Study on the effects of reversible aging on the low temperature performance of asphalt binders

Abstract

Reversible aging refers to a time-dependent stiffening of asphalt binder that results from the time-delayed increase in stiffness when the asphalt binder is stored at low temperatures. The increase in stiffness will distinctly affect the low temperature performance of the asphalt binder, but existing researches rarely consider this. This paper aims to investigate the effects of reversible aging on the low temperature performance of asphalt binders, and to reveal the underlying mechanism of reversible aging. To this end, four different types of asphalt binders were selected for the extended bending beam rheometer (EBBR) test at different conditioning times. The thermal stress was computed based on the rheological data obtained from the EBBR test to quantify the influence of low temperature reversible aging on the cracking resistance of the asphalt binders. The Avrami isothermal crystallization kinetics theory was used to analyse the reversible aging process of asphalt binders from the perspective of macro-crystal structure. Furthermore, the molecular dynamics was performed to simulate the reversible aging process of asphalt binders from a microscopic point of view. The results from this study show that the low temperature performance of asphalt binders continues to decline with the extension of the conditioning time, which is manifested by the increase in grade loss, thermal stress and critical cracking temperature. Reversible aging exhibits great impact on the low temperature performance of asphalt binders by lowering the low temperature grade of asphalt binders up to one grade. The Avrami isothermal crystallization kinetic theory can accurately characterize the reversible aging tendency of asphalt binders. The molecular dynamics simulation results show that the asphaltene component contributes the most to the reversible aging of asphalt binder.