Deterioration of Concrete Structures Due to Chloride Corrosion and Preventive Measures

在海洋环境下，钢筋混凝土结构受到物理和化学侵蚀而发生劣化。主要劣化机理是钢筋的氯化物腐蚀。氯化物腐蚀速率受混凝土配合比、混凝土覆盖深度、钢筋和混凝土表面衬砌类型、环境条件等多种因素的影响。钢筋混凝土梁（12X12x118cm）采用波特兰高炉矿渣水泥（水灰比：W/C=0.40, 0.60），钢筋(变形钢筋（D10）：普通低碳钢。环氧涂层、镀锌、铜钨)、合成树脂衬里（环氧树脂、乙烯酯、聚氨酯）、覆盖混凝土深度（25、50mm）。在日本海、内海和太平洋三个地方的飞溅区分别设置了三组梁。每年都对这些地区的混凝土和钢筋的腐蚀进行无损检测。在实验室对部分混凝土梁进行了脉冲速度、半电池电位、极化电阻、电位滴定、x射线衍射分析、碳化深度和弯曲试验。根据试验结果，讨论了劣化机理。

Under marine environment, the rein-forcrd concrete structure is deteriorated due to physical and chemical attacks. The main deterioration mechanism is the chloride corrosion of reinforcing steel. The rate of chloride corrosion is influenced by various factors such as mix proportion of concrete, dept of concrete cover, types of reinforcing steel and concrete surface lining, environmental condition and so on.The reinforced concrete beams (12X12x118cm) were prepared with portland blast-furnace slag cement (water cement ratio : W/C=0.40, 0.60), reinforcing steel (deformed bar (D10) : regular mild steel. Epoxy coated, galvanized, Cu-W), synthetic resin lining (epoxy, vinyl ester, polyurethane), depth of cover concrete (25, 50mm). Three series of beams were set at the splash zone of three places, the Sea of Japan, the Inland Sea and the Pacific, respectively.The corrosion of concrete and reinforcing steel was investigated nondestructively in these fields each year. Some of these concrete beams were tested using pulse velocity, half cell potential, polarization resistance, potentiometric titration, X-ray diffraction analysis, carbonation depth and flexural test in the laboratory. The deterioration mechanism is discussed based on the results of these tests.