Stability of MgO-modified geopolymeric gel structure exposed to a CO₂-rich environment

The present study investigated the microstructural and compositional formations of the gel phase in MgO-incorporated geopolymer exposed to a high CO₂ concentration. Samples were synthesized by the alkali-activation of fly ash with different dosages of MgO. The results showed that a higher level of MgO incorporation into a geopolymer exposed to a CO₂-rich environment decreases the porosity, corresponding to an increase in the compressive strength. Furthermore, the microstructural densification of geopolymer caused by the formation of Mg-bearing hydrate was observed, and this may have important implications for use in high-CO₂ conditions by reducing the diffusivity of CO₂ through the pore structure.