The hydration mechanism of magnesium oxysulfate cement prepared by magnesium desulfurization byproducts

The byproducts of flue gas desulfurization using magnesium (Mg) oxides in aqueous environment are hard to utilize. In order to study the potential of using Mg desulfurization byproducts for the preparation of Mg oxysulfate cement, this paper investigates the hydration mechanism of Mg oxysulfate cement (DMOS) prepared by Mg desulfurization byproducts. Mg oxysulfate cement (MOS) prepared using pure heptahydrate sulfuric acid is used as control. The material characterizations were conducted by X-ray diffraction, fourier transform infrared spectroscopy, mercury intrusion porosimetry, hydration heat release analysis, pH and scanning electron microscopy-energy dispersive spectroscopy. The results shows that the 28 days compressive strength of DMOS reached 28.86 MPa, which was 81% of that of MOS with the same preparation condition. The hydration products of DMOS are mainly 3 Mg(OH)2⋅MgSO4⋅8H2O (318 phase), MgCO3 and Mg(OH)2. The 318 phase exists in the form of needles, and there are a large number of flake Mg(OH)2 crystals and incomplete MgO. The hydration exothermic trend of DMOS is similar to MOS, but delayed a little bit. The maximum heat release of DMOS is higher than that of MOS. The obtained results would provide a reference for the application of Mg desulfurization byproducts in cement preparation industry.