Research on Salt Freeze Thaw of Concrete Based on Multi Field Coupling Model

This paper presents a trans-scale finite element model based on hydraulic-thermal-mechanical coupling equations of porous medium to simulate the behavior of concrete during salt freezing and thawing. The Mori-Tanaka method was employed to homogenize the mechanical and thermodynamic parameters of the mortar and interfacial transition zone (ITZ), simplifying model development and subsequent calculations. The homogenized parameters were then incorporated into a three-phase concrete model to simulate both concrete freeze-thaw cycles and salt freeze- thaw cycles. The model was used to analyze changes in pore pressure, temperature field, displacement deformation, and stress distribution in concrete under freeze-thaw cycles. The results revealed that freeze-thaw damage initially occurs in the ITZ, which exhibited increased susceptibility to cracking due to its overlap with Darcy flow lines and higher pore pressure and von Mises stress compared to the concrete mortar matrix. Under salt freezing conditions, the pore pressure, maximum vertical displacement, and von Mises stress in concrete were significantly higher than under water freezing conditions, leading to more severe freeze-thaw damage and earlier failure of the concrete.