Comparative study on characteristics and microstructure of magnesium silicate hydrate utilizing quartz and silica fume as siliceous raw materials

Magnesium silicate hydrate (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 MS-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.