Effects of Refined Disposal on High RAP-Recycled Asphalt Mixtures: Virtual Analysis and Experimental Investigation into Shear Strength and Road Performance

ABSTRACT The aged asphalt mortar the reclaimed asphalt pavement (RAP) attaches to the aggregate surface and results in serious particle agglomeration. The agglomerated particles make it difficult to blend the new and aged binders, thus seriously limiting the use of RAP. To address the problem of particle agglomeration, the RAP-refined disposal equipment was used to separate the aged asphalt film from the aggregate surface and achieve fully disposed RAP. However, the evolution of RAP properties during the refined disposal process, especially the morphological features of recycled aggregates in RAP, cannot be ignored. Additionally, the shear strength and road performance of the recycled asphalt mixture following RAP-refined treatment are still unknown. In this research, the three-dimensional (3-D) reconstruction model of refined recycled aggregates was constructed by 3-D scanning and the Overlapping Discrete-Element Cluster (ODEC) algorithm. Additionally, a virtual uniaxial penetration digital model was established based on a real asphalt mixture. The shear strength of recycled asphalt mixtures with various RAP contents was thoroughly investigated at macro and meso scales using the virtual uniaxial penetration test. In addition, the properties of strength development of high RAP-recycled asphalt mixture were comprehensively evaluated through wheel tracking test, three-point bending test, and immersed Marshall test. The results showed that after refined disposal, the aggregate surface texture index was significantly increased, with a notable increase in the new and aged binders’ miscibility and an improvement in the recycled asphalt mixture’s road performance. However, when refined RAP content exceeds 75 %, the rising percentage of aggregates with poor angularity and needle-like particles increases, which hinders the interlocking of aggregates within the recycled asphalt mixture, leading to a significant deterioration in its road performance.