Sustainable MgO-calcined clay cementitious material: Reaction mechanism, strength development and performance enhancement via initial CO2 stirring

With the massive utilization of concrete and other cement-based materials worldwide, the high carbon emissions and energy consumption have become severe issues. This study proposes a sustainable cementitious material based on MgO and calcined clay and investigates its reaction mechanism and strength development by combining experimental characterizations and thermodynamic modelling. Furthermore, the performance of the MgO-calcined clay cementitious material is enhanced by CO2 stirring. The results indicated that the introduction of CO2 during stirring generates massive high reactive magnesium carbonate nano/micro-particles. It provides the nucleation sites for promoting the formation of hydration products and reacts with calcined clay to form carbonate-type hydrotalcite. Due to the unique advantages of CO2 stirring in the MgO-calcined clay system, the performance of sustainable cementitious material is remarkably enhanced, providing a new routine for developing high-performance low-carbon building materials.