Magnesium silicate hydrate (M-S-H) gel is formed by the reaction of brucite with amorphous silica during sulphate attack in concrete and M-S-H is therefore regarded as having limited cementing properties. The aim of this work was to form M-S-H pastes, characterise the hydration reactions and assess the resulting properties. It is shown that M-S-H pastes can be prepared by reacting magnesium oxide (MgO) and silica fume (SF) at low water to solid ratio using sodium hexametaphosphate (NaHMP) as a dispersant. Characterisation of the hydration reactions by x-ray diffraction and thermogravimetric analysis shows that brucite and M-S-H gel are formed and that for samples containing 60wt.% SF and 40wt.% MgO all of the brucites react with SF to form M-S-H gel. These M-S-H cement pastes were found to have compressive strengths in excess of 70MPa

Magnesium silicate hydrate (MSH) gel was formed by reacting magnesium oxide (MgO) with silica fume (SF) in distilled water. The MSH was prepared using a MgO/SF molar ratio of 1.0 (40:60 weight ratio). Samples were analyzed during hydration process up to 300 days at room temperature. The MSH characterization has been carried out using a range of analytical techniques. Quantitative analysis was achieved using thermogravimetric analysis (TG/DTG) with a de-convolution technology. The structure of MSH gel was characterized using solid state nuclear magnetic resonance (²⁹Si NMR) and Fourier transform infrared (FT-IR) spectroscopy. Transmission electron microscopy (TEM) was used to investigate MSH microstructure. Compared with natural magnesium silicate hydrate minerals, the structure of MSH gel is highly disordered and generates on the surface of particles, producing a shell structure with cavity. The molecular structure of MSH phase is layered. The results also show that the extent of polymerization of MSH gel is related to the solution pH during hydration.

Municipal solid waste incineration (MSWI) fly ash must be treated properly prior to being disposed in the security landfill due to its serious pollution toxicity. Nowadays, lots of studies have demonstrated that cement‐based stabilization/solidification could reduce the toxicity pollution effectively by encapsulating the heavy metals into cement matrix, which leads to greater capacity and weight. This paper compares and discusses the MSWI fly ash treatment with the mostly used matrix materials such as Portland cement, phosphate cement, aluminate cement, and alkaline activated cement. Moreover, immobilization mechanism introduced by the interaction between the MSWI fly ash and hydrated cement matrix materials, such as the physical cementing effect, adsorption, isomorphous replacement, and complex precipitation, was explored in depth. The paper also pointed out some reasonable development directions for cement‐based stabilization/solidification technology to improve the effectiveness and application of cement‐based stabilization/solidification technology.