Ethylenediamine tetra-acetic acid (EDTA) and its disodium salt derivative (EDTA-Na) (0.5% weight of MgO powder) were incorporated into MgO–MgSO₄–H₂O ternary system to prepare magnesium oxysulfate (MOS) cement. The single effect of EDTA/EDTA-Na as well as the synergistic effect of EDTA/EDTA-Na and citric acid (CA) on the hydration mechanism, phase composition, microstructure and mechanical properties of MOS cement were investigated. The results showed that EDTA and EDTA-Na addition induced no new phase, but the magnesium-EDTA complexes formed by EDTA⁴⁻ and Mg²⁺ ions acted as nuclei for the hydration products, including brucite, 3Mg(OH)₂·MgSO₄·8H₂O (318 phase) and 5Mg(OH)₂·MgSO₄·7H₂O (517 phase). This helped to form a more homogeneous and compact microstructure, thereby improving the durability and volume stability of MOS cement in air curing condition. Moreover, the synergistic effect of EDTA/EDTA-Na and CA preferred the formation of 517 phase to that of brucite. It further improved the water resistance of MOS cement. In this study, EDTA and EDTA-Na were found to be effective additives in improving the characteristics of MOS cement.

将乙二胺四乙酸（EDTA）及其二钠盐衍生物（EDTA-Na）（0.5%重量的MgO粉末）掺入MgO-MgSO ₄ -H ₂ O三元体系中制备硫酸氧镁（MOS）水泥。研究了EDTA/EDTA-Na的单一作用以及EDTA/EDTA-Na与柠檬酸(CA)的协同作用对MOS水泥的水化机理、相组成、微观结构和力学性能的影响。结果表明，EDTA和EDTA-Na的加入没有产生新相，但EDTA ^4-和Mg ²⁺离子形成的镁-EDTA配合物作为水镁石、3Mg(OH) ₂ ·MgSO _{4 等}水合产物的晶核。·8H ₂O（318相）和5Mg(OH) ₂ ·MgSO ₄ ·7H ₂ O（517相）。这有助于形成更均匀和致密的微观结构，从而提高 MOS 水泥在空气固化条件下的耐久性和体积稳定性。此外，EDTA/EDTA-Na和CA的协同作用比水镁石更倾向于形成517相。进一步提高了MOS水泥的耐水性。本研究发现 EDTA 和 EDTA-Na 是改善 MOS 水泥特性的有效添加剂。