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基于Fick第二扩散定律,综合考虑了混凝土初始表面氯离子浓度以线性方式变化、扩散系数随时间不断减小以及温湿度对氯离子扩散的影响,把氯离子扩散过程分为两个阶段,推导得到一个新的氯离子扩散方程,结合现有数据,对理论数学模型进行了验证。结果表明:随着表面氯离子浓度以线性积累速率的减慢,短期内氯离子扩散过程也变得缓慢;阶段一与阶段二时间结合点处的两个氯离子曲线分布得到很好的吻合,用新方程所得到的氯离子分布曲线与以往普遍采用基准方程得到的分布曲线也能很好地匹配,在分别计算10 a,25 a,50 a混凝土中钢筋表面氯离子浓度到达锈蚀临界浓度时,用新方程比采用基准方程时要提前约3%~14%,且随着时间的增长二者之间差异不断减小。
Based on Fick’s second law of diffusion, the chloride ion diffusion process is divided into two stages based on Fick’s second law of diffusion, considering the linear change of chloride ion concentration on the initial surface of concrete, the decreasing of diffusion coefficient with time, and the influence of temperature and humidity on the chloride ion diffusion. Get a new chloride ion diffusion equation, combined with the existing data, the theoretical mathematical model was verified. The results show that the chloride ion diffusion process becomes slow in the short term as the surface chloride ion concentration slows down linearly. The distribution of the two chloride ions at the junction of stage 1 and stage 2 is in good agreement. The chloride ion distribution curve obtained by the new equation can also be well matched with the distribution curve obtained by the conventional reference equation. When the chloride ion concentration on the steel surface reaches the critical corrosion concentration in 10 a, 25 a and 50 a respectively , With the new equation than using the baseline equation to advance about 3% to 14%, and with the increasing difference between the two continue to decline.