长龄期下水化硅酸镁凝胶微观结构  

Microstructure of Magnesium Silicate Hydrates in Long Curing Age

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,西安710055

出　　处：《硅酸盐学报》2022年第8期2221-2229,共9页Journal of The Chinese Ceramic Society

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射线衍射分析、Fourier变换红外光谱、固体核磁共振和热重分析技术对长龄期下不同Mg/Si摩尔比的水化硅酸镁试样进行微观结构研究,旨在为深入表征水化硅酸镁凝胶(M–S–H)提供一定技术支撑和理论基础。结果表明:M–S–H主体为层状硅氧四面体结构,包含部分端链和支链硅氧四面体,富镁条件下M–S–H层状结构以Q_(a)^(3)为主,贫镁条件下以Q_(b)^(3)为主。随着Mg/Si摩尔比增大,MgO–SiO_(2)–H_(2)O体系中M–S–H凝胶Q^(1)、Q^(2)、Q^(3)含量均增多,其中Q^(2)增幅最大,Mg(OH)_(2)(MH)含量增大,未反应的Q_(silica)^(4)含量迅速降低,水化反应程度提高,凝胶有序度下降,凝胶聚合度降低。长龄期条件MH解离速度增大,凝胶结构复杂度增大;延长龄期有利于层状硅氧四面体结构多样化的形成,有助于M–S–H聚合反应的发生。M–S–H凝胶中水分子以自由水、结合水和结构水形式存在,结构水中,羟基与Mg^(2+)键合或与吸附水结合,端链硅氧四面体和支链硅氧四面体与羟基直接相连,层状硅氧四面体未直接与羟基键合,凝胶中Mg与Si以及结构水与Si的摩尔比为固定值。The microstructure of magnesium silicate hydrates pastes in different Mg/Si molar ratios was investigated by X-ray diffraction,Fourier transform infrared spectroscopy,solid-state nuclear magnetic resonance and thermogravimetric analysis,respectively.The results reveal that the formed magnesium silicate hydrates(M–S–H)is a main structure of layered tetrahedra with some chain tetrahedra and branching chain tetrahedra.The layered tetrahedra is dominated by Q_(a)^(3) at a higher Mg/Si molar ratio,and the layered tetrahedra is Q_(b)^(3) at a lower Mg/Si molar ratio.The contents of Q^(1)、Q^(2) and Q^(3),especially Q^(2) in the system of Mg O–Si O_(2)–H_(2)O,all increase as the Mg/Si molar ratio increases.Also,the content of magnesium hydroxide(MH)increases,the content of unreacted Q^(4) silica decreases rapidly,the degree of hydration reaction increases,the degree of gel order and the degree of gel polymerization decrease.At a long age,the decomposition rate of MH increases,and the complexity of the gel structure increases,and the prolonged hydration time is conducive to the formation of diversified layered silicon-oxygen tetrahedral structures and the occurrence of M–S–H polymerization.The water structures of M–S–H are free,confined and structural water.The hydroxyl group is bonded with Mg^(2+)ions or combined with adsorbed water.Chain tetrahedra and branching chain tetrahedra are linked to hydroxyl groups,but Q^(3) silicate sites are not directly linked to hydroxyl groups.The molar ratio of Mg and Si or structural water and Si in a gel is a fixed value.

关 键 词：水化硅酸镁 长龄期 微观结构 凝胶水分子 

分 类 号：TQ172.79[化学工程—水泥工业]