Wet carbonation and stabilities of Fe(II)-containing materials

Fe(II)-rich clays and industrial by-products are emerging clinker substitutes that can decarbonise cement production by participating in hydration, alkali-activation, or carbonation reactions in cementitious materials. However, the formation and stability of Fe(II) carbonates during storage and the service life of cementitious composites remain unclear. This study investigated formation kinetics, phase assemblage, and air-stability of Fe(II) carbonates, which were synthesized by wet carbonation under ambient conditions. The results revealed amorphous (hydrous) iron carbonates formed rapidly within 5 minutes, followed by gradual formation of siderite within 30 minutes, reaching a carbonation degree of 78%. Upon air exposure, siderite began decomposing after 6 hours, whilst the amorphous carbonate phases lost CO 2 slower over 36 hours. All Fe(II) carbonates fully lost CO 2 within 6 days, indicating their limited air stability. This study paves the way for engineering CO 2 capture and storage in Fe(II)-rich cementitious composites.