Layered double hydroxides (LDHs) have gained attention in the concrete research field, appearing as prospective additives for controlling chloride attack, and as micro or nano deliverers of corrosion inhibitors. This work reports the effect of ZnAl-NO2 LDH on the evolution of chloride concentration in the pore solution and on the corrosion resistance of iron in mortar samples exposed to 3.5 % NaCl solution. To this end, Ag/AgCl sensors were used to monitor the ingress of chloride ions into mortar, while the electrochemical state of the iron was evaluated by electrochemical impedance spectroscopy. Furthermore, the mortars were analyzed by XRD and TGA, and the total amount of chloride was measured with a commercial sensor. Mortars with LDH showed a slower increase of chloride ions in the pore solution and the preservation of the passive state of the Fe. The presence of LDHs did not cause a significant structural change in the mortars, which was evidenced by the similar distribution of the high frequency resistance as a function of depth in the samples with and without the additive. Finally, the amount of bound chloride in the cementitious material was higher in the LDH-containing mortars. In conclusion, ZnAl-NO2 LDH exhibited a positive effect on the protection of reinforcement embedded in mortar samples when subjected to chloride ingress.

中文翻译：

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ZnAl-NO2 LDH 对砂浆样品中氯离子截留和铁增强材料保护的影响


层状双氢氧化物（LDH）在混凝土研究领域引起了人们的关注，作为控制氯化物侵蚀的潜在添加剂以及作为腐蚀抑制剂的微米或纳米传递剂出现。这项工作报告了 ZnAl-NO2 LDH 对孔隙溶液中氯化物浓度的演变以及对暴露于 3.5% NaCl 溶液的砂浆样品中铁的耐腐蚀性的影响。为此，使用Ag/AgCl传感器来监测氯离子进入砂浆的情况，同时通过电化学阻抗谱评估铁的电化学状态。此外，通过XRD和TGA对砂浆进行了分析，并使用市售传感器测量了氯化物的总量。含有 LDH 的砂浆显示出孔隙溶液中氯离子的增加较慢，并且 Fe 的钝态得以保留。 LDH 的存在不会导致砂浆发生显着的结构变化，有和没有添加剂的样品中高频电阻随深度的相似分布就证明了这一点。最后，在含有 LDH 的砂浆中，胶凝材料中的结合氯含量较高。总之，当受到氯化物侵入时，ZnAl-NO2 LDH 对砂浆样品中嵌入的钢筋的保护具有积极作用。