The mechanisms responsible for the compromised or lost dispersing capability of polycarboxylate ether (PCE) superplasticizers in two-part alkali-activated slag (AAS) have been extensively studied, but limited scientific understanding is available on how PCEs function or lose their dispersing efficiency in one-part AAS systems, particularly those prepared using greener carbonate -based solid activators. This study investigates the dispersing and adsorption behaviors of phosphate-based PCE in one-part AAS activated by K2CO3 or a combination of K2CO3 and CaO. Our findings indicate that in K2CO3-activated slag systems, the loss of phosphate-based PCE efficiency primarily results from the conformational contraction of PCE molecules, which deteriorates steric repulsion in the alkaline activating solution, rather than the insolubility of PCEs in alkaline solution or competitive adsorption between PCEs and carbonate anions on dissolving slag grains. In K2CO3-CaO-activated slag systems, when PCE dosage is below 5 mg/g, the consumption of PCE by early precipitates (e.g., C-A-S-H, gaylussite, calcite) contributes substantially to its lost efficiency; however, once the PCE dosage surpasses this threshold, the dominant factor influencing PCE efficiency shifts to the conformational change of PCE.

中文翻译：

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磷酸盐系高效减水剂在单组分碱活性渣中的作用机理


导致聚羧酸醚 （PCE） 高效减水剂在双组分碱活化渣 （AAS） 中分散能力受损或丧失的机制已被广泛研究，但对 PCE 在单组分 AAS 系统中如何发挥作用或失去分散效率的科学认识有限，特别是那些使用更绿色的碳酸盐基固体活化剂制备的体系。本研究研究了磷酸盐基 PCE 在由 K2CO3 或 K2CO3 和 CaO 的组合激活的单组分 AAS 中的分散和吸附行为。我们的研究结果表明，在 K2CO3 活化渣系统中，磷酸盐基 PCE 效率的损失主要是由于 PCE 分子的构象收缩，这恶化了碱性活化溶液中的空间排斥力，而不是 PCEs 在碱性溶液中的不溶性或 PCE 与碳酸盐阴离子之间的竞争吸附在溶解的渣粒上。在 K2CO3-CaO 活化渣系统中，当 PCE 用量低于 5 mg/g 时，早期沉淀物（例如 C-A-S-H、盖鲁石、方解石）对 PCE 的消耗是导致其效率损失的主要原因;然而，一旦 PCE 剂量超过该阈值，影响 PCE 效率的主导因素就转移到 PCE 的构象变化上。