Effect of air entrainment on the performance of reactive MgO and PC mixes

•Use of air-entraining agent (AEA) in reactive MgO cement (RMC) mixes was studied.•RMC and PC mixes with a range of compositions were compared for their performance.•Strength of RMC mixes depended on the carbonation degree and carbonate morphologies.•AEA improved workability and facilitated CO2 uptake and strength gain in RMC mixes.•Besides hydromagnesite, use of AEA increased formation of nesquehonite in RMC mixes.

This study investigated the influence of air-entraining agents (AEA) on the performance and microstructure of reactive MgO cement (RMC) samples in comparison with Portland cement (PC) samples under different water contents and curing conditions. Porosity, density, workability, strength, pH and thermal conductivity measurements were supported with XRD, TGA/DSC and SEM analyses. Performance of RMC samples depended on the dense formation of carbonate phases such as nesquehonite and hydromagnesite, whereas PC samples gained strength by hydration. Introduction of AEA reduced early strength due to increased air contents. This was compensated by increased CO2 penetration, carbonation and strength gain in longer periods.