Effects of steel slag on the properties and microstructure of magnesium oxysulfate cement prepared by magnesium desulfurization byproducts

The magnesium oxysulfate (MOS) cement has problems of short setting time, poor water resistance, and volume instability. This paper investigates the potential of steel slag (SS) to modify the properties and microstructure of the MOS cement prepared by magnesium desulfurization byproducts (MDBs). The results showed that SS delayed the setting time, restrained the volume shrinkage, and improved the water resistance of the MOS cement. The hydration products of the MOS cement were the fibrous 318 phase (3 Mg(OH)2•MgSO4•8H2O), lamellar Mg(OH)2, and MgCO3. The addition of SS increased the pH and decreased the overall hydration reaction rate and the amount of Mg(OH)2 in the MOS cement. SS reacted with Mg(OH)2 at the late stage to form an amorphous M–S–H gel, which increased the gel pore volume and the density of the cement. In conclusion, SS enhanced the application potential of MOS cement, through improving its macroscopic properties.