Evolution of the Reaction and Alteration of Mudstone with Ordinary Portland Cement Leachates: Sequential Flow Experiments and Reactive-Transport Modelling

Autor:	Mitsuru Kubota, James Wilson, Yuji Ohuchi, Yuki Amano, Keith Bateman, Yuji Hanamachi, Takamasa Seta, Shota Murayama, Yukio Tachi
Rok vydání:	2021
Předmět:	reactive-transport modelling Cement Radionuclide Mineralogy Radioactive waste Geology radioactive waste disposal Aluminium silicate mudstone Geotechnical Engineering and Engineering Geology Chemical reaction law.invention ordinary Portland cement chemistry.chemical_compound Portland cement chemistry law Environmental science sequential flow experiment Leachate Groundwater QE351-399.2
Zdroj:	Minerals Volume 11 Issue 9 Minerals, Vol 11, Iss 1026, p 1026 (2021)
ISSN:	2075-163X
DOI:	10.3390/min11091026
Popis:	The construction of a repository for geological disposal of radioactive waste will include the use of cement-based materials. Following closure, groundwater will saturate the repository and the extensive use of cement will result in the development of a highly alkaline porewater, pH > 12.5 this fluid will migrate into and react with the host rock. The chemistry of the fluid will evolve over time, initially high [Na] and [K], evolving to a Ca-rich fluid, and finally returning to the groundwater composition. This evolving chemistry will affect the long-term performance of the repository, altering the physical and chemical properties, including radionuclide behaviour. Understanding these changes forms the basis for predicting the long-term evolution of the repository. This study focused on the determination of the nature and extent of the chemical reaction, as well as the formation and persistence of secondary mineral phases within a mudstone, comparing data from sequential flow experiments with the results of reactive transport modelling. The reaction of the mudstone with the cement leachates resulted in small changes in pH with the precipitation of calcium aluminium silicate hydrate (C-(A-)S-H) phases of varying compositions. As the system evolves, secondary C-(A-)S-H phases re-dissolve and are replaced by secondary carbonates. This general sequence was successfully simulated using reactive transport modelling.
Databáze:	OpenAIRE
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