沿海混凝土结构氯离子对流区深度计算模型

沿海干湿交替环境下的氯离子传输方式和影响机理等问题是混凝土耐久性研究的主要内容,描述混凝土内部氯离子传输行为的计算模型通常由偏微分方程组成,求解方法较为复杂。为了简单而相对精确地分析氯离子的传输过程,本文提出了计算修正Fick定律模型中对流区深度参数Δx的新途径,通过综合考虑混凝土细观尺度组成、环境温度场变化、水分迁移和氯离子传输等因素,建立起干湿交替区域氯离子传输的计算模型,依据该模型可以较为准确地得到Δx的数值,进而对不同服役环境中的氯离子传输展开分析,根据计算结果给出考虑服役时间、日平均气温和干燥湿润时间比等参数的对流区深度Δx时变公式。这些公式提高了预测干湿交替环境中氯离子传输的修正Fick定律模型的适用性与准确性,可为干湿交替环境中的混凝土结构耐久性设计提供了简单有效的计算方法。

Calculation Model for Depth of Chloride Ion Convection Zone in Coastal Concrete Structure

The chloride ion transport mode and influence mechanism in the coastal dry-wet alternate environment are the main contents of concrete durability research, which has attracted wide attention and discussion of scholars. The calculation model describing the chloride ion transport behavior in concrete is usually composed of partial differential equations, and the solution method is complex. To analyze the chloride ion transport process simply and accurately, this paper proposed a new way to calculate the depth parameter Δx in the modified Fick’s law model. The calculation model of chloride ion transport in the dry-wet alternate region was established by the meso-scale composition of concrete, the ambient temperature field, water migration and chloride ion transport. According to the model, the value of Δx can be accurately obtained. Then the chloride ion transport in different service environments was analyzed. According to the calculation results, the time-varying formula of convection zone depth Δx considering the service time, daily average temperature and drying-wetting time ratio was summarized in this paper. These formulas improve the applicability and accuracy of the modified Fick’s law model for predicting chloride ion transport and distribution in dry-wet alternate environment. The above results can provide a simple and effective calculation method for the durability design of concrete structures in dry-wet alternate environment.