氯盐和硫酸盐侵蚀下水泥净浆中钢筋锈蚀过程

针对氯盐和硫酸盐耦合作用下钢筋混凝土的腐蚀问题,设计制作了含水泥净浆保护层的水泥净浆-钢筋试件,测试了试件在氯盐和硫酸盐腐蚀溶液中的电化学阻抗谱(EIS),并分析了溶液类型、水灰比及水泥净浆保护层厚度对试件电化学参数及钢筋锈蚀程度的影响.结果表明:同单一氯盐溶液中的试件相比,在硫酸盐-氯盐复合溶液腐蚀前期,试件内钢筋表面电荷转移电阻较大,腐蚀电流密度较小,此时硫酸盐减缓了水泥净浆内钢筋的锈蚀进程;在硫酸盐-氯盐复合溶液腐蚀后期,试件内钢筋表面电荷转移电阻显著减小,腐蚀电流密度明显增加,此时硫酸盐加速了水泥净浆中钢筋的锈蚀进程.此外,试件中水泥净浆水灰比越大,钢筋锈蚀程度也越大,当水泥净浆保护层厚度增加时,钢筋锈蚀程度降低.

Corrosion Process of Steel Bar in Cement Pastes under Combined Action of Chloride and Sulfate Attacks

According to the corrosion of reinforced concrete under the combined action of chloride and sulfate attacks, some specimens of steel bar covered with cement paste layer were prepared to carry out the measurement of electrochemical impedance spectroscopy(EIS) on them immersed into chloride and sulfate solutions, and the influences of corrosion solution, water cement ratio, thickness of cement paste layer on their electrochemical parameters and the corrosion degree were analyzed. Results show that at the early period of corrosion, the surface charge transfer resistance of steel bar immersed into the combined chloride and sulfate solution is higher and the corrosion current density is lower than that in a chloride solution, so the additional sulfate in chloride solution can slow down the early corrosion process of steel bar in cement paste. But at the later period of corrosion, the surface charge transfer resistance of steel bar has an notable decrease, and the corrosion current density has a great increase, thus the additional sulfate can accelerate the later corrosion process of steel bar in cement paste. Additionally, the corrosion degree of steel bar in cement paste with high water cement ratio is higher than that with low water cement ratio, and it decreases with the increase of the thickness of cement paste layer.