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多因素作用下杂散电流对离子迁移影响研究

Study on the Influence of Stray Current on Ion Migration Under Multi-factors

  • 摘要: 本研究旨在探究电场作用下氯离子和硫酸根离子的迁移规律,评估多因素耦合作用下杂散电流对混凝土劣化进程的影响。通过多因素耦合试验,施加0 V~40 V直流电于内置钢筋的混凝土试件,并将其分别置于3% NaCl溶液和3% NaCl+1%Na2SO4混合溶液中,采用离子色谱和扫描电镜获取离子浓度分布和水化产物微观结构。结果显示,杂散电流显著加速离子迁移,电压越高,氯离子和硫酸根离子的侵入深度与浓度越大,电压为40 V时,25 mm~30 mm深度范围内,单盐体系中氯离子含量为0.395%,混合盐体系中氯离子含量和硫酸根离子含量分别为0.195%和0.2030%;硫酸盐反应产物填充孔隙,改变混凝土微观结构,进而抑制氯离子渗透,同深度氯离子浓度最大降低幅度可达87%。研究表明,电迁移是离子加速侵入的主因;硫酸根离子反应具有双重效应,混凝土先密实后破坏;杂散电流缩短硫酸盐侵蚀各阶段时间,加剧混凝土耐久性劣化。

     

    Abstract: The purpose of this study is to explore the migration law of chloride ions and sulfate ions under the action of electric field, and to evaluate the influence of stray current on the deterioration process of concrete under the coupling of multiple factors. Through multi-factor coupling test, 0 V~40 V direct current was applied to the concrete specimens with built-in steel bars, and they were placed in 3% NaCl solution and 3% NaCl+1% Na2SO4 mixed solution, respectively. Ion concentration distribution and microstructure of hydration products were obtained by ion chromatography and scanning electron microscopy. The results show that the stray current significantly accelerates ion migration. The higher the voltage, the greater the penetration depth and concentration of chloride ions and sulfate ions. When the voltage is 40 V, in the depth range of 25 mm~30 mm, the chloride ion content in the single salt system is 0.395%, and the chloride ion content and sulfate ion content in the mixed salt system are 0.195% and 0.2030%, respectively. The sulfate reaction product fills the pores and changes the microstructure of the concrete, thereby inhibiting the penetration of chloride ions, and the maximum decrease of chloride ion concentration at the same depth can reach 87%. Studies have shown that electromigration is the main cause of accelerated ion intrusion; the sulfate ion reaction has a double effect, and the concrete is compacted first and then destroyed. The stray current shortens the time of each stage of sulfate attack and aggravates the deterioration of concrete durability.

     

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