Effect of increasing preheating temperature on the activation and aging of asphalt binder in reclaimed asphalt pavement (RAP)

During preheating, the activation and aging of RAP binders occur simultaneously, and both of them are closely related to the preheating temperature. The objective of this study was to investigate the effect of increasing preheating temperature on the activation and aging of RAP binder, and to find out the appropriate preheating temperature. Three sources of RAP and nine preheating temperatures (110 °C–190 °C) were included in this study. An activation test, producing 100% RAP specimens, was conducted to evaluate the binder activation. The gel permeation chromatography (GPC) test was carried out to estimate the aging level of RAP binder. In addition, the performance of hot-recycled asphalt mixture containing 30% RAP was analyzed by low-temperature splitting test, freeze-thaw splitting test, and rutting test. Ultimately, a parameter called activation-aging index (IAA) was proposed to reflect the coupling effect of activation and aging. The results indicated that increasing preheating temperature had a significant effect on the improvement of binder activation regardless of the RAP source. In addition, there was a critical temperature, beyond which the activation was difficult to be further improved. However, the increase rate of binder aging became more significant with increasing temperature, contrary to the change law of activation. As for the coupling effect, the results of recycled asphalt mixtures showed that increasing preheating temperature improved the rutting resistance, but may damage the moisture susceptibility. The low-temperature performance, however, exhibited a non-monotonic trend and had a good correlation with IAA. It is recommended to take IAA as a reference for finding the optimal preheating temperature.