The impact of cement on argillaceous rocks in radioactive waste disposal systems: A review focusing on key processes and remaining issues

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

“…In general, the dissolution of the primary minerals and the precipitation of secondary phases were observed over the first ~150 mm of the columns, which is similar to previous laboratory studies using crystalline rocks [9,10,12], in which a large zone of reaction was observed. This contrasts with experimental studies using sedimentary rocks [7,11,13,16] in which the extent of reactions was limited to only the first few millimetres, illustrating the difference in reactivity of the sedimentary versus crystalline rocks. However, it must be remembered that most experimental studies, including this one, used crushed samples with larger reactive surface areas and higher porosities than natural samples.…”

“…The chemistry of the migrating fluid will evolve over time, initially with high concentrations of both Na and K due to leaching of alkalis within the cement, resulting in a pH > 13 (Stage I), evolving to a Ca-dominated, portlandite-saturated fluid with pH ~12.5 (Stage II), followed by C-S-H buffering (Stage III), and finally returning to the natural background groundwater composition [5][6][7]. The evolving fluid chemistry will influence the long-term performance of the repository, altering the physical and chemical properties of the host rock, including radionuclide behaviour ( [7] and references within). Understanding these changes forms the basis for evaluating the long-term evolution of the repository.…”

“…The experiments described here document the use of sequential fluids to represent the evolution of the cement leachate fluid chemistry with time and distance, and how it interacts with the host rock, which has been identified as a key area of uncertainty, particularly with the modelling of such systems [7]. This was performed by setting up a series of identical column experiments to provide (at least in a laboratory time frame) information on the sequence of reaction.…”

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

“…The chemistry of the migrating fluid will evolve over time, initially being high in Na and K with high pH~13.5 (Stage I), evolving to a Ca rich fluid with pH~12.5 (Stage II), followed by C-S-H buffering (Stage III), and finally returning to the groundwater composition [7]. This evolving fluid chemistry will affect the long-term performance of the repository, altering the physical and chemical properties of the host rock, including radionuclide behaviour ( [7] and references within). Understanding these changes forms the basis for modelling the long-term evolution of the repository.…”

“…This study focused on the sequence of alteration owing to the evolution of OPC-type leachate chemistry on argillaceous mudstone from the Horonobe Underground Research Laboratory (URL), Hokkaido, Japan [19]. This study describes the use of sequential fluids to represent the evolution of the cement leachate fluid chemistry with time and how it interacts with the host rock, which has been identified as a key area of uncertainty, particularly with the modelling of such systems [7]. This was performed by setting up a series of identical flow experiments to provide (at least in a laboratory time frame) information on the sequence of reaction.…”