非饱和状态下氯离子在混凝土中的渗透机理及计算模型

MECHANISM AND MATHEMATIC MODELING OF CHLORIDE PERMEATION IN CONCRETE UNDER UNSATURATED STATE

在氯盐侵蚀环境中,干湿交替区域对应有害介质侵蚀最为严重的结构部位是结构耐久性设计的关键。考虑水分扩散系数与孔隙中水分饱和度的非线性函数关系以及水分蒸发的迟滞效应,建立了水分在混凝土中的非线性扩散模型,并在此基础上建立了氯离子在非饱和条件下的对流扩散模型。用Crank-Nicolson方式建立了上述模型的差分格式,并通过参数敏感性分析确定了3个重要模型参数(湿润与干燥循环的时间比、混凝土孔隙初始的饱和度以及干燥过程中外界环境作用下表层混凝土的饱和度)对氯离子在非饱和条件下的对流扩散的影响。试验结果表明上述模型和试验检测结果之间具有良好的相关性。

In chloride containing environment, dry-wet cycling zones in concrete structures are always at the highest risk of corrosion. The hysteresis effect in evaporation of pore solution and the nonlinear relationship between diffusivity of moisture and saturation of pore are taken into consideration in modeling the transportation of moisture. And the chloride penetration model is completed based on the transportation model of moisture. Crank-Nicolson method is engaged to develop the finite difference format of the models above, and the influence of three main parameters, including the time proportion of dry and wet process, the initial saturation of pores and the saturation of pores near the surface of concrete during dry process, on the model is explored by sensitivity analysis. The resuits of proving experiment reveal that the results of model calculation have a good correlation with the measured results.