矿物掺合料高性能混凝土氯离子扩散特性研究

为研究沿海地区高性能混凝土桩基础的耐久性，采用干湿循环浸泡法对18个高性能混凝土试件进行了氯盐侵蚀试验，分析了高性能混凝土的氯离子浓度分布，得到了高性能混凝土的表面氯离子浓度、氯离子扩散系数的时变方程。在此基础上进行了高性能混凝土氯盐侵蚀的数值模拟，分析了钢筋直径（20、28 mm和36 mm）和保护层厚度（20、30、40 mm和50 mm）对沿海地区高性能混凝土桩基础氯离子浓度分布和氯离子扩散系数的影响，提出了相应的耐久性设计建议。研究结果表明:高性能混凝土毛细管吸附区与氯离子扩散区的位置在0~5 mm之间，高性能混凝土的最大稳定深度为50 mm；随着时间的增长，高性能混凝土氯离子扩散系数逐渐降低，氯离子浓度增长速率拐点为25 mm；相较氯盐侵蚀溶液浓度，氯离子扩散系数与氯盐侵蚀时间的关系更大。结合钢筋的临界氯离子浓度正态分布，建议沿海地区输电工程高性能混凝土桩基础的保护层厚度为70 mm。

Study on chloride diffusion in high performance concrete with mineral admixtures

To study the durability of the pile foundation of high performance concrete in coastal areas, the chloride erosion tests were carried out on 18 high performance concrete specimens by wet-dry cycle soaking method. The chloride ion concentration distribution of high performance concrete was analyzed. And the time-varying equations of surface chloride ion concentration and chloride ion diffusion coefficient of high performance concrete were obtained. Based on this, the numerical simulation of chloride erosion of high performance concrete was carried out. The influence of diameter of steel bar (20, 28, and 36 mm) and protective layer thickness (20, 30, 40, and 50 mm) on the chloride ion concentration and chloride ion diffusion coefficient of high performance concrete pile foundation in coastal areas was analyzed and the corresponding durability design suggestions was put forward. The results show that the positions of capillary adsorption zone and chloride ion diffusion zone of high performance concrete are between 0-5 mm. The maximum stable depth of high performance concrete is 50mm. With the increase of time, the chloride ion diffusion coefficient of high performance concrete decreases, and the inflection point of growth rate of chloride ion concentration is 25 mm. Compared with the concentration of the chlorine-eroded solution, the time of chlorine-eroded solution has more influence on the diffusion coefficient of chloride ion. Considering the normal distribution of the critical chloride ion concentration of reinforcements, the thickness of the protective layer of high performance concrete pile foundation for power transmission projects in coastal areas should be 70 mm.