The aim of this paper was to use the surface fractal dimension (D_s) to evaluate the chloride ion penetration of cement mortar in extremely cold regions. Pore structure is a critical factor that influences the permeability of cement mortar. This study investigated surface fractal dimensions of the pore structure of cement mortars, which were subject to one-time freezing for 7 days after casting. A thermodynamic model was applied to calculate D_s on the basis of mercury intrusion porosimetry data. The results show that the pore structures of all specimens exhibit the scale-dependent fractal property, and three distinct fractal regions (I, II, III) are obtained. According to the regression analysis results of fractal dimension and pore structure parameters, it was found that the fractal dimension can characterise the complexity and chaos of pore structure and predict pore size distribution. Based on this, a linear regression between chloride diffusion coefficient (D_nssm) and D_s in fractal regions was carried out. The results show that D_s of micro pores (region I) have good correlation with D_nssm, up to 0.92908, which is more accurate than the porosity. An index of surface fractal dimension is proposed to evaluate the durability of concrete buildings in extremely cold regions.

中文翻译：

---

评估寒冷环境中砂浆氯离子渗透的新方法

本文的目的是利用表面分形维数 ( D _s ) 来评估极寒地区水泥砂浆的氯离子渗透情况。孔隙结构是影响水泥砂浆渗透性的关键因素。本研究调查了水泥砂浆在浇注后一次冻结 7 天后孔隙结构的表面分形维数。应用热力学模型计算D _s基于压汞孔隙率数据。结果表明，所有样品的孔隙结构都表现出与尺度相关的分形特性，并获得了三个不同的分形区域（I、II、III）。根据分形维数和孔隙结构参数的回归分析结果发现，分形维数可以表征孔隙结构的复杂性和混沌性，预测孔径分布。在此基础上，进行了分形区域中氯离子扩散系数（D _nssm）与D _s之间的线性回归。结果表明，微孔（区域I）的D _s与D _nssm具有良好的相关性，高达 0.92908，比孔隙率更准确。提出了一种表面分形维数指标来评价极寒地区混凝土建筑的耐久性。