Degradation of alkali-activated slag subjected to water immersion

In this study, the impacts of tap water immersion on the pore solution, phase assemblages, gel chemistry and structure, and pore structure of alkali-activated slag (AAS) pastes were studied. AAS degrades under such condition and the potential mechanisms can be concluded as lower reaction rates, gel decomposition and carbonation. The leaching of Na+ and OH  at early stages hinders the reaction of slag, which leads to a slower formation of reaction products. Long-term leaching can result in gel decomposition after 90 d. Coarsened gel pores and capillary pores are both identified in water-immersed samples. Additionally, the leached Ca2+ can react with the dissolved CO2 in tap water to form calcium carbonate. A calcium carbonate layer is observed surrounding the paste while the inner matrix is free of carbonation. The insights provided by this paper contribute to understanding the behaviors and durability of AAS in underwater conditions.