This paper reviews the formation and breakdown of passive film on the surface of reinforcement steel in alkali-activated materials (AAMs) considering the characteristics of reaction product and pore solution chemistry. The literature review shows that the pore solution of AAMs has higher concentrations of OH−, Na+, silica and aluminium compared to Portland cement (PC). This relatively high alkalinity contributes to the generation of a passive film, which has positive effects on the corrosion resistance of reinforcement steel embedded in AAMs. The silica-aluminium zeolite layer present on the surface of passive film adsorbs chloride ions and effectively inhibits chloride-induced depassivation. Generally, lower ratios of [Cl−]/[SO42−] and [Cl−]/[S2O32−] potentially inhibit the depassivation of reinforcement steel. The high pH value and the elevated concentrations of HS− of AAMs contribute to the increase of critical chloride content (Ccrit). However, the higher content of reduced sulfide mainly dissolved from slag results in the consumption of dissolved oxygen, which is necessary for the formation of passive film. Generally, the presence of reduced sulfide forms Fe-S complexes on the surface of reinforcement steel in AAMs. Even so, higher corrosion resistance for AAMs is mostly expected with longer depassivation time due to finer microstructure and lower chloride penetration rates compared to PC-based materials. The decrease in pH value in the pore solution of the AAMs is the main factor affecting carbonation-induced depassivation of reinforcement steel, while high concentrations of bicarbonate and carbonate ions inhibit depassivation.

中文翻译：

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碱活化材料中增强钢的钝化和去钝化——研究进展


本文从反应产物和孔隙溶液化学特性的角度，综述了碱性活化材料 （AAMs） 中增强钢表面钝化膜的形成和破坏。文献综述表明，与波特兰水泥 （PC） 相比，AAMs 的孔隙溶液中含有更高浓度的 OH−、Na+、二氧化硅和铝。这种相对较高的碱度有助于钝化膜的产生，这对嵌入 AAM 中的增强钢的耐腐蚀性有积极影响。存在于钝化膜表面的二氧化硅铝沸石层吸附氯离子并有效抑制氯化物诱导的钝化。通常，较低的 [Cl−]/[SO42−] 和 [Cl−]/[S2O32−] 比例可能会抑制增强钢的钝化。AAM 的高 pH 值和高浓度的 HS− 会导致临界氯化物含量 （Ccrit） 的增加。然而，主要从炉渣中溶解的还原硫化物含量较高会导致溶解氧的消耗，这是形成钝化膜所必需的。通常，还原硫化物的存在会在 AAM 中的增强钢表面形成 Fe-S 络合物。即便如此，与 PC 基材料相比，由于微观结构更精细，氯化物渗透率更低，因此大多数情况下预计 AAM 的耐腐蚀性更高，脱钝时间更长。AAMs 孔隙溶液中 pH 值的降低是影响碳化诱导钢筋脱钝化的主要因素，而高浓度的碳酸氢根和碳酸根离子抑制了硼化脱钝化。