Carbonation of Hollow Natural Fibers Reinforced MgO-SiO2 (HNFs-MS) Composites

Reactive magnesium cement (RMC) heavily relies on the elevated CO2 curing to gain strength, which limits its productivity and increases the curing cost. To address this problem, a hollow natural fibers reinforced MgO-SiO2 (HNFs-MS) composite was proposed in this study, in which the formation of magnesium-silicate-hydrate (M-S-H) provided sufficient early strength, and subsequent carbonation of residual MgO/Mg(OH)2 enabled continuous strength development and CO2 sequestration. The results showed that the strength development under moisture curing depends on the formation of M-S-H, while the carbonation of residual MgO/Mg(OH)2 dominates under carbonation curing. The incorporation of HNFs in MS composites not only accelerates the strength gain under moisture curing and subsequent carbonation curing, but also effectively improves the volume stability and CO2 sequestration, especially in deep regions. This is relevant to the porous microstructure of HNF, which can be the pathway for free CO2 diffusion inwardly and offset the surrounding matrix expansion.