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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

Reviewer #1: Yes

Reviewer #2: Partly

Reviewer #3: Yes

Reviewer #4: Yes

Reviewer #5: Partly

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2. Has the statistical analysis been performed appropriately and rigorously? -->?>

Reviewer #1: Yes

Reviewer #2: N/A

Reviewer #3: No

Reviewer #4: No

Reviewer #5: N/A

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3. Have the authors made all data underlying the findings in their manuscript fully available??>

The PLOS Data policy

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: No

Reviewer #5: Yes

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4. Is the manuscript presented in an intelligible fashion and written in standard English??>

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: No

Reviewer #4: Yes

Reviewer #5: Yes

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Reviewer #1: 1- Although both MIP and NMR techniques were used for porosity characterization, the paper fails to rigorously reconcile the different pore size classification schemes inherent to these methods. The thresholds defining “harmless,” “slightly harmful,” and “harmful” pores are applied equally to both NMR and MIP outputs, despite their differing sensitivities and principles. A critical comparative calibration is needed, particularly when drawing mechanistic conclusions based on porosity proportions.

2- Figure 9 and the accompanying text suggest that an increase in water-cement ratio leads to a “more compact” pore structure based on the decreasing hysteresis loop area. This interpretation contradicts classical understanding, where increased w/c typically produces more porous structures. The decrease in hysteresis area could instead be a result of increased pore connectivity and larger average pore sizes, reducing capillary retention during desorption. This alternative explanation is not considered.

3- The SEM images presented in Figure 6 are used qualitatively to support trends observed in other analyses, but no image processing or quantification is provided. As a result, the SEM section adds limited scientific value and cannot substantiate microstructural claims quantitatively.

4- While the authors attempt to validate their COMSOL simulation model using water absorption data (Section 4), the agreement is shown only qualitatively via contour maps. No statistical or graphical comparison between simulation outputs and experimental absorption curves is offered. This limits the rigor and usefulness of the modeling section.

5- The correlation between porosity (as measured by NMR or MIP) and capillary water absorption is repeatedly emphasized, yet no regression analysis or fitting (e.g., linear, power-law) is provided to quantify these relationships. This omission weakens the claim that porosity directly governs water transport dynamics.

6- While the T2 relaxation times are reported, there is no conversion to pore size distribution using an appropriate model. Furthermore, the authors do not distinguish between bound water and free water peaks, which are critical for understanding transport and retention mechanisms.

7- From MIP, porosity increases with higher w/c ratios, but the proportion of highly harmful pores in paste is lower than in mortar and concrete despite having higher total porosity. This indicates inconsistency or misinterpretation in assigning pore categories. A clearer explanation or cross-validation between MIP and NMR data is needed.

8- Given the scope and content of this paper, it may benefit from considering the following related works:

https://doi.org/10.1007/978-3-031-69626-8_32

https://doi.org/10.1061/(ASCE)MT.1943-5533.0004528

https://doi.org/10.1016/j.matpr.2023.04.103

Reviewer #2: In general, this study is interesting and has the potential to significantly contribute to the field, making it in high demand by the journal's readers. However, there is a significant drawback to the entire manuscript—the presented data is a technical report and not a logically related study. The authors discuss the results obtained by different analysis methods, but the work has no logical coherence and is not scientifically sound. The authors should significantly revise the manuscript and give it a more logical scientific character.

1. It is necessary to clarify what method was used to determine the composition of the cement presented in Table 1

2. Figure 1 and the data presented in it do not carry a deep scientific load and the authors are advised to transfer this figure to the supporting information file. Similarly, Figures 2 and 11.

3. Why are the data in Table 3 presented without statistical processing?

4 The size scale in Figure 6 is unreadable, it needs to be improved.

5. The conclusion also looks like the conclusion of a technical report and not a research manuscript. It needs to be carefully revised

Reviewer #3: The manuscript ‘Research on the Mechanism of Pore Structure on Water Transportation in Cement-based Materials’ investigates the factors influencing the water transport in three different cement-based materials, that is, paste, mortar and concrete, using different experimental techniques and a simulation model. The authors find that porosity decreases by adding to the paste fine and coarse aggregates, making the material more resistant to erosive media and therefore influencing its durability. Furthermore, the water-to-cement ratio is a main factor in compacting the pore structure, an important phenomenon in water retention.

Although the topic is not new and some of the conclusions can be expected, the data shown are interesting and of good quality. The discussion of the results is supported by a numerical simulation model; the content of paragraph 3.5 concerning the absorption-desorption curves is fine. References are complete and updated.

I suggest to publish the paper after the authors have considered the following remarks:

- there is a difference in the linguistic style of the different parts, perhaps due to multiple handwriting. I suggest revising the text by homogenizing the language.

- lines 107-109: since for non-Chinese researchers can be difficult to find these Codes, can you provide a reference?

- line 117: in fact, figure 1d shows the cutting machine, not the samples.

- line 122: can the authors explain the procedure to dry the sample? Did they use the oven at 80°C as before?

- line 130: ‘…according to the standards formulated by the National Technical Committee of Physical Stoichiometry.’ Please, give a reference.

- line 144: ‘m denotes the weight…’: m denotes the mass, not the weight.

- line 168: please, specify the model of SEM used.

- line 170 and following: how was the pressurization achieved? At a constant rate or with other means (e.g. dynamic response)?

- line 177: the SEM and the test sample…: the MIP, not the SEM

- line 185: ‘The pore size measurement range was 0.00002 to 200 μm’: please, control the range: are you able to measure the pore size within 0.02 nm? The Bohr diameter of the hydrogen atom is 0.1 nm.

- line 185: ‘the SEM and the test sample…: the NMR, not the SEM.

- lines 195 and 372: analysis, not analize.

- line 205: in figure 3a, b and c, ‘the volume of mercury intrusion is greater than that of mercury extrusion.’ It seems the contrary: the intrusion lines are always below those of extrusion lines.

- lines 206-208: ‘trend of cumulative mercury intrusion volume reduction is P1 > P2 > P3, M1 > M2 > M3, and C1 > C2 > C3, while the cumulative mercury extrusion volume undergoes negligible change.’ Concerning intrusion, P1 < P2 < P3; furthermore, extrusion volumes are significantly different for P and C samples. Only for M samples they are very similar.

- line 234 and following: the notion of harmless and harmful pores (in relation to durability?) should be defined.

- lines 238 to 250: all the quoted numbers are in my opinion useless, since the proportions are already visible in figure j and k.

- line 290: 90dP: maybe 90 days for C etc.?

- line 296: apparently, a second peak is not visible from figure 4a in the range 6-3000 ms. Can you show it in an inset?

- line 299: ‘indicating that the larger the water-cement ratio, the more the pore size.’ Unclear statement: the larger the size? The higher the number of pores?

- lines 328-348: as noted for MPI (lines 238-250), it is useless to repeat the numbers already shown in figure 5. It makes the text rather confuse.

- line 414: ‘…saturation at 12000’: 12000 g/m^2. Please, specify the units.

- line 415: ‘and that of P3 at 18,000.’ In fact, from the figure it seems that both P2 and P3 saturate at almost 16000 g/m^2.

- line 417-418: ‘The water absorption of the specimens shows that the paste is greater than the mortar.’ Greater in what sense? Please, clarify the sentence.

- Figure 9: can the authors add the error bars? Particularly for C samples it should be useful, in order to support the claim that the area of hysteresis loop decreases by increasing the water-to-cement ratio.

- line 546: ‘When the water absorption time reaches 10 days…’ This is not shown in the figure.

Reviewer #4: This work presents experimental studies on water absorption/adsorption in paste, mortar, and concrete with three water-binder ratios, supported by CFD simulations. While the results are of potential interest to the civil engineering community, the manuscript is overly lengthy and reads more like a preliminary report than a ready-to-submit journal article. Therefore, it is not of sufficient quality to motivate publication for now.

My major/minor concerns are the following:

1. Sections 3.1–3.3 should be consolidated into a single subsection with side-by-side comparisons and a schematic diagram of pore evolution to enhance readability and synthesis.

2. The lengthy descriptive passages (e.g., Lines 232–268, 290–320, 325–368, 412–440) should be streamlined. Some observations could be replaced with schematics or summarized more concisely.

3. Avoid redundant subsections like "Analysis of the reasons" (Lines 258, 313)—integrate explanations directly into results.

4. The CFD simulation setup is not described in the Methods section, leaving readers unprepared for Section 4. Provide details on boundary conditions, meshing, and validation.

5. Equation (2) (Line 407) lacks derivation or citation. Justify its reasonable use and include a derivation in the Supporting Material.

6. Clarify the definition of A (water absorption surface area)—is this cross-sectional area or pore surface area? (Line 408)

7. Figure 3

7.1) It is hard to read the graphs due to inconsistent color and symbols. Let me pick P1 as an example for explanation. The intrusion-extrusion curves of P1 (Figure 3(a)) should be with the same color (black) and differentiate intrusion-extrusion with symbols/line styles. Also, use the same color for P1/M1/C1.

7.2) Figures 3(g-i): Clarify the y-axis unit for cumulative mercury volume.

7.3) Figures 3(j-k): What is the number in x-axis? Is it a sample code?

7.4) Check the consistency of figure information.

8. Lines 206-208: The authors should re-examine on the ranking of cumulative mercury intrusion volume and the explanation of cumulative mercury extrusion volume.

9. Line 105: The abbreviation of paste, mortar, and concrete should be specified here.

10. Table 1: Is chemical composition of cement in mass fraction or mass percentage?

11. Table 2: Capitalize “Superplasticizer”.

12. Line 130: Cite the source for the National Technical Committee of Physical Stoichiometry.

13. Lines 168-169, 177-178, 185-186: Please check the description.

14. Line 195: MIP analyze or MIP analysis?

Line 372: SEM analyze or SEM analysis?

15. Lines 216-220: The interpretation of mercury intrusion-extrusion behavior requires clarification. The claim that “The insignificant change in the cumulative mercury volume” contradicts the visible hysteresis in Figure 3. While the extrusion curve does not mirror the intrusion trend, the disparity itself is significant and should be discussed as evidence of pore entrapment or ink-bottle effects. Moreover, the assertion that pore connectivity is "stable" (i.e., non-deformable) lacks justification. MIP hysteresis alone cannot confirm this—connectivity could evolve due to mechanical deformation or expansion of pore.

16. Figure 5: number?

17. Lines 414-417: Unit of water absorption capacity?

18. Figure 7: Can we plot the graphs with x-axis of time (h)? I do not see the specific reason in the discussion why to select the square root of time in x-axis.

19. Figure 8: The authors have plotted the equilibrium absorption-desorption isotherms of water in cement-based materials. However, in determining the area of the hysteresis loop, increasing the number of data points for the hysteresis loop may improve accuracy. Moreover, the lower closure point of the hysteresis loop should not artificially be zero in typical. Therefore, I suggest that the authors add a greater number of points. Also, the area of the hysteresis loop can be better computed through numerical integration to reduce numerical truncation errors rather than the curve fitting with simple cubic equation at absorption and desorption branches.

20. The first conclusion (Section 5) is overly broad and states a well-known fact. Focus on specific findings from this study

Reviewer #5: Comments from Reviewer

Manuscript ID: PONE-D-25-11920_reviewer.pdf

Title: Research on the Mechanism of Pore Structure on Water Transportation in Cement-based Materials

The authors investigated the water transport mechanism in cement-based materials with different water-cement ratios. The influence of the pore structure, three types of specimens with different water-cement ratios (paste, mortar, and concrete) was investigated. The authors investigated capillary water absorption and isothermal adsorption-desorption water transport. Additionally, the pore changes and porosity were analyzed. The obtained results show that the water transport speed of the paste is greater than that of the mortar and concrete, which is in good agreement with the experimental results.

The current form's presentation of methods and scientific results is unsatisfactory for publication in the PLOS ONE journal. The article is interesting but poorly prepared. Some comments apply to the entire article. Please take this into account when making corrections. The minor and significant drawbacks to be addressed can be specified as follows:

Minor comments:

1. (See 2.2) 2.1. Raw Materials ---> 2.1. Raw materials

2. 2.3 Test Methodology ---> 2.3 Test methodology

3. Tab. 2. Superplasticizer ---> Superplasticizer

4. Line 144. Where ---> where

5. Tab. 3. humidness ---> Humidness

6. 5.conclusion ---> 5. Conclusion

Major comments:

1. Fig. 3, panels (a) – (c) Why were lower pressure measurements not performed for some samples?

2. The authors were interested in the range of pores up to 200 nm. Why did the authors not perform low-temperature measurements of nitrogen adsorption? Mercury porosimetry is a method that is burdened with error. A combination of these two methods would be very desirable.

3. All figures - axis descriptions. Sometimes titles start with a lowercase letter, and sometimes with an uppercase letter. Please standardize.

4. Fig. 6. Very poorly visible information about the resolutions.

5. Figs. 7 and 8. After the adsorption/desorption cycle, was another cycle of measurements performed on the same sample?

6. Tab. 4. Too high precision of the given values.

Sincerely,

The reviewer.

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

Reviewer #4: No

Reviewer #5: Yes:  Piotr A. Gauden

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<p>Research on the Mechanism of Pore Structure on Water Transportation in Cement-based Materials

PONE-D-25-11920R1

Dear Dr. Dali,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Kind regards,

Anwar Khitab

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

Reviewer #3: All comments have been addressed

Reviewer #4: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions??>

Reviewer #3: Yes

Reviewer #4: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously? -->?>

Reviewer #3: Yes

Reviewer #4: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available??>

The PLOS Data policy

Reviewer #3: Yes

Reviewer #4: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English??>

Reviewer #3: Yes

Reviewer #4: Yes

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Reviewer #3: (No Response)

Reviewer #4: The authors have partially responded my comments with reasonable facts from what they found. I thereby accept the current version of the revised manuscript.

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what does this mean? ). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy

Reviewer #3: No

Reviewer #4: No

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