Cementation of spent radioactive ion-exchange resin ashes using alkali-activated cements: Physicochemical and structural changes

Spent ion-exchange resins (IERs) constitute the major volume of solid radioactive wastes generated by the nuclear industry and Portland cement wasteforms exhibit limitations for their conditioning and storage. In this paper, an alternative approach is conducted involving the solidification of IER ashes (IERAs) through the use of “one-part” alkali-activated cements (AACs). Systems with different chemistry based on blast furnace slag (BFS) and metakaolin (MK) were formulated and the physicochemical and structural changes of the gel products after incorporating IERAS were investigated. The incorporation of the IERA reduced the amount of C-A-S-H and (N,C)-A-S-H products while changing the pore structure and microstructure, reducing the mechanical strengths of the cement matrices; these effects were more remarkable in the high BFS systems. New insights are elucidated on the microstructural changes of the gel phases and suggest that AACs with BFS/MK ratios of 25/75 and 50/50 are promising candidates for conditioning IERA wastes.