Numerical Analysis and Poromechanics Calculation for Saturated Mortar Involved with Sub-Freezing Temperature

The individual coupling processes of two-phase materials are controlled to some extent by damage theory. However, the existing theory is not sufficient to explain the effect of pore pressure on mortar materials under freeze-thaw action. In order to predict the resistance of saturated mortars during rapid cooling and to describe the physical behavior of the pore structure, the authors derived in detail the governing equations of saturated mortars during freezing in the framework of the pore elasticity theory and analyzed the sensitivity of physical parameters to the influence of temperature stresses by means of stress-strain calculations. In addition, the effects of phase change and latent heat of freezing on the local thermodynamic equilibrium are considered, and a mathematical model is established for quantitatively simulating the temperature distribution of the specimen. This model is reformulated and extended in the current work to intuitively reveal the effect of concrete dimensions on the temperature hysteresis effect. The results of the numerical model calculations show that during the freezing process, for the specimen with dimensions of 50 mm × 50 mm × 50 mm and a water-cement ratio of 0.6, the maximum temperature difference from center to surface is 10 °C, the maximum vertical strain on the surface is 4.27 × 10^-4, and the maximum pore water pressure at the center of the specimen is 76 MPa. The model calculation results present a similar pattern to the physical interpretation and reference results, thus effectively evaluating the freezing damage process of saturated mortar.