemical properties in pavement service. Laboratory rolling thin-film oven test (RTFOT) and pressure aging vessel (PAV) test were conducted to simulate the in-situ pavement aging. In addition, a test road was constructed for this study to investigate the real aging process in the field. Comparable data were shown between field binders and laboratory binders aged at temperature 60°C under pressure 20 kg/cm². The aging time of asphalts in PAV depended on how long pavements were used in the field. This paper was to determine the temperature and pressure used for PAV to simulate aging condition in the field. A good correlation between field-service and laboratory aging during test road project was found. An aging model was proposed to predict the changes in paving binder's properties during field age hardening. Results were shown to give a close fit with experimental data from both laboratory and field aging tests. This model allowed highway engineers to quantify two essential characteristics of binder aging: the aging rate and the ultimate degree of changes in binder properties due to aging.