Effects of water and chloride salt erosion on adhesion behavior between recycle aggregate/asphalt interface: An experimental and molecular dynamics study

Abstract

Asphalt pavements containing recycled concrete aggregates (RCA) are highly susceptible to erosion by moisture or chloride salts, leading to a significant reduction in road performance and durability. However, the erosion mechanisms of moisture and chloride salts on the RCA/asphalt interface are not fully understood. This study investigated the effects of moisture and chloride salt erosion on the bond strength of the RCA/asphalt interface using the binder bond strength (BBS) test. The underlying mechanisms were further explored through molecular dynamics (MD) simulations. The results showed that a moist environment significantly reduced the interfacial bond strength between asphalt and RCA surface mortar by 38.07 %. This is mainly due to the strong water absorption exhibited by the internal structure and surface of the mortar, and the erosion by water molecules can strip the asphalt film adhering to the RCA surface. Under NaCl solution conditions, erosive ions further significantly reduced the bond strength of the RCA/asphalt interface. This is mainly because Na⁺ ions can occupy the adsorption sites of asphalt on the RCA surface. Meanwhile, Na⁺ ions adsorbed on the RCA surface can form water clusters with water molecules, further stripping the asphalt film adhering to the RCA surface. The findings of this study will contribute to a deeper understanding of the mechanisms by which moisture and ion erosion affect the interfacial performance of RCA asphalt mixtures, providing a basis for the design and application of RCA asphalt mixtures.