Limestone calcined clay cement (LC3), a low-carbon cementitious material, has demonstrated outstanding resistance to chloride ion penetration. However, the real environment is rich in many harmful ions beyond chloride ions, including sulfate and magnesium ions, making the interactions among these ions highly complex. This study systematically explores the impact of sulfate ions and the synergistic effects of sulfate and magnesium ions on the chloride ion transport properties and chloride ions binding capacity of LC3. The characteristics of phase assemblage, pore structure, and microstructure vary differently under different environments. Furthermore, a thermodynamic model was employed to determine the impact of ion concentration and type on the phase assemblage. The findings suggest that within LC3, sulfate ions significantly affect Friedel's salt stability, converting it into ettringite (Ett). In addition, sulfate ions can combine with monosulfate (Ms) or undergo ion exchange with hemicarboaluminate (Hc)/monocarboaluminate (Mc) to form Ett, refining the pore structure and reducing the diffusion coefficient of chloride ions. However, prolonged exposure leads to sample expansion, accelerating the diffusion rate of chloride ions. Furthermore, the duration of sulfate ion inhibition on chloride diffusion is associated with the content of calcium aluminate phases. The combined attack of sulfate and magnesium ions lead to C-(A)-S-H decalcification, generation of gypsum and brucite, and decomposition of Friedel's salt and Ett, which further degrades matrix and promotes chloride ion diffusion. However, reducing the clinker amount in LC3 effectively enhances chloride binding capacity and reduces gypsum and brucite formation.

中文翻译：

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深入了解硫酸根离子和镁离子对石灰石煅烧粘土水泥中氯化物扩散和相组合的机制 （LC3）

石灰石煅烧粘土水泥 （LC3） 是一种低碳胶凝材料，已表现出出色的抗氯离子渗透性。然而，除了氯离子之外，实际环境中还富含许多有害离子，包括硫酸根离子和镁离子，这使得这些离子之间的相互作用非常复杂。本研究系统探讨了硫酸根离子的影响以及硫酸根离子和镁离子对 LC3 氯离子传输特性和氯离子结合能力的协同作用。在不同环境下，相组合、孔隙结构和微观结构的特性不同。此外，采用热力学模型来确定离子浓度和类型对相组合的影响。研究结果表明，在 LC3 中，硫酸根离子显着影响 Friedel 盐的稳定性，将其转化为钙矾石 （Ett）。此外，硫酸根离子可与一硫酸盐 （Ms） 结合或与半碳铝酸盐 （Hc）/一碳铝酸盐 （Mc） 进行离子交换以形成 Ett，细化孔隙结构并降低氯离子的扩散系数。然而，长时间暴露会导致样品膨胀，从而加速氯离子的扩散速率。此外，硫酸根离子对氯离子扩散的抑制持续时间与铝酸钙相的含量有关。硫酸根离子和镁离子的共同作用导致 C-（A）-S-H 脱钙，生成石膏和水镁石，以及 Friedel 盐和 Ett 的分解，从而进一步降解基质并促进氯离子扩散。然而，减少 LC3 中的熟料用量可有效提高氯化物结合能力并减少石膏和水镁石的形成。