磷酸镁胶凝材料的水化机理研究

Mechanism of Hydration Reaction in Magnesia-Phosphate Cements

以死烧MgO(M)、KH2PO4(P)和硼砂(B)按一定比例制备磷酸镁水泥(MPC),采用精密pH计测试MPC体系(水灰比为5)28d的pH变化,多路温度测试仪记录MPC体系6h内的放热特性,以探讨MPC胶凝体系的水化动力学特征。采用XRD、差热分析(DTA)分析各龄期水化样中的反应产物,扫描电镜观察微观形貌,结果表明磷酸镁水泥的主要水化产物为MgKPO4·6H2O(MKP),MKP晶体的成核与生长需满足一定水化动力学基础,在水化初期发现有少量K2Mg(HPO4)2·4H2O作为MKP中间相而产生;水化1d后的试样中可发现部分棒状和板状的MKP结晶,经过28d后基体发展为结构密实、充分水化的整体;在此基础上进一步探讨了MPC材料的水化硬化机理。

Magnesia-phosphate cement was prepared by mixing of dead-burned magnesia （M）, monopotassium phosphate （P）, and borax （B） with a certain proportion Accurate pH-meter was used to determine variety of pH in MPC system （with water/cement ratio=5） within 28 days, and multi-channel temperature monitor recorder was applied to record the exothermic character of MPC system within 6 hours, besides, hydration kinetics behaviors were explored. Hydration products of MPC specimens were characterized by XRD and DTA, and morphology analysis was conducted by SEM. The results show that, MgKPO4·6H2O（MKP） is the main hydration product, and the formation and nucleation of MKP must cater for the sufficient hydration dynamics condition, therefore, a small quantity of K2 Mg（HPO4 ）2·4H2O was found in 3 h specimens as the intermediate phase. Rod-like and tabular MKP crystalline appears in 1 d specimen, and a dense microstructure with deep hydration degree progressively forms, and on the basis of which, mechanism of hydration reaction in MPC material are discussed thereafter.