Relationships between and cracking and corrosion of steel in concrete structure

试验一：用电化学和电学方法研究了保护层厚度、水灰比和浇注方向对混凝土中钢筋宏电池腐蚀的影响。将埋入1%氯离子污染混凝土中的钢(阳极)与埋入氯离子污染混凝土中的不锈钢板(阴极)电连接。将试件在3.27%的氯化钠溶液中浸泡1天，在自然环境中干燥1天，发现：1)阳极钢保护层厚度对氯离子污染混凝土中钢阳极的宏孔腐蚀程度有影响，2)水灰比对腐蚀有显著影响，3)由于混凝土的渗水，水平浇筑的混凝土中钢筋的腐蚀明显高于垂直浇筑的混凝土。试验2：用加速…研究了保护层厚度、裂缝、水灰比和浇注方向对混凝土中钢的宏孔腐蚀的影响多采用钢筋混凝土梁试件进行锈蚀试验。为了测量宏电池的腐蚀电流，在增强钢上涂上了环氧树脂膜，中间只剩下27 mm的区域(阳极)没有保护。钢与设置在钢附近的不锈钢棒(阴极)电连接(图1)。加载梁试件，引入规定宽度的裂缝，在65ﾟC、3.2%氯化钠溶液中浸湿一天，在室温下干燥一天，重复35次。对其电化学性能和腐蚀性能进行了测试。结果表明：1)电化学性质与腐蚀电流的变化相吻合，可以无损地判断混凝土中钢筋的腐蚀情况。极化电阻倒数的积分与腐蚀程度有关。2)保护层厚度越大，裂缝宽度越窄，腐蚀程度越小。3)低水灰比混凝土对腐蚀有明显的抑制作用。保护层对60%W/C混凝土的锈蚀影响较大，40%W/C混凝土的裂缝影响较大。4)混凝土浇筑方向对钢筋锈蚀影响不大。较少

Experiment 1: The effects of cover thickness, water cement ratio and casting direction on macrocell corrosion of steel in concrete was investigated by electrochemical and electrical methods. Steel (anode) embedded in 1% Cl^- contaminated concrete was electrically connected to stainless steel plate (cathod) embedded in Cl^- contaminated concrete. The specimens were subjected to repeated cycles of one day wetting in 3.27 %NaCl solution and one day drying in natural environment.It was found that : 1) cover thickness over anode steel has effects on the macrocell corrosion degree of steel anode in Cl^- contaminated concrete, 2) water cement ratio considerably influenced corrosion, 3) corrosion of steel in concrete cast horizontally was remarkably higher than that in concrete cast vertically due to bleeding of concrete.Experiment 2: The effects of cover thickness, cracking, water cement ratio and casting direction on macrocell corrosion of steel in concrete was investigated by a accelerated … More corrosion test using reinforced concrete beam specimens. In order tomeasure macrocell corrosion currents, reinforcing steels were coated with epoxy resin films, leaving only 27 mm zone (anode) in the center unprotected. The steel was connected electrically to stainless bars (cathod) set near the steel (Fig.1). Beam specimens were loaded to introduce cracks of defined width and subjected to 35 repeated cycles of one day wetting in 65 ﾟC, 3.2 % NaCl solution and one day drying under room environment. The electrochemical characteristics and corrosion deteriora lion were also measured. It was found that : 1) The electrochemical characteristics coincided with change of corrosion currents, and it is possible to judge undestructively the condition of corrosionof steel in concrete. The integration of the reciprocal of polarization resistance related to the degree of corrosion.2) As cover thickness was large and crack width was narrow, the degree of corrosion decrease.3) Low water cement ratio concrete inhibited remarkably corrosion. Effects of cover on corrosion was large in w/c 60 % concrete and effects of crack was large in w/c 40 % concrete.4) The casting direction of concrete had not effect on corrosion of steel. Less