Effect of alumina on the carbonation reactivity of calcium aluminosilicate glasses

Abstract

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 CO₂ mineralization, this study highlights the role of Al₂O₃ in the carbonation of synthetic CaO·Al₂O₃·SiO₂ glasses. The incorporation of Al₂O₃ impedes the carbonation reaction by modifying the glass structure at multiple length scales. At the atomic scale, the formation of [AlO₄]⁻ removes the non-bridging oxygens which serve as sites for Ca²⁺/H⁺ exchange, and disrupts the Ca²⁺ channels by clustering with [SiO₄] in the Q⁴ 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 Ca²⁺. This effect hinders the heterogeneous nucleation and thus the morphology of CaCO₃ precipitated on glass particles.