杂散电流对地下结构混凝土中氯离子传输过程的影响

Influence of stray current on chloride ion transport mechanism in underground structure concrete

为了研究杂散电流对地下结构混凝土中氯离子传输性能的影响,进行了四种不同杂散电流强度下C55双掺(粉煤灰和矿渣)混凝土试件在氯盐溶液中的腐蚀试验。结果表明:存在杂散电流情况下,混凝土内氯离子传输以电迁移为主,且不均匀电场中侵入氯离子浓度分布与电场强度分布相关;杂散电流强度越大,侵入混凝土中的氯离子含量越多,氯离子含量越高,反应生成了更多的Friedel盐;杂散电流能够显著降低水泥材料对氯离子的结合能力,其作用在于削弱了混凝土对氯离子的物理吸附作用,使得部分结合状态的氯离子转变为自由氯离子。

To investigate the impact of stray current on the transport mechanism of chloride ion in underground structure concrete, four levels of stray current was applied to the corrosion tests of C55 double - mixture concrete （ fly ash and slag ） in chloride solution. The tests results show that, with the existence of stray current, the transport of chloride ion is charged by the electromigration and the concentration of chloride ion is affected by the intensity of the electric field under a nonuniform electric field.With the increase in stray current strength, more chloride ions immigrate into concrete that results in a high concentration of chloride and more production of Friedel＇s salt. The stray current can remarkably bring down the binding capacity of cementitious materials to the chloride ions. This is due to the physical adsorption of concrete to chloride is weakened and part of bounded chloride ions turn into free chlorine ions.