Comparing the short-term leaching behavior of cements containing supplementary cementitious materials in different leachants for low-level waste encapsulation

Kozlowski, A. and Peshkur, T. and Renshaw, J. C. and Dobson, K. J. and Taylor, F. (2024) Comparing the short-term leaching behavior of cements containing supplementary cementitious materials in different leachants for low-level waste encapsulation. Geoenergy, 2 (1). 31. ISSN 2755-1725 (https://doi.org/10.1144/geoenergy2024-004)

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Abstract

Pulverised Fly Ash (PFA) is commonly used as a supplementary cementitious material (SCM) in cement and is permitted for use in cements and grouts used for the encapsulation of low-level nuclear waste. However, with a global decrease in availability of PFA predicted in the near future, alternative SCMs are required. In nuclear encapsulation, a key parameter for a new SCM is that it does not change the leaching behaviour of the grout. We present promising initial leaching data from two SCMs: Metakaolin and Waste Paper Fly Ash. These were tested for 24 hours in two leachants: deionised water and an artificial groundwater, tracking pH and leachability of a range of elements as the samples equilibrate with the leachants. The study suggests that for many elements, both Metakaolin and Waste Paper Fly Ash show very similar leaching behaviour to PFA grout formulations despite differences in the pH equilibration. In general, the tests suggest the composition of the elute is dominated by leaching from the cementitious phases, and not the SCM. This suggests further longer-term leaching studies are required as part of testing for SCM suitability for nuclear grouts, to understand the connections between leaching and grout microstructure.

ORCID iDs

Kozlowski, A., Peshkur, T., Renshaw, J. C. ORCID logoORCID: https://orcid.org/0000-0003-2073-3239, Dobson, K. J. ORCID logoORCID: https://orcid.org/0000-0003-2272-626X and Taylor, F.;
CORE (COnnecting REpositories)