Abstract

Ways to reduce cement-related carbon emissions are actively sought. One possible solution is partial substitution of Portland cement by alkali-reactive glass. We report on low-CO₂ glass compositions that have high alkali solubility derived from industrial basaltic stone wool compositions. We found that highly alkali-soluble glasses can be formed with glass compositions that in principle can be made using silicate minerals which have no raw material-related CO₂ emissions. The reason behind the reactivity of these glasses is thought to be caused by the dilution of the main network-forming species, silicon, which is further enhanced by phase separation, forming phases with high-silicon and low-silicon concentrations. Phase separation in alumina-rich samples is further studied and occurs at moderate cooling rates. The effect of glass-glass phase separation is discussed in the context of reactive glasses in cementitious systems. The results indicate that controlled phase separation could decouple CO₂ emissions from the reactivity of glassy supplementary cementitious materials.