Research on Capillary Water Absorption Characteristics of Modified Recycled Concrete under Different Freeze–Thaw Environments

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The submitted article can be published after minor corrections.

Some specific comments:

- line 82 - please correct the chemical formula - Na2SO4

- some images are hard to read. please improve the quality (eg. Fig 6, Fig 7, Fig 8-10) 

- please provide some information about SEM: equipment producer, detector, current/accelaration voltage.

- line 158 please use subscript in Ca(OH)2

- line  474 and line 461 - CSH gel or C-S-H gel?

- "a lot of chaotically arranged needle-like calcium alumina and gypsum 504 as well as sulfate crystals in the interfacial transition zone" - how can you be sure? Do you have some tests in order to confirm this conclusion? Can you include in the manuscript EDS spectra or microzone composition?

Author Response

Dear reviewer, Hello, thank you for your valuable comments on my article in your busy schedule, I have written the revised response in the document, I hope you can take the time to download and review, thank you!

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The focus of this paper is the durability of recycled concrete. The study uses concrete made from recycled coarse aggregate modified with water glass and silane solution. It examines the concrete's behavior under rapid freeze-thaw tests in different solutions (water, NaCl, and Na2SO4) followed by capillary water absorption tests. The research aims to establish a model to predict initial capillary water absorption under various freeze-thaw conditions and analyze the internal structure of the recycled aggregate concrete (RAC) using Scanning Electron Microscopy (SEM). The findings show that composite-modified water absorption is decreased, enhancing the durability of recycled concrete. The paper concludes that chloride salt has the most substantial erosive effect on recycled concrete, and the predictive model developed shows high accuracy for capillary water absorption experiments of recycled concrete.

The study is interesting and the paper is generally well-written. My comments on this work are as follows:

A discussion on the long-term durability of the modified recycled concrete under natural environmental conditions would be useful. The authors also need to provide an assessment of the environmental impact of using these chemical modifiers in recycled concrete. This could involve analyzing the lifecycle of the materials and their potential ecological footprint.

A comparative analysis of the modified recycled concrete with traditional concrete in terms of cost, performance, and sustainability would offer a clearer understanding of its practical applications and advantages.

I also suggest (if possible and available) that the authors consider a more detailed microstructural analysis using advanced techniques like X-ray diffraction or nuclear magnetic resonance to provide deeper insights into the changes in the concrete's internal structure post-treatment.

 

Finally, the authors need to comment on the application of the modified recycled concrete in real-world construction scenarios or larger-scale applications in the construction industry.

Comments on the Quality of English Language

The English of the paper is OK.

Author Response

Dear reviewer, Hello, thank you for your valuable comments on my article in your busy schedule, I have written the revised response in the document, I hope you can take the time to download and review, thank you!

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

 

 

Dear Authors, thank you for your manuscript, here will be following comments:

1. Abstract requires a bit of structural approach such as intro, problem & novelty, solution & conclusion.

2. in your introduction part you would also need to bring a structure with indication of problem, research objectives and overview of all info which leads to novelty of your study.

3. table 5, please provide volumes of all materials per 1m3 if concrete

4. Sub-section 2.3.1. please elaborate text more for the method applied in a way it has a clear structure of description. 

5. please provide surface photos for all 4 concrete mixes in figure 5 ( from Table 5) to see clear difference on frost-thaw cycling and solution impact on different mixes. 

6. the same remark for SEM images. Identification as RAC group is not clear about which mix you talk about. please be more specific in details in your description. Figures 11-12-13-14 about which mix you talk about?

in general please provide a full set of images for all mixes to have a clear distinction and comparison to have an idea how does modification of mixes with water glass and silane affects the freeze-thawing.

how many samples per serie tested? please provide stdev in your charts.

 

Comments on the Quality of English Language

ok

Author Response

Dear reviewer, 

Thank you for your valuable comments on my article despite your busy schedule. I have written a revised reply in the document. I hope you can take the time to download and review it. Thank you!

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have addressed my comments satisfactorily. I now recommend the manuscript for publication.

Author Response

Thank you very much for taking the time to review the paper again.

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors, please check following site https://www.statology.org/excel-plot-mean-and-standard-deviation/

you dont need to have a sub-section 3.2.6. but just error bars with srdev values on your charts

Figure 5 - still not clear which of the mixes was used for imaging

Comments on the Quality of English Language

ok

Author Response

Dear reviewer, hello, thank you for reviewing my manuscript again in your busy schedule, thank you very much for your valuable comments, I have been based on your valuable comments one by one to reply and modify, and made into a document, I hope to take up a little more of your valuable time to download and review again, thank you. I wish you good health and happiness every day!

Point 1. Dear Authors, please check following site https://www.statology.org/excel-plot-mean-and-standard-deviation/

you dont need to have a sub-section 3.2.6. but just error bars with srdev values on your charts

. Response 1: Thank you for your careful review and valuable comments. I have added STDEV to Fig. 6 because the pre-capillary absorption is the most influential, and I have deleted subsection 3.2.6. See Figure 6 in the text

Point 2. Figure 5 - still not clear which of the mixes was used for imaging

Response 2: Thank you for your careful review and valuable comments. I have added a new detailed annotation in subsection 3.1 that the RAC group is normal recycled concrete and marked in red; see subsection 3.1 in the text where it is marked in red