杂散电流与氯盐作用下埋地混凝土中钢筋锈蚀研究

Study on corrosion of reinforcement in buried concrete under the action of stray current and chlorine salt

沿海地铁轨道钢筋混凝土结构因电流渗漏会处于杂散电流和氯离子共存环境中,导致轨道混凝土结构快速失效.本文在真实土壤中掺加1.5%氯盐构建盐渍土环境,采用10~30 V恒压直流电模拟杂散电流,研究钢筋混凝土在杂散电流与氯盐复合下的腐蚀损伤、锈蚀产物特性及其锈胀应力等.结果表明:混凝土中近保护层钢筋首先锈蚀、锈蚀面钢筋呈现部分点蚀并伴随有非均匀锈蚀现象,但随着腐蚀进行、钢筋上表面发生大面积锈蚀并向远保护层发展;钢筋锈蚀产物主要以亚铁氧化物为主、并伴随有氯化亚铁存在;钢筋锈蚀产生的膨胀应力大约在2~3 MPa;土壤氯离子含量增加、杂散电流密度增大会加速钢筋锈蚀和混凝土开裂,锈胀应力提高50%左右;杂散电流和氯离子共同作用下钢筋锈蚀程度远大于单一因素的影响.

The reinforced concrete structure of coastal subway track will be in the coexistence environment of stray current and chloride ions due to current leakage,which leads to the rapid failure of track concrete structure.In this paper,1.5%chloride salt is mixed with real soil to construct saline soil environment,and 10-30 V constant voltage DC is used to simulate stray currents to study the corrosion damage,corrosion product characteristics and its corrosion-induced expansive pressure of reinforced concrete under the compound of stray currents and chloride salt.The results indicate that the reinforcement near the protective layer in concrete first rusts,and the reinforcement on the rusted surface shows partial pitting corrosion accompanied by non-uniform corrosion.However,as the corrosion progresses,a large area of corrosion occurs on the upper surface of the reinforcement and develops towards the far protective layer.The corrosion products of reinforcement are mainly ferrous oxides,accompanied by ferrous chloride,and the expansion stress generated by the corrosion of reinforcement is about 2-3 MPa.The increase of soil chloride ion content and stray current density will accelerate the corrosion of reinforcement and concrete cracking,and the corrosion expansion stress will increase by about 50%.The corrosion degree of reinforcement under the combined action of stray current and chloride ions is much greater than that of a single factor.