Evolution in mechanical and microstructural properties of radioactive liquid organic waste-bearing alkali-activated slag under accelerated carbonation

This study examines the durability of alkali-activated slag (AAS) concerning carbonation resistance, incorporating Nevastane (NEV) and Shellspirax (SHE) as surrogates for radioactive liquid organic waste. The findings reveal that vaterite is the predominant CaCO3 polymorph formed in the AAS-based specimens, regardless of the presence of oil. Furthermore, the mechanical strength of the AASs incorporating oil (waste forms) remains stable under carbonation conditions. The degree of carbonation of these waste forms is significantly influenced by the type of oil, waste loading, and water-to-binder (w/b) ratio. Notably, waste forms containing NEV exhibit superior carbonation resistance compared to those containing SHE. The encapsulation of oil within AAS matrices adversely affects the pore structure development, and exposure to accelerated carbonation further coarsens the microstructure. AAS matrices show potential for the immobilization of challenging radioactive liquid organic waste. Given the significant impact of oil type on carbonation extent, further testing with relevant radioactive liquid organic waste is necessary to ensure the durability of the waste form against carbonation before its application in real-world scenarios.