利用丝束电极技术研究氧浓度对海水海砂砂浆中钢筋锈蚀的影响

为探明氧浓度对海水海砂砂浆中钢筋锈蚀的影响,采用丝束电极技术,研究不同氧浓度(5%、21%、85%,体积分数)和水胶比(0.48、0.18)的海水海砂砂浆中电极表面腐蚀电位分布与电化学阻抗谱的时变规律。结果表明,丝束电极的极化电阻随腐蚀龄期的增加而降低,腐蚀电流密度随腐蚀龄期的增加而增加,且水胶比越大、氧浓度越高,两者的变化幅度越大。根据测试结果可判断,钢筋腐蚀的概率随氧浓度的增加而增大:较低的氧浓度(5%)可大大延缓钢筋由氯离子引发的脱钝行为,从而有效抑制钢筋腐蚀;而在高氧环境下,砂浆中钢筋的锈蚀是一个由局部到全面逐步氧化的非均匀锈蚀过程。减小水胶比可有效提高海水海砂水泥基体系中钢筋的耐腐蚀能力。

Influence of Oxygen Concentration on Reinforcement Corrosion in Seawater Sea-Sand Mortar Based onWire Beam Electrode Technique

To find out the influence of oxygen concentration on reinforcement corrosion in seawater sea-sand mortar, the wire beam electrode (WBE) technique was introduced. The influences of oxygen concentration (5%, 21%, 85%, volume fraction) and water-binder ratio (W/B) (0.48, 0.18) on time-dependent behavior of corrosion potential and electrochemical impedance spectroscopy (EIS) of WBE were separately investigated. Results show that the polarization resistance of WBE decreases and corrosion current density increases with the increase of corrosion time. The changes are greater with the increase of oxygen concentration and W/B.It can be observed from the experimental results that the corrosion probability of reinforcement increases with the increase of oxygen concentration. At a low oxygen concentration (5%), the reinforcement depassivation induced by chloride can be effectively retarded and thus the reinforcement corrosion is restrained. While at a high oxygen concentration, the reinforcement experiences a nonuniform corrosion process with progressive oxygenation from part to the whole. The anticorrosion capacity of reinforcement in seawater sea-sand cement-based systems can be effectively improved by decreasing W/B.