Characterization of cost-effective green engineered magnesium oxysulfide cement-based composites (MOSC-ECC) prepared by replacing MgO in magnesium oxysulfate cement with slag

A cost-effective green engineered magnesium oxysulfide cement-based composites (MOSC-ECC) which was prepared with magnesium oxysulfate cement (MOSC) and large-volume solid waste (slag) in this paper. The macro and micro mechanical properties, thermal conductivity, water resistance, evolution of hydration products and microstructure of MOSC-ECC were studied. The energy consumption, carbon emissions, and cost of MOSC-ECC were calculated and compared with traditional ECC. Test results showed that adding slag instead of light-burned MgO can increase the strain-hardening strength and energy indices of MOSC-ECC, and improve the ductility. In addition, the incorporation of slag lowered the proportion of 5Mg(OH)₂·MgSO₄·7 H₂O phase (517 phase), led to a decrease in the strength, density and thermal conductivity of the MOSC-ECC. Compared with traditional OPC-based ECCs, the prepared MOSC-ECC showed a reduction in embodied energy by approximately 32 %, a reduction in CO₂ emission of around 60 %, and a reduction in material costs more than 38 %. Therefore, slag can be used as the main component of MOSC-ECC, and the dosage can be up to 50 % by weight of MgO, which has obvious economic and environmental benefits.