Properties and microstructure of basic magnesium sulfate cement: Influence of silica fume.

• Industrial waste silica fume (SF) is used to improve the performance of basic magnesium sulfate cement (BMSC). • Incorporation of SF can enhance the mechanical properties of BMSC significantly. • Hydration behavior and process of BMSC influenced by SF are studied. • Microstructure and phase evolution of BMSC are characterized and analyzed. Silica fume (SF) as an important supplementary cementitious material has been widely used in Portland cement, but few published articles have reported on the effect of SF on the performance and hydration mechanism of basic magnesium sulfate cement (BMSC). In the present work, the properties, microstructure and hydration mechanism of BMSC influenced by SF was studied systematically. The results show that the setting time and compressive strength of BMSC may increase with the increase of SF content, while the hydration heat will decrease with the increase of SF content. Mercury intrusion porosimetry (MIP), X-ray computed tomography (X-CT), scanning electron microscope- Energy dispersive spectrometer (SEM-EDS) results show that SF exhibits filling effect in the BMSC matrix, which makes the microstructure of BMSC matrix with SF more compact. In addition, solid-state magnetic resonance (NMR) and SEM-EDS analysis indicate that the activity of SF was excited in the BMSC matrix, resulting in the formation of M−S−H gel. [ABSTRACT FROM AUTHOR]