Comparative study on characteristics and microstructure of magnesium silicate hydrate utilizing quartz and silica fume as siliceous raw materials
Kunyi Zheng, Xiaoli Xie, Guangjun Gou, Xuemei Chen, Yulin Huang, Jian Gao
Abstract
Hydrated magnesium silicate (M-S-H) samples were prepared utilizing reactive magnesia and quartz with six various Mg/Si molar ratios by the autoclaved curing system. The characteristics and microstructure of M-S-H samples were examined using XRD, TGA, FTIR, SEM and 29Si MAS NMR. Additionally, silica fume was utilized as the siliceous raw material to prepare the M-S-H samples that served as controls. The results showed quartz can be utilized as siliceous raw material for preparing M-S-H. Compared with the samples employing silica fume, the M-S-H samples utilizing quartz as the siliceous material had a layered structure and a significant amount of silicate polymerization. Moreover, the SEM images of M-S-H utilizing quartz as the raw material exhibited a denser structure when compared to the microstructure of granular morphology of M-S-H with silica fume. Remarkably, the existence of quartz as a siliceous raw material led to the production of M-S-H with an antigorite structure. At the same time, the 29Si MAS NMR observations revealed that quartz as a siliceous raw material is favorable for the conversion of Q2 to Q3, resulting in improvement of polymerization degree of M-S-H silicone tetrahedron. The study demonstrated that it is the feasible to prepare M-S-H by replacing silica fume with quartz, which can provide a reference and choice for the preparation of green cementitious materials.