Seawater-based geopolymers potentially capitalize on the abundant seawater and reduce the CO₂ emissions for marine/offshore constructions. Unlike the well-documented seawater ions (e.g., Ca²⁺, Na⁺, and Cl⁻), existing studies on magnesium-ion (Mg²⁺)-induced changes of geopolymers, especially the non‑calcium mixtures, have been limited. In this study, Mg²⁺ was confirmed to retard the setting of sodium-silicate activated metakaolin from Vicat and calorimetry tests. Through chemical extraction and spectroscopy characterization, the retardation mechanism was found mainly due to the consumption of OH⁻ via Mg²⁺ in the activating solution, which decelerated the dissolution and condensation during geopolymerization. Supplemental Vicat penetration under a controlled alkalinity indicated a further retardation via the “coating effect” of magnesium silicate hydrate (M-S-H) gels, which were produced by the interaction of Mg²⁺ and the aqueous silicates. These findings substantiate the tailorability of setting by Mg²⁺, an abundant marine resource, thereby paving the way to develop eco-friendly cementitious binders with balanced performance.

海水基地质聚合物有可能利用丰富的海水并减少海洋/近海建筑的CO _2排放。与有据可查的海水离子（例如Ca ²⁺、Na ⁺和Cl ^-）不同，现有的关于镁离子（Mg ²⁺）引起的地质聚合物变化（尤其是非钙混合物）的研究是有限的。在本研究中，维卡和量热测试证实 Mg ²⁺可以延迟硅酸钠活化偏高岭土的凝固。通过化学萃取和光谱表征，发现延迟机制主要是由于活化溶液中的Mg ^{2+消耗了OH - ，从而减缓了地质聚合过程中的溶解和缩合。}在受控碱度下补充维卡渗透表明通过水合硅酸镁 (MSH) 凝胶的“涂层效应”进一步延迟，该凝胶是由 Mg ²⁺和水性硅酸盐相互作用产生的。^{这些发现证实了Mg 2+} （一种丰富的海洋资源）凝固的可定制性，从而为开发具有平衡性能的环保型胶结材铺平了道路。