The effect of concentration changes of magnesium chloride on the mechanical and hydration properties of magnesium oxychloride (Sorel) cement was investigated. The results demonstrated that a concentration change of MgCl2 can strongly affect the properties of the Sorel cement. The amount of magnesium chloride was varied from 0.5 to 1.9 moles and the cold crushing strength (CCS) of each sample was measured after 2, 4, 10, and 20 days. The bulk density and porosity were also measured. X-Ray diffraction (XRD) of the matrix phases was investigated. The morphology and microstructure of the phases were characterized using a scanning electron microscope (SEM). The micrographs showed a vast formation of needle shaped crystallites of 5MgO •MgCl2 •8H2O (phase 5). The behavior arising from evaporation of water from the surface of the cement and the nature of hydration products were investigated. It was shown that a molar ratio of MgO/H2O = 13 : 12 with 1.5 moles of MgCl2 •6H2O can produce a promising matrix composition for a proper design.

Keywords: Magnesium oxychloride cement, Sorel, Magnesia, Magnesium chloride, Hydration process, Needle shaped crystal.