Production and application of Mg-based CO₂-sequestrated cement binder for near-zero emission concrete

The production of ordinary Portland cement (OPC), a primary concrete material, accounts for approximately 7 % of global CO₂ emissions. To move forward to a carbon-neutral society, decarbonization of the cement and concrete industry is necessary yet faces hard-to-abate challenges since its CO₂ emissions need to be substantially reduced despite the increasing cement consumption driven by the growing population. Therefore, the development of near-zero emission concrete using alternative low-emissions Mg-based cement has been gaining significant interest in literature. This paper explores a method to produce near-zero emission concrete using a novel CO₂-sequestrated Mg-based cement binder. This novel Mg-based cement binder is a blend of magnesium oxychloride cement (Sorel cement, SC) and magnesium carbonates (MC). Its raw materials can be produced using abundant seawater and CO₂ via a negative emission technology. To investigate the effectiveness of CO₂ mineralization with MgO into MC, two different methods to drive the MgO and CO₂ reaction in a pressured vessel and bead mill were explored. Concrete mixes were optimized using blends of SC and MC (SCMC) with different compositions and particle sizes. Initial setting time over one hour and compressive strength up to 70 MPa were obtained, which are adequate for concrete structure applications. The assessment of CO₂ emissions shows SCMC binder concrete emits about 2 kg-CO₂/m³, illustrating an innovative production technology of near-zero emission concrete.