干湿交替作用下氯离子在开裂混凝土中的输运规律

Chloride transport in cracked concrete under wet-dry cycling condition

为了获得干湿交替作用下氯离子在开裂混凝土内的侵蚀规律,采用双重孔隙介质模型,考虑氯离子在混凝土孔隙内的线性结合,将水分和氯离子在混凝土和裂缝内的迁移分别表示为扩散形式和对流-扩散形式,得出不同饱和度下的水分扩散方程和氯离子对流-扩散方程,以及Rayleigh-Ritz分布下相应的水分扩散系数随孔隙饱和度的变化规律,并采用有限单元法计算干湿交替作用下的水分和氯离子在一规则开裂混凝土内的迁移过程,得出的干燥与湿润过程中的氯离子侵蚀结果与试验结果较吻合。模拟结果表明:在干湿交替作用下,裂缝深度对超出裂缝部分的氯离子影响较大,而裂缝宽度、循环周期、初始饱和度对混凝土和裂缝中的氯离子浓度影响较小。

A model was established to predict the chloride transporting phenomena in the cracked concrete under wet-dry cycling condition. Dual porous medium model was adopted to represent the mediums of concrete and crack. Water and chloride ions migrations in the sound concrete and the crack under unsaturated condition were analyzed considering the linear binding of chloride in the concrete. In this model, water migration was expressed as diffusion mode and chloride transport was expressed as diffusion and advection mode. Diffusion coefficients of water and chloride under unsaturated condition were different and were gotten for the crack and the sound concrete using the Rayleigh-Ritz distribution. The finite element method was used to simulate the water and chloride migrations in a cracked concrete under wet-dry cycling condition. The simulation results agree well with the test results, indicating that the crack depth has a significant effect on chloride profiles beyond the crack tip. However, crack width, wet-dry cycle and initial saturation have little influence on the ingression of chloride ions in concrete and crack.