Carbonation of natural fibers reinforced MgO-SiO₂ (NFs-MS) composites

Abstract

The heavy reliance of reactive magnesia cement (RMC) on CO2 sources to gain sufficient mechanical strength limits its productivity. The present work developed natural fibers reinforced MgO-SiO2 (NFs-MS) composites, in which the formation of magnesium-silicate-hydrate (M-S-H) yielded sufficient early strength (e.g., >30 MPa), and subsequent carbonation of residual brucite enabled continuous strength development (e.g., >70 MPa). The presence of NFs 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. Moreover, carbonation curing densified the fiber-matrix interface zone, leading to improved fiber-matrix interfacial properties and tensile performance. The results from aqueous carbonation test show that the synthetic M-S-H has greater chemical stability compared to MgO/brucite. However, partial leaching of Mg2+ from M-S-H was also observed, implying the carbonation potential of M-S-H phase. These findings suggest that NFs-MS composites hold great potential to be directly applied in load-bearing structures without requirement for special CO2 pre-curing