硅粉偏高岭土基地聚合物微观结构分析

Microstructure of Silica Fume-Metakaolin Based Geopolymer

采用硅粉、偏高岭土和碱激发剂制得硅粉-偏高岭土基地聚合物.应用X射线衍射、扫描电镜-能谱、红外光谱和核磁共振等技术分析硅粉-偏高岭土基地聚合物的化学组成与微观结构,揭示硅粉-偏高岭土基地聚合物具有独特耐久性的原因.结果表明:硅粉-偏高岭土基地聚合物为无定形的碱金属铝硅酸盐胶体,Si/Al摩尔比较高,与硅酸盐水泥水化产物完全不同.加入碱激发剂发生化学反应后,偏高岭土和硅粉中对应于Si—O—Si键非对称伸缩振动的谱带吸收强度减弱,同时向低频率方向移动,铝氧四面体取代Si—O—Si链上部分硅氧四面体.硅粉-偏高岭土基地聚合物中的铝氧四面体和硅氧四面体相互键接构成空间三维网络状结构,从而使其具有优良的耐久性.

To explain the cause of excellent durability, X-ray diffracti0n（XRD）, Fourier transform infrared spectrum（FTIR）, scanning electron microscope and energy dispersive（SEM-EDS） and nuclear magnetic resonance（NMR） were used to investigate the chemical composition and mierostructure of silica fume- metakaolin based geopolymer which was prepared with silica fume, metakaolin and alkali activator. The results show that the geopolymer has an amorphous structure without any special peak corresponding to crystal in XRD spectrogram. This amorphous product is alkali alumino-silicate with a higher Si/A1 mole ratio that differs from hydrated products of cement. After alkali activator is used, the peaks corresponding to Si--O--Si asymmetric stretching mode in FTIR spectrogram of metakaolin and silica fume have a shift to low frequency. It means that [AlO4] tetrahedrons replace some [SiO4] tetrahedrons in the Si--O--Si chain. Al is in the state of tetra-coordinate in silica fume-metakaolin based geopolymer. A three-dimensional framework structure which consists of [SiO4 ] tetrahedron and [AlO4 ] tetrahedron comes into being with the result that silica fume-metakaolin based geopolymer shows excellent durability.