<p>Asphalt concrete is widely used as the impervious facing of hydraulic dams under long-term water storage, and its resistance to moisture damage is closely associated with structural safety. This study focuses on two typical hydraulic environments—long-term immersion and immersion followed by drying—and systematically evaluates the moisture damage resistance of asphalt binders and mixtures. FTIR, DSR, and uniaxial compression tests were employed to characterize, respectively, the chemical composition of the binders, their cohesive performance, and the water stability of asphalt mixtures. In addition, the initial adhesion index, originally developed in the pressure-sensitive adhesive field, and 3D laser scanning for quantitative characterization of surface morphology evolution were introduced to evaluate asphalt–aggregate interfacial adhesion and the water sensitivity of asphalt mixtures, respectively. The results showed that water ingress into the asphalt film interacted with oxygen-containing functional groups and accelerated oxidation, thereby promoting progressive aging. Although the cohesive performance increased, the interfacial adhesion continuously deteriorated; during post-immersion drying, residual water within the film and atmospheric oxygen further promoted this process. After drying, the compressive strength of the asphalt mixtures partially recovered; however, the water stability coefficient remained below 1, indicating that the moisture-induced damage could not be fully reversed. Water sensitivity coefficients derived from 3D scanning—including volumetric change and surface deformation—captured the cumulative deformation of specimens during immersion and post-immersion drying. Notably, <i>M</i>_<i>n</i>, which characterizes the evolution of surface relief, provided strong discriminatory power, suggesting that it is a preferred indicator of moisture damage resistance.</p>