非饱和混凝土中钢筋初锈时间的参数敏感性分析

Parametric Sensitivity Analysis of Corrosion Initiation Time for Reinforcing Bars in Unsaturated Concrete

摘要:

基于Fick第二定律和Darcy定律建立了氯离子扩散?对流耦合模型，并采用COMSOL Multiphysics软件进行数值求解。探明了每个干湿循环周期内氯离子含量和含水饱和度的变化规律，分析了钢筋初锈时间对各影响参数的敏感性。结果表明，扩散?对流耦合作用导致对流区和峰值氯离子含量的出现。随着暴露时间的增加，峰值氯离子含量明显增加。对流作用仅在混凝土浅层占据主导，氯离子在深层区的传输仍以扩散为主。钢筋初锈时间对临界氯离子含量的变化最为敏感，其次是保护层厚度、氯离子扩散系数、对流区深度和峰值氯离子含量。

Abstract:

A diffusion-convection governing equation for chloride transport was established based on the Fick’s second law and Darcy’s law. Variations of chloride profile and degree of water saturation during each wetting-drying cycle were obtained by using COMSOL Multiphysics software to numerically simulate the diffusion-convection process. Sensitivity of corrosion initiation time to different influencing factors was analyzed. The results indicate that the coupled effects of convection and diffusion lead to the existences of convection zone and peak chloride content. The peak chloride content significantly increases as the exposure duration increases. Convection effect only dominates the chloride transport in the shallow zone of concrete， the chloride transport in the deep zone is governed by diffusion. Corrosion initiation time is most sensitive to the variation of critical chloride content， followed by the concrete cover depth， chloride diffusion coefficient， convection zone depth and peak chloride content.