A Study on Limit State for Steel Corrosion of Concrete Members with Ground Granulated Blast-Furnace Slag

本研究的目的是测定磨细粒高炉矿渣混凝土的碳化速度和氯离子渗透速度，并研究碳化和盐害对钢筋锈蚀极限状态的影响。电子探针显微分析(EPMA)获得了氯离子的详细分布。在试验的基础上研制了钢筋锈蚀监测传感器。首先，对掺GGBFS的普通混凝土和高强混凝土进行了室内试验。高取代率、高细度和长时间湿固化提高了抗碳化和氯离子渗透的能力。高强混凝土的氯离子渗透在表层受到抑制，碳化深度和氯离子渗透深度几乎没有增加。只有掺有GGBFS的混凝土才能抵抗氯化钙等防冻剂的侵蚀。此外，GGBFS还可以延缓碳化和氯离子渗透、碳化和酸雨的联合劣化。其次，总结了钢的腐蚀极限状态和暴露试验结果的研究现状。发现氯离子浓度、风速、温度、温湿度偏差是控制混凝土锈蚀的重要因素，并通过实验验证了利用电子探针测量混凝土中氯离子分布的方法。EPMA法测定结果与常规滴定方法测定结果吻合较好。最后，对在实验基础上制成的传感器的实用性进行了检验。阐明了传感器钢丝腐蚀、电阻增大的情况，展望了传感器在结构中的实际应用前景。

The purpose of this study is to determine the carbonation speed and the penetration speed of chloride ion of concrete with ground granulated blast-furnace slag (GGBFS) and to investigate the effects of carbonation and salt damage to the limit state of steel corrosion. Electron probe micro analysis (EPMA) was performed to obtain the detailed distribution of chloride ion. A sensor to monitoring steel corrosion was made on an experimental basisFirstly, normal-strength and high-strength concrete with GGBFS were tested in laboratories. High replacement ratio, high fineness, and long wet curing increased resistance to carbonation and chloride ion penetration. Chloride ion penetration of high-strength concrete was restrained at surface layer, and carbonation depth and penetration depth of chloride ion hardly increased. Only the concrete with GGBFS could resist to an antifreezing agent such as calcium chloride. Moreover, GGBFS could delay combined deterioration of carbonation and chloride penetration, and of carbonation and acid rain.Secondly, past researches on the limit state of steel corrosion and the results of exposure tests were summarized. It was found that the important factors to dominate corrosion were concentration of chloride ion, wind velocity, temperature, the deviation of temperature and humidity.Then, a method using EPMA to obtain the detailed distribution of chloride ion in concrete was verified experimentally. The results by EPMA method well agreed with the results by usual titration method.Lastly, practicality of the sensor made on experimental basis was examined. The condition that the steel wire of sensor corroded and electric resistance of it increased was clarified, and there is prospect of a practical application of the sensor for structures.