Metakaolin-based geopolymers for nuclear waste encapsulation

The UK nuclear industry has a significant and challenging stockpile of nuclear wastes, and geopolymers produced from activation of the calcined clay metakaolin offer a valuable alternative to Portland cement-based systems. The characteristics of different formulations of metakaolin-based geopolymers, reacted with sodium and potassium silicate, are therefore of interest. As preliminary steps, the compressive strength and rheology of some metakaolin geopolymer grouts have been studied. This work showed that a potassium silicate-based geopolymer binder, with a sufficiently high water content can be produced to be highly workable. These grouts have a shear stress of approximately 80 Pa at a shear rate of 110 s−1 and can achieve compressive strengths of up to 40 MPa after 7 days of curing. This study is to be expanded in future and compared to the results produced from further analysis performed on the chemical structure of the geopolymer, as well as the overall physical characteristics achieved, to support the immobilisation, incorporation and retention of metal and oil based nuclear wastes.