Effects of calcination process of salt lake magnesium slag on the properties of magnesium oxysulfide cement

To promote large-scale utilisation of magnesium resources from salt lakes, low-cost magnesium oxysulfate (MOS) cement was prepared using a magnesia-rich residue as the raw material to produce light-burned magnesia after washing and calcining the raw material. The effects of calcination temperature (CT) on the properties of calcined products and the phase and microstructure of the MOS cement prepared from the calcined products were studied. The results showed that magnesium hydroxide was completely decomposed after calcining at 500°C for 2 h. When the CT reached 500°C and continued to increase, the activity and the crystal size of the magnesium oxide both increased. Microstructural analysis showed that a high CT was beneficial to the growth of the needle-shaped phase 5 (5Mg(OH)₂.MgSO₄.7H₂O) of the prepared MOS. A high CT also resulted in high porosity.