Advances in the hydration of reactive MgO cement blends incorporating different magnesium carbonates

Hydration of reactive magnesia cement (RMC) is limited by the formation of a Mg(OH)2 surface-layer on unreacted MgO particles. This study improved RMC hydration by using magnesium acetate (MA), along with hydromagnesite (H) and magnesite (M) as RMC replacements. While MA accelerated hydration and resulted in the formation of needle-like artinite, inclusion of M led to rosette-like crystals. The accumulated nucleation and growth of low-crystallinity Mg(OH)₂ on H particles in a bird nest-like arrangement was observed for the first time in literature. This low-crystallinity Mg(OH)₂ could be prone to carbonation. The replacement of up to 40% RMC with M in the presence of MA improved the compressive strength of RMC samples by 240%. This performance enhancement was supported by microstructure densification via the compact formation of hydrate and carbonate phases, defining M as a feasible partial RMC substitute.