修正的氯离子在混凝土中的扩散模型及其工程应用

通过参数定义对Fick定律的假定进行修正,推导氯离子在混凝土中扩散的多因素修正模型,综合考虑氯离子扩散系数的时随效应、混凝土的氯离子结合能力和混凝土自身缺陷对扩散过程的影响.经分析试算,给出模型中参数的取值.利用修正的扩散模型,推导定值法、基于概率性能和基于时变可靠度的混凝土结构工作寿命预测方法,并采用上述方法对一在建的实际工程进行寿命预测.结果表明,基于时变可靠度的预测方法不仅可以考虑氯离子扩散系数及混凝土保护层厚度的随机特性,而且可以方便地考虑环境变量的随机特性,通过调整目标可靠度得到的预测结果与定值法和基于概率性能的预测方法的结果相吻合.

Corrected diffusion model of chloride in concrete and its engineering application

A multi factor diffusion model of chloride in concrete was formulated, in which the hypothesis of Fick’s law was corrected through parameter definition, and the factors of time dependence of chloride diffusion coefficient, chloride binding capacity of concrete, and self defects of concrete were taken into account. The values of the parameters in the model were given for practical applications according to the pilot calculation and analysis of mass data. By using this diffusion model, three calculation methods of concrete structure service life were further deduced, including definite value method, probability performance based method and time dependent reliability based method. The service life prediction for an actual project being constructed was carried out by using various prediction approaches mentioned above. The results show that the time dependent reliability based method can consider the randomness of chloride diffusion coefficient and the depth of concrete covering layer, and the stochastic characteristic of environment variable can be easily taken into account. By adjusting target reliability, the prediction results are consistent with those of the other two methods.