Carbonated MgO concrete with improved performance: The influence of temperature and hydration agent on hydration, carbonation and strength gain

Carbonation plays a key role in the strength gain of reactive MgO cement (RMC)-based concrete formulations. Low hydration of MgO limits the subsequent carbonation and associated strength gain. This study improves the mechanical performance of carbonated RMC concrete mixes with the introduction of a hydration agent (HA) and high temperature pre-curing (HTPC). The influence of HA and HTPC on hydration, carbonation and microstructural development was investigated through isothermal calorimetry, TGA, XRD, ATR-FTIR and SEM. Implementation of HA and HTPC increased the rate and degree of hydration. The increased brucite content led to higher carbonation degrees, accompanied by lower water absorption and higher density and strength values. Improvement of the morphology of carbonates resulted in 40% higher strengths than the control mix, reaching 56 MPa at 28 days. These mixes provided equivalent strengths to the 28-day strength of the control mix at 7 days, therefore shortening the curing period by 75%.