Incorporation of organic liquid waste in alkali activated mixed fly ash/blast furnace slag/metakaolin-based geopolymers

• A geopolymer formulation was developed for conditioning up to 40 %v. of oil. • Rheology of pastes was characterized to assess influence of additives and waste. • Formulation robustness was tested with respect to raw materials origin and quantity. • Compliance with a preliminary set of waste acceptance criteria was verified. • Suitability of the formulation to condition other RLOW was preliminarily evaluated. The solidification of liquid oils (Shell Spirax and Nevastane EP 100) used as simulants of radioactive liquid organic waste (RLOW) in a specifically developed mix fly ash, blast furnace slag and metakaolin based geopolymer was studied in the present work. The process consists of obtaining the geopolymer paste slurry, produced by dispersing the solid precursors in the aqueous alkaline solution, and then adding RLOW via direct incorporation into the slurry under mixing to create an emulsion, before the geopolymer hardens. Geopolymer/oil composites have been prepared with various oil content (10, 20, 30 and 40 %v.), and subsequently characterized to verify their compliance with basic waste acceptance criteria. The positive role of the addition of a superplasticizer, to improve the fluidity of the paste, the density, and the homogeneity of the structure of geopolymer hardened materials was also demonstrated. The mechanical and engineering properties of the pastes and of solidified materials have been verified via rheological measurements and compressive strength tests. The optimized reference formulation loaded with 30 %v. oil waste has been tested in terms of raw materials variability and mixing proportion as part of a robustness study. Finally, the possibility to incorporate in the developed formulation other surrogated RLOW (tributyl phosphate/dodecane (30/70) and Liquid Scintillation Cocktail) has been studied with promising results.