Abstract This study aims to obtain insights into the retardation mechanism of citric acid in an ettringite-based binder from ladle slag and gypsum. The hydration kinetics and phase assemblage of the binder were experimentally investigated and thermodynamically modelled. Additionally, the effects of citric acid on synthetic ettringite were studied to obtain further understanding of the interaction between this organic ligand and the crystal. Experimental results reveal that citric acid works as an inhibitor of ettringite's formation leading to the precipitation of monosulfate and gypsum; the ettringite surface blockage by citrate ligand effectively prevents precipitation of this crystal. This leads to an overestimation in the precipitation of ettringite in the thermodynamic model due to this kinetic barrier imposed by the ligand. Thermodynamic modelling suggests ettringite, monosulfate, aluminum hydroxide, and stratlingite as main hydrates in this binder, whereas an intermixed C–(A–)S–H gel was observed experimentally instead of stratlingite.

中文翻译：

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柠檬酸在钙矾石基粘合剂中的阻滞机理

摘要 本研究旨在深入了解柠檬酸在来自钢包渣和石膏的钙矾石基粘合剂中的缓凝机制。对粘合剂的水合动力学和相组合进行了实验研究和热力学建模。此外，还研究了柠檬酸对合成钙矾石的影响，以进一步了解这种有机配体与晶体之间的相互作用。实验结果表明，柠檬酸可作为钙矾石形成的抑制剂，导致单硫酸盐和石膏的沉淀；柠檬酸盐配体对钙矾石表面的阻塞有效地防止了该晶体的沉淀。由于配体施加的这种动力学障碍，这导致高估了热力学模型中钙矾石的沉淀。