Reactive Transport Simulation of Low-pH Cement Interacting with Opalinus Clay Using a Dual Porosity Electrostatic Model
Round 1
Reviewer 1 Report
It would be good to give the mineralogical composition of cement with a low pH content in the article.
The article under consideration is devoted to the issues of modeling the reactive transfer with a of low-pH cement interacting with Opalinus Clay using a dual porosity electrostatic model. The purpose of the research is to show the prospects of using mixed cements, instead of Portland cement, in cement - Opalinus Clay systems used for the disposal of radioactive waste. Of value are modelling studies comparing different cement types interacting with clay under similar conditions to contribute to the engineering design of a repository.
Author Response
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Reviewer 2 Report
Very interesting topic. I suggest to include the fundamental characteristics of concrete and OPA also in this paper, even though these data were already published in the previous papers in the series describing the CI experiment.
The submitted paper deals with simulation of processes taking place at concrete-clay interface. It is very complex, but important topic.
The manuscript contributes to the field by interesting results. I suggest to present in this manuscript the composition of the used concrete (even though it was already published elsewhere). The same comment goes also for basic characteristics of Opalinus clay.
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Reviewer 3 Report
Minerals Manuscript #: 1207637
Review comments
Overall, the manuscript describes an interesting simulation study of the reaction and transport process between a low-pH cement and Opalinus Clay (shale). It is difficult to check the results of the simulation results, but I trust the authors’ work.
There are some suggested minor corrections that the authors need to address before the publication, which are further elaborated below:
Line 64-65: Advection in the compacted clays or shales may be small or negligible, and hence was ignored in this study. Could the authors provide some example data to compare the transport rate of ions via advection vs. diffusion? How about if the hydraulic gradient is high?
Line 65: clay hosted system -> clay host system;
Throughout the entire manuscript, the authors may need to use “past tense” to describe the work done.
Table 1: please provide a unit for the values
Lines 108-109: this sentence is not complete or grammatically wrong.
Chlorite and pyrophyllite were treated as inert by the authors. However, these two minerals are clays or have structure similar to clay minerals. If illite, smectite, and kaolinite are reactive, then these minerals may also be reactive.
Line 117, In general, clay sheets vs. clay layers have specific definitions and hence are different. Please change sheet to layer.
Line 116: total porosity contains … : Please change porosity into pores, and contain > contains. Porosity cannot be used with “contain”.
One key issue is the nucleation and reaction of clay minerals with alkaline or alkali. In fact, based on our own observation, clay-lime/NaOH reactions mostly started on the edge surface of a clay crystal, and then CSH or CAH or CASH nucleates and grows on these site. So the assumption that the Donnan pores contain no solid precipitates may not be correct.
Interlayer water vs. interlayer porosity: Interlayer water only exists in smectite or vermiculite or Sm and Vm-bearing mixed layers.
Figure 5: I could not understand the label for the horizontal axis.
Figures 6 and 7: the EDX elemental mapping images could be in color.
Overall the key issue is the nucleation site on clay particle surfaces. We have limited to support that nucleation actually initiates right on the clay mineral surface where Ca cations are adsorbed. The adsorbed cations may be the starting sites for crystal growth.
Finally, due to the cation exchanges, clay microstructure may change (such as aggregation and flocculation vs. dispersion), and hence the permeability may change. Could the model consider this aspect?
Line 322: improved > was improved
Author Response
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Reviewer 4 Report
Abstract must include numerical findings of the study
more inforamation and research must be provided in introduction
provide more information on "chemical and mineralogical changes at clay -
cement interfaces"
ESDRED provide full name and then use abbreviation
"The high Si content and lower pH in the porewater compared to OPC suppress portlandite formation" provşde more explanation to this
provide mpre information on "m-s-h formation and hat happen after this formation, what are the risk and how concrete affected from this formation?"
limitations of this study must be added
conclusions must be shortened
reccomendation section is missing and must be added
Author Response
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Round 2
Reviewer 4 Report
the necessary correction has been implemented in revised version
