不同镁硅摩尔比下水化硅酸镁凝胶的微观结构  

Microstructure of Magnesium Silicate Hydrates in Different Mg/Si Molar Ratios

作　　者：肖建敏 胡亚茹[1] XIAO Jianmin;HU Yaru(College of Materials Science and Engineering,Xi’an University of Architecture and Technology,Xi’an 710055,China)

机构地区：[1]西安建筑科技大学材料科学与工程学院,陕西西安710055

出　　处：《建筑材料学报》2021年第6期1131-1138,共8页Journal of Building Materials

基　　金：陕西省自然科学基金基础研究计划项目(2021JQ⁃500);国家重点研发计划课题(2017YFB0309903⁃03);陕西省教育厅重点科学研究计划(20JS079);陕西省教育厅一般专项科学研究计划(20JK0727)。

摘　　要：利用X射线衍射技术(XRD)和^(29)Si固体核磁共振(^(29)SiSSNMR)技术,对不同镁硅摩尔比下氧化镁/硅灰(MgO/SF)试样的水化产物进行了微观结构和形成机理研究.结果表明:生成的水化硅酸镁凝胶(M⁃S⁃H)聚合度较高,结构复杂,M⁃S⁃H的形成离不开氢氧化镁(MH)的形成和解离,二者在Mg^(2+)的争夺方面存在竞争关系;MgO/SF试样水化反应早期主要生成MH,后期主要生成M⁃S⁃H凝胶,龄期的延长有助于M⁃S⁃H的聚合,长龄期养护有利于Q^(1)向Q^(2)、Q^(2)向Q^(3)的转化;富镁条件促进了M⁃S⁃H的生成,长龄期下Mg^(2+)起拆网作用,支链硅氧四面体含量增多;贫镁条件下试样中剩余大量SF未参与反应,长龄期下Mg^(2+)起补网作用,用于构建层状硅酸盐骨架;M⁃S⁃H凝胶是以层状硅氧四面体为主体、包含端链和支链硅氧四面体的复杂非晶相无序结构.The microstructure and formation mechanism of hydration products of magnesia/silica fume(MgO/SF)pastes in different Mg/Si molar ratios were investigated by X⁃ray diffraction(XRD)and ^(29)Si solid state nuclear magnetic resonance(^(29)Si SSNMR)respectively.The results reveals that the formed magnesium silicate hydrates(M⁃S⁃H)is a complex structure with a high degree of polymerization,and the formation of M⁃S⁃H is related to the formation and decomposition of magnesium hydroxide(MH).It is inevitable that M⁃S⁃H and MH competes for the acquisition of Mg^(2+).MH is mainly formed in the early hydration age of MgO/SF pastes while M⁃S⁃H is mainly formed in the late hydration age.The prolongation of hydration time is conductive to polymerization of M⁃S⁃H,and the long curing age is good for the conversion of Q^(1) to Q^(2) and Q^(2) to Q^(3).The MgO/SF paste with higher Mg/Si molar ratio promotes the formation of M⁃S⁃H,and Mg^(2+)plays the role of dismantling network in long curing age,as the result,the content of chain tetrahedra increases.A large amount of unreacted SF remains in the MgO/SF pastes with lower Mg/Si molar ratio,and Mg^(2+)plays the role of network supplementation in long curing age,which is used to construct layered silicate skeleton of M⁃S⁃H.M⁃S⁃H is a complex amorphous structure with mainly layered tetrahedra and chain tetrahedra and branching chain tetrahedra.

关 键 词：镁硅摩尔比 水化硅酸镁凝胶 微观结构 形成机理 

分 类 号：TQ172.79[化学工程—水泥工业]