Characterizing the effects of aging and modification on asphalt binder bonding properties and moisture sensitivity

This study investigates the bonding performance and moisture susceptibility of asphalt binder–aggregate systems, with a focus on binder modification and aging effects. Neat asphalt binder was modified with 2 % and 4 % high-modulus polyethylene (HMPE) and styrene–butadiene–styrene (SBS). To simulate aging, the modified binders were subjected to aging processes using the rolling thin film oven (RTFO) and pressure aging vessel (PAV). Limestone and granite aggregates, selected for their contrasting mineralogical and surface energy characteristics, were used in the study. Bond strength and adhesive failure were quantified through the asphalt bond strength (ABS) test, with image analysis of the failure surfaces. Contact angle measurements were conducted to assess interfacial wettability and spreading behavior, while cohesion, adhesion, and de-bonding energies were derived using the surface free energy (SFE) approach. The results indicate that HMPE-modified binders enhance cohesive strength, interfacial wettability, and moisture resistance, with the 4 % HMPE modification yielding the most pronounced improvement. For unaged limestone systems, the 4 % HMPE modification enhanced dry and wet bond strengths by 22 % and 28 %, respectively, while the 2 % HMPE modification resulted in increases of 15 % and 6 %. HMPE modification also reduces aging-induced stiffening. After RTFO and PAV aging, the softening point of the neat binder increased by 21 % and 33 %, while the 4 % HMPE-modified binder saw increases of only 9 % and 20 %, limiting changes in cohesion energy. Image-based failure analysis further reveals a reduction in adhesive failure under both aging and moisture exposure due to HMPE modification. Additionally, HMPE-modified binders outperform SBS in terms of bonding potential, wettability, and moisture resistance. Contact angle values correlate strongly with SFE-derived spreading coefficients, bond strength ratios, and adhesive failure percentages, underscoring their reliability in predicting interfacial behavior and moisture susceptibility. The energy-based parameter also shows strong correlations with bond strength ratios and adhesive failure. These findings demonstrate that integrating thermodynamic, mechanical, and wettability analyses provides a comprehensive framework for selecting binder–aggregate systems with optimized adhesion and moisture resistance.