Aging mechanism of SBS modified asphalt based on chemical reaction kinetics

• The dynamic equation based on rheological measurements was used to analyze the aging mechanism.
• The activation energy of asphalt is not a constant and will change along with aging.
• We examine changes of molecular structure of asphalt under different aging states.

Research on aging mechanism of SBS modified asphalt can provide theoretical and technical support not only for the choice of asphalt pavement materials but also for recycling of SBS modified asphalt pavement. Dynamic equations of asphalt under different aging conditions were respectively established according to chemical reaction kinetics. And two kinds of micro analysis methods, component analysis and GPC (gel permeation chromatography), were used to analyze the change of asphalt composition and asphalt molecular structure during the aging process. In addition, the correlation between activation energy and asphalt microscopic components, asphalt molecular structure was analyzed through grey entropy theory analysis method. Different from previous research, the results demonstrate that the activation energy of asphalt is not a constant index. SBS network structure loses gradually due to the degradation of SBS modifier during the aging process. SBS modified asphalt after short-term aging degrades to more medium molecular size structure, which makes the activation energy become lower and improves asphalt temperature sensitivity. However, the SBS modifier after long-term aging has almost degraded completely, which increases the activation energy and makes asphalt temperature sensitivity approximate to base asphalt. The results of grey entropy theory analysis show that the activation energy will be reduced with the decrease of saturate content, the increase of medium molecular size structure content and resins content.