Insights into the Carbonation of Industrial Slags: The Effect of Al/Si Ratio on the Carbonation of Calcium Aluminosilicate Glass Constituents and Their Role as Supplementary Cementitious Materials

Calcium aluminosilicate glasses are reactive components in industrial slags. To use them for CO 2 sequestration, understanding how the glasses’ chemistry influences their carbonation reaction behavior is essential. Here, we investigated the role of aluminum on carbonation of synthesized calcium aluminosilicate glasses with Al/Si ratio = 0.06 to 0.32 through carbonation at low and high water-to-solid ratios (w/s). Overall, Al/Si = 0.11 achieved the highest degree of carbonation (∼72%) while Al/Si ≥ 0.17 achieved the lowest degree of carbonation due to Al-rich regions requiring charge balancing by Ca 2+, thus leaving Ca 2+ forming Si-NBOs (nonbridging oxygen atoms) to participate in carbonation. Low and high w/s carbonation methods operated via distinct mechanisms, and high w/s carbonation produced a significantly higher degree of carbonation. To test their potential as supplementary cementitious materials, the pozzolanic reactivity of 24 h-high w/s carbonated glasses was tested; it increased with rising Al/Si ratio, which is an opposite trend to carbonation reactivity.