Experimental Study on RAP with High Recycling Content Based on High-Modulus Asphalt Mixture

To improve the recycling content of Reclaimed Asphalt Pavement (RAP), this paper utilizes the characteristic of aged and hardened asphalt in RAP materials by adopting the High-modulus Asphalt Mixture design method for high-RAP-content recycling. First, the basic technical performance, fatigue properties, rheological characteristics, and chemical functional groups of reclaimed asphalt, 30# hard asphalt, and Styrene-Butadiene-Styrene (SBS)-modified asphalt were analyzed. The results revealed significant similarities in various metrics between reclaimed and hard asphalt, demonstrating the feasibility of replacing hard asphalt with reclaimed asphalt in a High-modulus Asphalt Mixture design. Next, High-modulus Asphalt Mixtures, EME13, with different RAP contents (0%, 20%, 40%, 60%) were designed and compared with SBS-modified Sup13 mixtures. The results indicated that (1) as the RAP content increased, the high-temperature performance of EME13 improved by 20~60%, while its low-temperature and intermediate-temperature crack resistance slightly declined by 10~20%. The dynamic modulus in the low-frequency region increased by 3~6 times, whereas the high-frequency dynamic modulus decreased by 20~30%. RAP enabled EME13 to meet the modulus design requirements more readily for High-modulus Asphalt Mixtures. (2) Although the SBS-modified Sup13 exhibited superior pavement performance compared to EME13, its cost was significantly higher. EME13 with high RAP content demonstrated notable economic advantages despite slightly lower pavement performance than Sup13. This research provides a new technical approach for the high-content recycling of RAP materials.