Experimental Study on Preparation of Sustainable Low Carbon Magnesium Oxysulfate Cement (MOSC) Based on Brucite and Dilute Sulfuric Acid

Traditional magnesium oxysulfate cement (MOSC) is prepared from light-burned magnesia, magnesium sulfate heptahydrate with a large amount of energy consumption and CO 2 release. This study used brucite and dilute sulfuric acid to prepare magnesium sulfate (MgSO 4 ) solution where the temperature exceeded 70 °C; light-burned magnesia was added to create a new type of sustainable low carbon MOSC, of which the performances were evaluated. Additionally, the effects of MgSO 4 solution temperatures on sustainable low carbon MOSC were investigated. The results showed that as the temperature of the MgSO 4 solution increased, the setting time and the fluidity of the sustainable low carbon MOSC decreased. The compressive strength of this material showed that the samples prepared with 20 °C MgSO 4 solution exhibited increasing compressive strength, reaching 34 MPa at 3 d age. However, the samples prepared with 40 °C and 60 °C MgSO 4 solution showed compressive strength reduction as 23 and 18.2 MPa at 3 d age. Microscopic analysis revealed that the type of hydration products was not altered by the MgSO 4 solution temperatures. Under 60 °C of the MgSO 4 solution, the content of 3·1·8 crystalline phase in the material increased to 18.5%, while the 5·1·7 crystalline phase decreased to 13.1%. The porosity of the material increased to 26.55%.