Rheological properties degradation of asphalt mastic under NaCl erosion-freeze-thaw cycles: Damage contribution calculation via freezing pressure theory

In coastal and seasonally frozen regions, asphalt pavements deteriorate rapidly due to the combined effects of moisture infiltration, freeze-thaw (F-T) cycles, and salt erosion, yet the underlying mechanisms remain unclear. This study examines the migration of the complex modulus master curve, low-temperature stress relaxation, asphalt-filler interaction, and morphological evolution of three asphalt mastics (70#, 90#, and SBS modified) under NaCl erosion-freeze-thaw (S-F-T) cycles, using dynamic shear rheometer (DSR) and atomic force microscopy (AFM) tests. The most adverse S-F-T conditions were identified by the Analytic Hierarchy Process-Entropy Weight Method (AHP-EWM), and a freezing pressure theory-based calculation quantitatively evaluated the damage contributions of salt erosion and F-T cycles. Results show that the S-F-T cycles diminished the viscous dissipation capacity while enhancing the elastic properties, while deteriorating low-temperature stress relaxation. AFM revealed the fading of bee-like structures and surface deterioration. The most severe S-F-T damage for 70#, 90#, and SBS asphalt mastics occurred at salt concentrations of 5 %, 10 %, and 10 %, respectively. Higher salt concentrations reduce freezing pressure and F-T damage, while salt erosion becomes dominant. The proposed F-T damage reduction factor quantified salt erosion and F-T damage contributions under various S-F-T cycle conditions. Combined with logistic and energy dissipation models, the viscoelastic degradation of three asphalt mastics was efficiently predicted under 70 S-F-T cycles. The significance lies in its quantitative evaluation of the damage contributions of salt erosion and freeze-thaw cycles based on the typical damage characteristics of asphalt mastics under S-F-T conditions. The findings provide a theoretical basis and technical support for enhancing the salt-freeze resistance of asphalt pavements in coastal and seasonally frozen regions, such as optimizing materials selection and developing novel materials with improved S-F-T resistance. Therefore, this research provides valuable engineering guidance for prolonging the service life of asphalt pavements in challenging environments.