Hydration, carbonation, strength development and corrosion resistance of reactive MgO cement-based composites

Abstract

Reactive-MgO cement (RMC) is an emerging material with the potential to become a long-term sustainable alternative to ordinary Portland cement (OPC) due to its capability to sequester CO2 for strength development. This study focused on the hydration, carbonation, mechanical, and durability properties of RMC-based composites. The results showed that an environment of 20% CO2 induced rapid carbonation and formation of hydrated magnesium carbonates in the composites, leading to pore refinement and and strength gain to a level similar to that of OPC-based counterpart. The carbonation rate slowed under an extended carbonation period, and an ultimate effective CO2 sequestration factor of 4.6% was achieved at 28 days. The low pH environment within the RMC matrix induced a poor or no passivity of the embedded rebars, and an active corrosion was observed from the start of the electrochemical measurement. Though, the matrix densification as a result of the carbonation helped to considerably reduce the corrosion activity of the rebars.