Improving the performance of reactive MgO cement-based concrete mixes

•Quantity and morphology of carbonates determine the performance of MgO cement mixes.•Low hydration and high water demand of MgO limits strength gain in concrete mixes.•Inclusion of hydration agent enhanced MgO hydration, carbonation and strength gain.•Dispersant agent use reduced water demand, improved morphology and performance.•28 day strength of MgO concrete mixes containing these agents increased by over 50%.

Low hydration and high water demand of MgO limits strength gain in MgO cement-based formulations. This study enhanced the microstructure and performance of MgO concrete mixes by increasing hydration and lowering water demand via the introduction of hydration (HA) and dispersion (DA) agents. Hydration and carbonation mechanisms were evaluated by isothermal calorimetry, TGA, XRD, FTIR and SEM. HA increased MgO dissolution and brucite precipitation. DA reduced water content and resulted in denser microstructures by increasing CO2 diffusion. Formation of dense carbonate networks with improved morphologies resulted in 28-day strengths of 45 MPa, which were >50% higher than the control sample.