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 CO2 release. This study used brucite and dilute sulfuric acid to prepare magnesium sulfate (MgSO4) 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 MgSO4 solution temperatures on sustainable low carbon MOSC were investigated. The results showed that as the temperature of the MgSO4 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 MgSO4 solution exhibited increasing compressive strength, reaching 34 MPa at 3 d age. However, the samples prepared with 40 °C and 60 °C MgSO4 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 MgSO4 solution temperatures. Under 60 °C of the MgSO4 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%.