Synergetic regulation of hydration and carbonation of reactive MgO cement by amino acids

This study investigates the role of L-aspartic (L-Asp) in regulating the crystallisation of hydrated magnesium carbonates (HMCs) in carbonation-cured reactive MgO (RM). The effects of L-Asp on hydration kinetics, bulk density, compressive strength, phase composition, carbon sequestration, microstructure and morphology of RM composites were examined to understand its influence on the coupled hydration and carbonation processes. It has been found that L-Asp delays the precipitation of Mg²⁺ and OH⁻, promoting the formation and stabilisation of the metastable nesquehonite (MgCO₃·3H₂O) polymorph. Carbonated composites incorporating L-Asp demonstrate a higher carbonation degree and enhanced stability compared to those without L-Asp. Notably, samples containing 0.2 M L-Asp sequestrated 46.7 % more CO₂ than those without amino acids. Additionally, amino acids lead to denser carbonation products with modified morphology, significantly enhancing carbonation efficiency and compressive strength. This study unveils the synergetic mechanism by which L-Asp influences hydration and carbonation in MgO-based binders, contributing to their enhanced performance.