Evaluation of rutting resistance and moisture susceptibility of high RAP content asphalt mixtures containing bio-based rejuvenators

Abstract

Hot Mix Asphalt (HMA) incorporating high Reclaimed Asphalt Pavement (RAP) contents can potentially have good rutting resistance due to the higher stiffness of the aged RAP-binder. The use of rejuvenators to enhance the workability and performance of high RAP mixes is becoming a common practice. However, the impact of rejuvenators on the rutting resistance and moisture susceptibility of high RAP mixes has not been studied exhaustively. The Hamburg Wheel-Tracking (HWT) test was used in this study to evaluate the asphalt mixture performance in terms of their resistance to permanent deformation and moisture damage at two conditioning temperatures of 44℃ and 50℃. Highly recycled asphalt mixes containing 50% RAP were prepared with various bio-based rejuvenators and a soft binder to compare with a control mix with 20% RAP content. Different HWT data analysis methods were used to quantify the mix performance. The results indicated that the rejuvenated high RAP mixes showed increased rut depth and higher possibilities of stripping compared to the control mix and the 50% RAP mix without rejuvenators. Regardless of the rejuvenator type and dosage, both the control and the rejuvenated high RAP mixes experienced severe stripping due to the increase in testing temperature. The 50% RAP mix performed best at both test temperatures. Therefore, caution is warranted concerning the adverse effects of rejuvenators or soft binders on the rutting performance and moisture susceptibility of high RAP mixes. Furthermore, traditional HWT parameters could be misleading due to the confounding effects of post-compaction and moisture-induced deformation. Parameters developed by the novel HWT data analysis methods could separately evaluate the rutting resistance and moisture susceptibility.