Moisture Damage Mechanism and Material Selection of Hma with Amine Antistripping Agent

This study investigates the moisture damage mechanism and material selection of hot-mix asphalt (HMA) with amine-based liquid antistripping agent (ASA). The surface free energy (SFE) of virgin and ASA modified asphalts and five aggregates with different acidities were measured, yielding the compatibilities of different asphalt-aggregate combinations and the working mechanism of amine ASA. The use of amine ASA changed the thermodynamic properties of asphalt by decreasing the nonpolar components and increasing the polar components, which enhanced the work of adhesion between asphalt and aggregate and reduced the free energy released at the presence of water. The wettability of asphalt over aggregate was also increased due to the ASA, suggesting a better coating quality of asphalt mixtures was achieved. All those changes led to the increased energy ratio (ER), indicating the improved moisture resistance and compatibility of materials. At the molecular level, it might be because the amino groups from ASA adsorbed the silanol groups at the aggregate surface, leading to a stronger bond between asphalt and aggregate.