Effect of alumina on the carbonation reactivity of calcium aluminosilicate glasses

Reactivity of silicate glasses, the main component of industrial byproducts such as blast furnace slag and yellow phosphorus slag, is highly linked with their chemical and nano-structural properties. To provide insights on the viability of such materials for use in CO 2 mineralization, this study highlights the role of Al 2 O 3 in the carbonation of synthetic CaO·Al 2 O 3 ·SiO 2 glasses. The incorporation of Al 2 O 3 impedes the carbonation reaction by modifying the glass structure at multiple length scales. At the atomic scale, the formation of [AlO 4 ] − removes the non-bridging oxygens which serve as sites for Ca 2+ /H + exchange, and disrupts the Ca 2+ channels by clustering with [SiO 4 ] in the Q 4 state. At the nanoscale, phase-separated regions were observed particularly in high-Al glasses. During carbonation (when pH = 6), the Al species re-adsorbed on the surface of glass particles preferentially to Ca 2+ . This effect hinders the heterogeneous nucleation and thus the morphology of CaCO 3 precipitated on glass particles.