Tuning the phase structure and mechanical performance of magnesium oxychloride cements by curing temperature and H2O/MgCl2 ratio

The curing temperature and H2O/MgCl2 mole ratio are the two main factors that affect the structure and mechanical performance of the magnesium oxychloride (MOC) cement. In this work, different curing temperatures and H2O/MgCl2 mole ratios were used to synthesize MOC cement. The structure of the MOC cement samples was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The mechanical performance of the samples was also evaluated. The results indicated that the effect of curing temperature on the phase structure and mechanical performance of the MOC cement was closely involved with the H2O/MgCl2 mole ratio in the MgO-MgCl2-H2O ternary system. As for the mechanical properties, the compression strength was closely related to the phase structure and microstructure. When cured at 25 °C, the MOC with the H2O/MgCl2 mole ratio of 11 possessed a more dense microstructure, and higher compression strength (36.95 MPa) as compared with the MOC with the H2O/MgCl2 mole ratio of 20 (16.19 MPa). When cured at 40 °C, the MOC with the H2O/MgCl2 mole ratio of 13 exhibited more phase 5 structure, and higher compression strength (50.84 MPa) as compared with the MOC with the H2O/MgCl2 mole ratio of 20 (4.35 MPa).