Carbon dioxide sequestration by alkali-activated materials

The carbon dioxide (CO₂) sequestration (also referred to as “carbonation”) of alkali-activated materials (AAMs) as potential key components of future sustainable construction industry has been a research focus worldwide. Reaction products and microstructures of AAMs are different from ordinary Portland cement; therefore the carbonation mechanisms and assessments are different. This chapter mainly discusses the microstructural changes in alkali-activated slag mortars after carbonation and reviews factors influencing carbonation in alkali-activated systems, including precursors, activators, CO₂ concentration, and relative humidity. The compressive strength, main reaction products, porosity, and pore structure of AAMs before and after carbonation are investigated to improve the understanding of the characteristics and mechanisms of carbonation. There remains a large space to completely understand the carbonation in AAMs, yet the perspectives suggested in this chapter will be useful for future studies.