Evaluation of hydrothermal sensitivity of different asphalts in static and dynamic water environments based on DSR and FTIR

Asphalt pavements in humid and rainy regions are highly susceptible to water-induced damage. Unlike traditional studies that primarily focus on static water conditions, asphalt pavements in service are more realistically exposed to dynamic pore water induced by repeated vehicle loading, which can be simulated using the Moisture Induced Stress Tester (MIST). Existing studies on moisture effects in asphalt binders mainly concentrate on asphalt–aggregate adhesion or binder properties under static water exposure, whereas systematic evaluations of hydrothermal sensitivity under dynamic water conditions and the associated mechanisms remain limited. To address this gap, this study employed Dynamic Shear Rheometer (DSR) tests—including temperature sweep, multiple stress creep recovery (MSCR), linear amplitude sweep (LAS), and tack tests—together with Fourier transform infrared spectroscopy (FTIR). The ratios of key rheological parameters and functional group indices before and after water conditioning were defined as hydrothermal sensitivity indices. These indices were used to evaluate and compare the hydrothermal sensitivity of a base asphalt (70#), an SBS-modified asphalt (I-D), and a high-viscosity modified asphalt (HVMA), as well as to analyze the correlations among different performance-related sensitivity indicators. The results show that short-term water conditioning enhances the rutting factor, reduces the irrecoverable creep compliance, and increases the cohesive work of asphalt binders, while deteriorating their fatigue resistance. Dynamic water exposure exerts a more pronounced influence on binder properties than static water conditions. Compared with the base asphalt, the SBS-modified asphalt (I-D) and HVMA exhibit higher hydrothermal sensitivity. FTIR analysis reveals that the polar components introduced by SBS modification are more prone to interact with water molecules under hot and humid conditions, providing a mechanistic explanation for the higher hydrothermal sensitivity of I-D and HVMA. Correlation analysis further demonstrates the feasibility and effectiveness of the proposed dynamic hydrothermal sensitivity evaluation approach.