Effect of small quantities of magnesium chloride on low-temperature calcination of hydromagnesite and its application in the preparation of magnesium oxychloride cement

Currently, MgO is primarily obtained through the calcination of magnesite. To ensure complete decomposition of the ore, the preparation temperature for LBMP (light-burned magnesium oxide powder) is typically maintained above 800 °C, with processing times exceeding 2 hours. This study proposes an energy-saving calcination strategy that reduces the decomposition temperature of hydromagnesite (4MgCO3·Mg(OH)2·4H2O) by incorporating trace amounts of MgCl2. Furthermore, multiple technical approaches were employed to investigate the mechanism of this calcination strategy and its feasibility for producing magnesium oxychlorite cement. Results demonstrate that this method enables complete decomposition of MgCO3 in magnesite at 700 °C within 2 hours of calcination, yielding MgO exhibiting excellent dispersion and reactivity. This process effectively prevents the formation of large amounts of Mg(OH)2 induced by amorphous MgCO3 during the hydration of active MgO. Consequently, more active MgO transforms into coarse, needle-like Phase 5, filling the pores and matrix of MOC, significantly enhancing the mechanical properties of the prepared MOC. This demonstrates the method's great potential in preparing LBMP and its application in producing MOC cementitious materials.