Deterioration of Concrete Structures Due to Chloride Corrosion and Preventive Measures

在海洋环境下，钢筋混凝土结构由于物理和化学侵蚀而劣化。钢筋的氯离子腐蚀是其劣化的主要机理。氯离子腐蚀速率受混凝土配合比、混凝土保护层厚度、钢筋和混凝土面层形式、环境条件等多种因素的影响（12 × 12 × 118 cm）的矿渣硅酸盐水泥（水灰比：W/C=0.40、0.60）、钢筋（变形钢筋（D10）：普通软钢。环氧树脂涂层、镀锌、铜钨）、合成树脂衬里（环氧树脂、乙烯基酯、聚氨酯）、覆盖混凝土深度（25、50 mm）。分别在日本海、内海和太平洋三个地点的飞溅区设置了三组梁，每年在这些区域对混凝土和钢筋的腐蚀进行非破坏性调查。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、碳化深度和抗弯试验。根据这些试验结果，对劣化机理进行了讨论。

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.