Carbon dioxide sequestration in magnesium-based binders

Reactive magnesia cement (RMC) has emerged as a sustainable and technically promising novel binder because of its lower production temperatures than Portland cement and ability to gain strength by sequestering significant quantities of CO₂. Other benefits of RMC include its improved durability under aggressive environments where reinforcement is not present, because of the higher resistance of its hydrate and carbonate phases. The low sensitivity of RMC to impurities enables the utilization of large quantities of wastes and industrial by-products. From an environmental standpoint, the ability of RMC to gain strength via the carbonation process and be fully recycled in concrete mixes, in which it is used as the sole binder, indicates potential for impact on a large scale. This chapter focuses on the reaction mechanisms and associated strength and microstructural development of RMC systems. It reviews the production, characterization, properties, and applications of the main binder phase, MgO, that control the performance of RMC samples. The influence of key factors, such as binder properties, mix design, curing conditions, and presence of additives on the hydration and carbonation reactions, is discussed. Current state of the art and gaps in existing literature are highlighted, supported by recommendations to turn limitations into potential advantages.