Assessment of moisture diffusion in hydraulic asphalt under coupled hydrothermal conditions

Abstract

To analyze the moisture penetration behavior in asphalt and investigate the variation trend of moisture infiltration under the coupled effects of different temperatures and exposure durations, this study employed electrochemical impedance spectroscopy (EIS) and Fourier transform infrared spectroscopy (FTIR) to examine moisture penetration in base asphalt and SBS-modified asphalt, two typical types of asphalt, under a hygrothermal environment and its impact on material properties. The results indicate that with increasing immersion time, the capacitance of asphalt continuously rises, while electrochemical impedance significantly decreases. This effect is particularly pronounced at high temperatures, where the reduction in impedance radius and the decline in low-frequency slope suggest an accelerated moisture diffusion rate. Additionally, SBS-modified asphalt initially exhibits higher impedance values and a slower capacitance growth rate. However, the degradation of the SBS network structure at elevated temperatures leads to a deterioration in its moisture resistance, making its long-term water permeability worse than that of base asphalt. In the FTIR analysis, the hydroxyl characteristic peak intensifies significantly with moisture infiltration, exhibiting an initial slow increase followed by a rapid rise. This suggests that the strong interaction between moisture and polar groups in asphalt accelerates microstructural changes. This study demonstrates that EIS effectively reveals the moisture diffusion kinetics and its influence on electrochemical properties, while FTIR provides direct insights into the interaction mechanism between moisture and asphalt molecules. The combined use of these two methods facilitates a precise assessment of moisture penetration behavior in asphalt.