冻融循环作用后钢筋混凝土电化学除氯效果研究

Study on Electrochemical Chloride Extraction effect of Reinforced Concrete after Freeze-thaw Cycle

为探究盐冻环境钢筋混凝土结构经电化学除氯后的残余氯离子分布规律,本文设计快速冻融试验,对冻融循环作用后的钢筋混凝土开展电化学除氯试验,研究冻融循环次数、除氯时间和粉煤灰掺量等因素对钢筋混凝土电化学除氯效果的影响。研究表明,粉煤灰混凝土电化学除氯效率受冻融循环作用影响和粉煤灰二次水化的共同影响,冻融循环作用引起的混凝土性能劣化导致电化学除氯后混凝土内残余氯离子呈凸型分布,集聚在距混凝土表面15~25 mm范围,钢筋附近残余氯离子含量最低。结果表明,冻融循环作用会引起混凝土电化学平均除氯效率上升,相较于未冻融试件,冻融循环作用100次的试件上升约12.5%;随电化学除氯时间增加,平均除氯效率会增大,混凝土内残余氯离子含量下降和外迁总量正相关;随粉煤灰掺量增加,混凝土电化学除氯效率增大,掺10%、20%、30%的粉煤灰混凝土,其28 d平均除氯效率分别达到51.2%、54.5%、59.9%。

In order to explore the distribution of residual chloride ions in reinforced concrete structures after electrochemical chlorine removal in the salt-frozen environment,a rapid freeze-thaw test was designed and electrochemical chloride extraction tests of reinforced concrete after freeze-thaw cycles were carried out.The influence of freeze-thaw cycles,chlorination time and fly ash content on the electrochemical chloride extraction of the reinforced concrete was studied.Studies showed that the electrochemical chloride extraction efficiency of fly ash concrete can be affected by the combined impact of the freeze-thaw action and secondary hydration of fly ash.The deterioration of concrete performance caused by freeze-thaw cycle can lead to the convex distribution of residual chloride ions in concrete after electrochemical chloride extraction.After electrochemical chlorine removal,the residual chloride ions in concrete present a convex distribution trend and gathered in the depth of 15-25 mm from the concrete surface.And the content of residual chloride ions near the reinforcement bar is the lowest.The results show that the freeze-thaw action leads to the increase of average dechlorination efficiency of concrete.Compared with the specimens without freeze-thaw attacking,the average dechlorination efficiency of concrete after 100 freeze-thaw cycles increases by about 12.5%.With the electrochemical chlorine removal time increasing,the average chlorine removal efficiency increases,and the decrease of residual chlorine ions content in concrete is positively correlated with the total amount of external migration.With the fly ash content increasing,the dechlorination efficiency of concrete increases.The28-day average dechlorination efficiency with fly ash content of 10%,20%and 30%can reach51.2%,54.5%and 59.9%,respectively.