孔隙分形修正的混凝土中氯离子扩散系数
Chloride diffusion coefficient modified by pore fractal theory in concrete

在已有的氯离子扩散理论和孔隙分形理论的基础上，提出小孔的孔轴线分形维数表征氯离子扩散的曲折度、大孔的孔表面分形维数修正孔隙率，并推导得到基于孔隙分形修正的氯离子扩散系数模型。通过分析龄期为14 d和28 d不同配比混凝土的基于孔隙分形的氯离子扩散系数模型的计算结果和快速氯离子扩散试验(ASTM C1202)电通量，发现两者之间有良好的线性关系。采用基于孔隙分形修正的氯离子扩散系数代入Fick第二定律的解析解，对试验后各组混凝土中不同扩散深度的氯离子浓度进行拟合，计算结果与实测值吻合情况较好。
Based on the theory of chloride diffusion and pore fractal theory a new model is proposed on the base that the sinuosity of chloride diffusion characterized by the axis fractal dimension of the small pore and the porosity of concrete modified by the surface fractal dimension of large pore. The model was applied to analyze 14 d and 28 d age concrete with different proportions and the results, showed a linear relationship with those of he Coulomb electric charge determined by The Rapid Chloride Permeability Test (RCPT)—American Society of Testing and Materials (ASTM) test method C1202. The Chloride diffusion coefficient modified by pore fractal theory was presented in this study. Two different chloride concentrations in different depths of concrete were calculated by modified Chloride diffusion coefficient and orthodox Chloride diffusion coefficient. The comparison between two different Chloride diffusion coefficient indicated that the chloride concentration calculated by modified Chloride diffusion coefficient agreed better with the measured chloride concentration.