Sol–gel-stabilized CO2 foam for enhanced in-situ carbonation in foamed fly ash backfill materials

A novel highly stable aqueous foam was synthesized using CO₂, sodium silicate (SS) and anionic surfactant of sodium dodecylbenzene sulfonate. The influence of CO₂ foam on the mechanical properties and its underlying mechanisms of foamed backfill material was investigated. The experimental results revealed that the addition of CO₂ and SS effectively reduced the drainage of the foam while strengthening the liquid film of the Plateau borders, which stabilizes the foam. The excellent stability is attributable to the gel network developed after SS exposed to CO₂, that adhere to the foam surface. Furthermore, due to the interaction between encapsulated CO₂ and hydration products, micro CaCO₃ formed and filled the pore wall; thus, precast foam forms robust pore structures in the hardened foamed backfill.