Deterioration of Concrete Structures Due to Chloride Corrosion and Preventive Measures

在海洋环境下，钢筋混凝土结构会受到物理和化学侵蚀而发生劣化。其劣化机理主要是钢筋的氯离子腐蚀。混凝土的氯离子腐蚀速率受混凝土配合比、混凝土保护层厚度、钢筋种类和混凝土表面衬砌、环境条件等多种因素的影响。采用硅酸盐矿渣水泥(水灰比：W/C=0.40、0.60)、钢筋(变形筋(D10)：普通软钢)制作钢筋混凝土梁(12X12×118 cm)。环氧涂层，镀锌，铜钨)，合成树脂衬里(环氧树脂，乙烯基酯，聚氨酯)，混凝土覆盖层深度(25，50 mm)。在日本海、内陆海和太平洋三个地方的飞溅区分别设置了三组梁，每年在这些地方无损地调查混凝土和钢筋的腐蚀情况。采用脉冲速度法、半电池电位法、极化电阻法、电位滴定法、X射线衍射法、碳化深度法、弯曲试验法对部分混凝土梁进行了测试。根据试验结果，对其劣化机理进行了探讨。

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.