Molecular Dynamics-Based Study of Graphene/Asphalt Mechanism of Interaction
Round 1
Reviewer 1 Report (Previous Reviewer 3)
Comments and Suggestions for AuthorsAuthors responded to reviewer's comments properly. Thus, no more comments to authors.
Comments on the Quality of English LanguageN/A
Author Response
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Author Response.pdf
Reviewer 2 Report (Previous Reviewer 1)
Comments and Suggestions for AuthorsThe paper significantly improved therefore I am recommending for publication
Author Response
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Reviewer 3 Report (New Reviewer)
Comments and Suggestions for AuthorsThis manuscript reports on a molecular modeling study of composite materials associating graphene and asphalt components. The simulation protocols appear to be appropriate and the analysis of the results is comprehensive and globally convincing. This work is clearly valuable and deserves to be published. However, a number of points must be clarified/further justified:
- The interlayer distance between the graphene layers mentioned in the text (3.85 Å, line 125) is significantly different from the usual value of 3.35 Å. This difference should be justified.
- What is the typical size of the simulation box after equilibration (step 5) ? This is an important piece of information that is missing in the manuscript.
- Are the graphene layers allowed to bend during the MD simulations ? If so, is the bending smaller in the multilayers than in the monolayers ? Do the graphene multilayers tend to exfoliate during the MD simulations ? A comment should be added on those points.
- It is not reasonable to give solubility parameter values with three decimal digits (text on page 9 and Table 2). Are the changes brought by PGR (at most 0.1 (J/cm3)1/2) supposed to be significant when one sees the range of possible experimental values ? A comment must be added.
- In section 3.2.1, it is shown that the affinity between PGR and asphaltene depends on the number of graphene layers, peaking when two layers are present. However, no explanation is given for that observation. A (tentative) interpretation of those results must be added.
- In section 3.2.2, it is mentioned that no chemical reactions take place at the interface between graphene and the asphalt components. However, the force field used in the study is not appropriate to model chemical reactions, so the sentence on the absence of such reactions seems irrelevant. This must be clarified.
- Why is the interfacial binding energy increasing with the number of graphene layers (page 13) ? A explanation should be given.
- When modeling the healing process, the presence of the graphene layer in the middle of the gap inherently favors healing because of the van der waals interactions, which act in that range and attract the two asphalt sections towards each other. A better representation of the influence of graphene on healing would be to place the graphene layers WITHIN the asphalt sections. This is an important point, which must be addressed.
- Why is the presence of PGR enhancing the diffusion of asphalt molecules (page 18) ? Given the favorable interactions between those molecules and the PGR surface (section 3.2.2), one would expect that PGR slows down the diffusion. This must be clarified.
Technical points:
- The sentence “providing a specific reference value for the future large-scale application of graphene in asphalt pavements“ appears twice in the last paragraph of the introduction.
- In the models chosen to represent graphene on Fig. 5, there is an isolated carbon atom, which turns into a methane molecule upon saturation with hydrogen atoms. This seems awkward. Is that molecule present in the actual simulations ? This must be clarified.
- The same sentence appears twice at the beginning of section 2.2.
- In section 2.2.6, the diffusion coefficient seems to be represented by D and DC. Please use only one abbreviation.
- The expression “the amount of the power, line 361” is very strange and does not seem appropriate.
- In Table 3, it is not reasonable to give energy values in kcal/mol with three decimal digits.
- The expression “non-binding energy” should be replaced by “non-bonded interactions” (page 13).
- The expression “more incredible interfacial binding energy, line 398” seems strange.
- The title of section 3.2.3 is wrong.
To conclude, this manuscript should be accepted for publication when those points have been properly addressed.
Comments on the Quality of English LanguageMinor editing is required.
Author Response
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Author Response File: Author Response.pdf
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsPaper Title: Molecular dynamics-based study of graphene/asphalt mechanism of action
This paper uses molecular dynamics simulation to examine the mechanism of action of graphene-modified asphalt. The paper is well-written and quite interesting. However, a few concerns need to be addressed before the probable final acceptance. Following these comments, authors can modify their paper to enhance the quality of their manuscript:
1) Please check and correct the paper for typos, grammatical mistakes, and spelling mistakes. These were the few examples that I corrected them:
Please put ‘.’ at the end of the sentences in lines 29, 93 and 173. Also, finish the sentences appropriately.
The sentence in line 41: It has been proved... ‘proven’ should be used.
The sentence in line 100: The last comma in the sentence should be changed to ‘and’.
The sentence in line 115: … in Figure 2and Figure 3. Keep the space between 2 and ‘and’.
The article ‘the’ is not used in different parts or is wrongly used. Please revise that.
Please correct this sentence which needs the appropriate verb:
Molecular models of asphalt flank the healing model, and in the middle by molecular models of cracks or PGR, where the cracks are represented by a vacuum layer with a length of 20 Å in the OZ direction[15,23].
2) The introduction needs to be enriched with more recent (2023 and 2024) and related references. The authors only used one recently published paper from 2023!!!
Also, some studies have examined graphene plates based on theories. The authors must cite these references in their introduction:
https://doi.org/10.3390/mi14091790
https://doi.org/10.3390/mi14051052
https://doi.org/10.3390/math12081134
Moreover, Ref.23 has no publishing year, please correct it.
3) The authors used the software Materials Studio 2020 developed by Accelrys for the MD investigation. The simulation method needs to be explained more. It is better to use a separate part probably in the appendix and describe briefly more details about the simulation steps with related figures so that readers can understand the solution procedure more clearly.
4) Please correct the figure number of “Figure. 16 Graphene-modified asphalt mean..“, and it should be 15.
Also, in this figure, for example in (e) ACR modified asphalt, for the case 333K, why does its behavior act differently in higher times? (For example after about 50). The reasons for such extraordinary cases should be provided in the text.
5) What are some important applications of the study? Present them shortly in the last paragraph of the introduction section.
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
Comments and Suggestions for AuthorsThe theme proposed in the presented manuscript is of high practical importance; and can be of real interest for many applications. But the proposed manuscript requires serious improving.
Below one can find some remarks illustrating the above conclusion.
The title: "Molecular dynamics-based study of graphene/asphalt mechanism of action"
What is "…graphene/asphalt mechanism of action"? May be? Interaction
Line 37
What means: " having significant "small side effects," "quantum size effects," "surface and boundary effects"?
Line 121
The proposed algorithm by "…cutting graphite crystals, expanding crystal cells, and adjusting hydrogenation to construct molecular models of graphene with different sizes and numbers of layers,…" is unclear.
In the Section 2.1.4 "Construction of asphalt binder bulks" I see non-regular numeration 1 and 2 in circles, (i) and thereafter (iii)
Line 211
"The glass transition temperature (𝑇𝑔) is commonly used to characterize the temperature at which a material transitions from the viscoelastic to the glassy state." This sentence has no meaning.
The next sentence "Tg indicates the temperature at which molecular chain segments are frozen or begin to move." is incorrect from the physical point of view.
And the last sentence in this paragraph "For asphalt materials, the smaller the Tg, the higher the energy required for the asphalt molecules to move from the glassy to the viscoelastic state, and the better the low-temperature properties of the asphalt" is incorrect both in physical sense, and from the language point of view. The same incorrect sentence is repeated below in the beginning of section 3.2.3 Radial Distribution Function Analysis (line 367).
Line 218
I doubt that "the wetting" process is suitable as a mechanism in the system self-healing.
Line 235
The authors have written: "It is shown that the rms displacement is related to the molecular diffusion coefficient." But this fact is known for many years ago; and equations are the well-known definitions. Note that the above definition of diffusion coefficient is suitable only in the case of diffusive propagation type when the mean-square displacement is proportional to the first power of time.
The section "3.2.1 Radial Distribution Function Analysis" seems questionable. The point is that the Figures 9 and 10 demonstrate no regular behavior, declared in the text. In any case, it's very difficult to see the above regularities.
In the section "3.2.2 Bonding energy" (as well as in all text) it is necessary to choose only one definition: or "bonding energy", or "binding energy".
Line 464
The misprint: the figure number should be 15 in place of 16.
The section "3.2.5 Mean square displacement and diffusion coefficient" requires additional explanations.
First of all, the statement "Figure 15 shows that the MSD (root mean square displacement) of PGR-modified asphalt at different temperatures …, and increasing the test temperature increases the MSD value" contradicts to the regularities, presented in the plots (c), (d), and (e) of the Figure 15.
Further, the authors have written: "In the study, the MSD curves from 0 to 50 ps were analyzed, the MSD and simulation time were fitted in a double logarithmic manner, and the slope of the fitted straight line was defined as the free diffusion coefficient of asphalt molecules, D." Generally, it's correct, but in the manuscript no such plots (in double logarithmic scales) are presented. Moreover, only plots in double logarithmic scales are suitable in the case in question, as the presented data demonstrate non-diffusive motion character for the almost all simulation time; so, the determining of time intervals when the linear behavior of MSD is being observed, is necessary.
I can continue to indicate the points which are to be improved or seriously modified, but I prefer to stop. I believe that it's enough for conclusion that the possibility to publish the proposed manuscript can be considered only after serios revision.
In addition, the authors are using the modeling and simulation environment Materials Studio 2020. I doubt that industrial engineers to whom the manuscript is addressed, know what intermolecular interaction and other specific details on molecular level of considered material can be taken in to account; and what is outside of the program possibility. So, some discussions and explanations of such points are, in my opinion, very suitable.
Comments on the Quality of English LanguageThe follow sentence "For asphalt materials, the smaller the Tg, the higher the energy required for the asphalt molecules to move from the glassy to the viscoelastic state, and the better the low-temperature properties of the asphalt" can demonstrate the low English level.
Author Response
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Reviewer 3 Report
Comments and Suggestions for AuthorsIn this manuscript, authors performed MD simulation for understanding graphene/asphalt mechanism of action. Although it is interesting, there are certain parts that must be addressed:
1. Please offer the detailed process of choosing the graphene modification parameters and analyze it's influence on interactions between graphene and asphalt.
2. Experimental validation using atomic force microscopy / scanning electron microscopy to support the dispersion and morphology of graphene within the asphalt matrix is required. Also, durability test is necessary for long-term stability.
3. Please analyze the charge transfer effect inside the system using DFT calculations as well.
Comments on the Quality of English LanguageN/A
Author Response
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Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsI doubt that the modified manuscript version is really improved.
The corrections of some points are, in my opinion, formally and demonstrate a misunderstanding of basic principles.
For example, the mention of the quantum effects is absolutely unsuitable (although the authors did not describe the simulation protocol, I'm sure that no quantum calculations are included in the program).
The data for mean-square displacement, presented in the figures 19, did not correspond to a diffusive regime. To understand the regularity in molecular motion, I recommended to replot this data in double-log scale, but such a possibility to make clear the obtained data was ignored.
The added paragraph "3.2.6 Characterization of the interface morphology of graphene-modified asphalt" is absolutely unsuitable. Indeed, the scale in the presented SEM images is about of few micrometers, whereas the simulation scale is only few nanometers, i.e., 3 order of magnitude smaller. As the system in question are size-depending one, such a comparison is absolutely incorrect.
I believe that I indicated enough arguments for conclusion that the manuscript should be rejected.
Comments on the Quality of English LanguageIn this case (to reject the manuscript) it does not matter
Author Response
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Author Response File: Author Response.docx
Round 3
Reviewer 2 Report
Comments and Suggestions for AuthorsUnfortunately, I have to repeat my conclusion also regarding last manuscript version: I doubt that the modified manuscript version is really improved.
The corrections are, in my opinion, formally and demonstrate a misunderstanding of basic principles.
As an excellent example of this fact is the analysis of the data for mean-square displacement. According my recommendation, the data was replotted in double-log scale, but the authors did not understand (and, perhaps, do not know) why I ask to use such a presentation. No corresponding fitting was done; so, the authors cannot see that the presented data for mean-square displacement did not correspond to a diffusive regime, and diffusive coefficients, calculated by authors, have no physical meaning.
I see no reason for the further consideration of the manuscript containing such poor analysis of low scientific level; and I believe that it should be rejected.
Comments on the Quality of English LanguageThe English level is of no importance in this case
