Adhesive properties between recycled concrete aggregate and asphalt

The unique surface microscopic morphology (SMM) and chemical composition of recycled concrete aggregate (RCA) would affect its adhesion to asphalt. This research utilized a laser microscope system (LMS) and atomic force microscopy (AFM) to examine the SMM parameters and surface energies of RCA and asphalt, respectively. Pull-off tests were conducted to assess the macroscopic adhesive strength between RCA and asphalt. Additionally, the impact of SMM and surface energies on the materials concerning this macroscopic adhesive strength was investigated. In the final phase, this study explored the multi-scale adhesion mechanisms between RCA and asphalt. Research indicates that an increase in grade correspondingly elevates the surface roughness and surface energy of the asphalt. For asphalt containing bee-like structures, the surface energy in other regions surpassed that of the convex part and concave part. With the increase of water-cement ratio of RCA, the SMM roughness increases, and the surface energy decreases. The adhesion of RCA to asphalt is the result of both physical and chemical adhesion, 60% from chemical effect and the remaining about 40% from physical effect. • SMM roughness and surface energy of asphalt are influenced by oil source and grade. • SMM roughness and surface energy of RCA are related to water-cement ratio. • Approximately 60% and 40% of the adhesion between RCA and asphalt are attributed to the physical and chemical interactions.