Stability of carbon dioxide bubbles for the production of lightweight concrete

CO₂ foam concrete has been proposed as a potential carbon sequestration method. Compared with traditional air foaming, CO₂ foaming has the advantages of high foaming efficiency, good system compatibility, and the ability to simultaneously achieve carbon reduction. However, in high-sodium cement environments, CO₂ bubbles are prone to instability due to high solubility, austenite recrystallization, and liquid film drainage, resulting in uneven pore structure and decreased mechanical properties, which restricts its industrial application. A comprehensive investigation integrating experimental characterization and molecular dynamics (MD) simulations was conducted to evaluate the foam stability of three anionic surfactants: sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), and sodium bis (2-ethylhexyl) sulfosuccinate (AOT). Macroscopic analyses revealed that AOT-stabilized foams exhibited the most compact and uniform microstructure with superior long-term stability, attributed to its dual alkyl chains forming a robust viscoelastic interfacial film that suppresses Ostwald ripening and bubble coalescence. SDBS foams showed intermediate performance, while SDS-derived foams displayed the poorest stability due to larger, polydisperse bubbles. MD simulations using the Condensed-phase Optimized Molecular Potentials for Atomistic Simulation Studies (COMPASS) forcefield further elucidated microscopic mechanisms: RDF analysis indicated SDBS had the strongest short-range interactions with CO₂; AOT demonstrated optimal CO₂ retention within 60–120 units distance; and MSD calculations revealed molecular diffusion rates followed the order SDBS > AOT > SDS, dictated by surfactant molecular architectures. These findings clarify the structure-function relationships governing foam stability and CO₂ confinement, providing valuable insights for optimizing CO₂ foam concrete formulations with enhanced performance and carbon sequestration capacity. © 2026 Elsevier Ltd.