Property Improvement of Recycled Coarse Aggregate by Accelerated Carbonation Treatment under Different Curing Conditions

Round 1

Reviewer 1 Report

This manuscript tried to establish the best environmental parameter (relative humidity and CO2 concentration). The paper is well-written and this reviewer is recommending minor revision. The following comments are given to improve the quality of the manuscript.

1. Proofreading is suggested to improve the English Language of the manuscript to ensure better understanding. There are many long sentences.

2. The authors should justify why only 4 different curing conditions were applied.

3. From the Introduction, CO2 concentration ranged from 20 to 60%, why did the authors applied only 50% and 20%?

4. Similar to Q3, Relative humidity ranged from 40% to 70%, why were 50, 70 and 90% only applied in the study.

5. In Sections 3.1 and 3.2, the authors should state authoritatively the reasons for having the various results in all sub-sections (apparent density, water absorption, moisture content, e.t.c.)

6. The following are research papers related to this topic, I suggest benefiting from and citing them:

https://doi.org/10.1016/j.conbuildmat.2020.121940

https://doi.org/10.1016/j.conbuildmat.2019.04.231

https://doi.org/10.1016/j.cscm.2022.e01651

 

• https://doi.org/10.1080/23311916.2022.2122885

Author Response

Esteemed reviewer

We would like to appreciate your insightful and constructive comments on our manuscript. We have fully revised and improved the contents of our paper according to your suggestions. The explanations for your mentioned questions in our manuscript are as follows:

 

This manuscript tried to establish the best environmental parameter (relative humidity and CO₂ concentration). The paper is well-written and this reviewer is recommending minor revision. The following comments are given to improve the quality of the manuscript.

 

1. Proofreading is suggested to improve the English Language of the manuscript to ensure better understanding. There are many long sentences.

 

Response (R)  Esteemed reviewer, thank you very much for your constructive suggestion. We have already tried our best to proofread and revise the manuscript to improve the English language, Thank you very much for your suggestion, which is helpful to improve our manuscript.

2. The authors should justify why only 4 different curing conditions were applied.

3. From the Introduction, CO2 concentration ranged from 20 to 60%, why did the authors applied only 50% and 20%?

4. Similar to Q3, Relative humidity ranged from 40% to 70%, why were 50, 70 and 90% only applied in the study.

 

R  Esteemed reviewer, we would like to thank you very much for your question. In the introduction, it is indicated in the literature that the ideal CO₂ concentration for carbonation improvement is in the range of 20%-60% and the relative humidity is in the range of 40%-70%. Based on the existing studies, we selected carbonation curing conditions with CO₂ concentration of 20%, 50% and relative humidity of 50%, 70% and 90%.In fact, it was originally intended that the CO₂ concentration and the relative humidity of the environment would be more finely divided, including: 20%, 30%, 40%, 50%, 60%, etc., and RH=40%, 50%, 60%, 70%, etc. However, according to the pre-experimental results, we found that the errors of CO₂ concentration and relative humidity control in the carbonation chamber were mostly in the range of ± 5~10 %, i.e., if the CO₂ concentration was set at 20%, the actual concentration range of it could be as high as 10%-30%. To avoid this situation, we finally selected the CO₂ concentration of 20% and 50% to carry out the accelerated carbonation experiment of RCA by optimizing the experimental conditions. The selection of relative humidity condition is also in the same way. In addition, the more important reason why we finally chose only four different accelerated carbonation curing conditions is due to the long duration of the experiment process by the standard carbonation method, and the large volume of work required to test the corresponding CRCA experimental data at each carbonation time. Hence, after a comprehensive consideration, we selected these four optimized experiment conditions from Table 2 in the paper to carry out the research work. All the authors of this paper sincerely entreat that you can accept our consideration for this question, thank you very much for your constructive suggestion.

5. In Sections 3.1 and 3.2, the authors should state authoritatively the reasons for having the various results in all sub-sections (apparent density, water absorption, moisture content, etc.)

 

R  Esteemed reviewer, we would like to thank you very much for your question. By summarizing and sorting out the original Sections 3.1 and 3.2, we added the Section of “3.3. Summary of CO₂ concentration and relative humidity on RCA performances improvement” in our revised manuscript, which is used to explain the reasons for the improvement of RCA performances such as apparent density and water absorption after accelerated carbonation in Sections 3.1 and 3.2, and to systematically summarize the discussion in Sections 3.1 and 3.2 into a concise concept. For details, please refer to section 3.3 of the revised version by using the red fonts. All the authors of this paper sincerely entreat that you can accept our consideration for this question, thank you very much for your constructive suggestion.

6. The following are research papers related to this topic, I suggest benefiting from and citing them:

 

https://doi.org/10.1016/j.conbuildmat.2020.121940 

 

https://doi.org/10.1016/j.conbuildmat.2019.04.231

 

https://doi.org/10.1016/j.cscm.2022.e01651

 

https://doi.org/10.1080/23311916.2022.2122885

 

R  Esteemed reviewer, thank you very much for your constructive suggestion. After reading these four literatures, we found that they are indeed relevant to this paper, and we have referred to and cited the relevant literature in this paper. Thank you very much for your constructive suggestion.

 

What is said above are the entire responses about all your questions, and we greatly appreciate your thorough review and hope that this revised new manuscript in its present form will be acceptable for publication at Sustainability, thank you and best wishes. 

Sincerely yours,

  Mingjie Gu on behalf of all the authors

Author Response File: Author Response.pdf

Reviewer 2 Report

-        The manuscript explores the use of carbonated recycled aggregates and its impact on the performance of concrete. It claims to report the optimum carbonation conditions that bring an improvement in the physical properties of recycled aggregates. Accordingly, rapid carbonation is suggested to improve the water absorption and apparent density of recycled aggregates. However, unlike the description of the title, nowhere does it tell about the performance of the aggregates. Indeed, the carbonation parameters are optimized and an improvement in the property of recycled aggregates is achieved but their performance is not yet tested. To make it a complete article, my recommendation is that either the performance of these aggregates should be evaluated (in a mix design of concrete) or the title shall be changed to reflect what is inside the article.  

 

- In the Materials and experiments section, C40 concrete samples are prepared and then crushed to get the recycled aggregates. But you have not indicated the age of the concrete when you crush it (after 1 month or 3 months or… ?). How do you justify this may not be the case with recycled aggregates from end-of-life? Such argumentation shall be shown in your discussion part.  

-        Discussion results seem to have repetitive and with similar intentions. While the message is simple, you seem to bring the same message through another argumentation. You have to address it by systematically summarizing your discussion into compact and concise concepts.  

Other minor comments are described as follows:

1.      Line #60, How do you justify or relate carbonation can reduce (save) the use of energy in the building sector?  

2.      Other tests such as LA –abrasion test and aggregate crushing value (ACV) tests could tell a lot about improvement in performance. Without having aggregate performance indicators, it is difficult to talk about the increment in the performance of CRCA.   

3.      Line #134, “… initial water content of 0 from the original concrete…” what does this figure mean? Moisture or … ?

4. In Figure 2, it is hardly possible to differentiate NCA and RCA in the picture. When zoomed, it is difficult to see old mortar on RCA. Check these pics!

5.      Line #215, why do you need to titrate aggregates? Do you get any quantitative data? What is the added value of titration here? If you also spray a phenolphthalein solution on aggregates, it can give you qualitative information. If you mention titration, then you should be able to quantify the amount of CO2 absorbed per mass of aggregates.  

6.      Line# 246, “whereas the water absorption for the NCA is only 6.18% account for the RCA” is not a clear message, and try to rephrase it. Besides, Table 3 indicates water absorption of 5.33. How do you relate the above sentence with the value in table 3?

 

7.       The way numbers are reported is confusing. For instance … in line# 372, ‘NCA water absorption is about 7.20%, 8.20%, and 7.90% account for the CRCA under the carbonation curing conditions.’ This is difficult to understand, you could use a simple comparison to make it clear.      

Author Response

Esteemed reviewer

We would like to appreciate your insightful and constructive comments on our manuscript. We have fully revised and improved the contents of our paper according to your suggestions. The explanations for your mentioned questions in our manuscript are as follows:

 

1. -The manuscript explores the use of carbonated recycled aggregates and its impact on the performance of concrete. It claims to report the optimum carbonation conditions that bring an improvement in the physical properties of recycled aggregates. Accordingly, rapid carbonation is suggested to improve the water absorption and apparent density of recycled aggregates. However, unlike the description of the title, nowhere does it tell about the performance of the aggregates. Indeed, the carbonation parameters are optimized and an improvement in the property of recycled aggregates is achieved but their performance is not yet tested. To make it a complete article, my recommendation is that either the performance of these aggregates should be evaluated (in a mix design of concrete) or the title shall be changed to reflect what is inside the article.

 

Response (R)  Esteemed reviewer, we would like to thank you very much for your question. The research object of this paper is recycled coarse aggregate (RCA), focusing particularly on the improvement of the basic physical performances of RCA with accelerated carbonation of CO₂. This paper has not involved research works related to the effect of carbonated recycled aggregates on its concrete performances. In this paper, the apparent density, water absorption, and carbonation ratio are used as the basic physical performances of RCA to characterize the basic physical performances of RCA before and after carbonation and the degree of improvement of RCA performances by accelerated carbonation. Due to the fact that our paper focuses on RCA as the object and carries out the research work related to the carbonation improvement of RCA. After a comprehensive consideration and analysis, our authors still consider that the original title of the paper can be maintained. All the authors of this paper sincerely entreat that you can accept our consideration for this question, thank you very much for your constructive suggestion.

 

2. -In the Materials and experiments section, C40 concrete samples are prepared and then crushed to get the recycled aggregates. But you have not indicated the age of the concrete when you crush it (after 1 month or 3 months or… ?). How do you justify this may not be the case with recycled aggregates from end-of-life? Such argumentation shall be shown in your discussion part.

 

R  Esteemed reviewer, we would like to thank you very much for your question. The age of the concrete used for the preparation of RCA in this paper is 28 days. The corresponding contents have been revised using red fonts in Section 2.1 of our revised manuscript, thank you for your reminder and suggestion. For this paper”s study, the fresh concrete was cured for 28 days under standard laboratory conditions and crushed to produce the RCA used in the accelerated carbonation experiment. Theoretically, the whole performance aspects of fresh concrete are better than those of end-of-life concrete. If using the accelerated carbonation can improve the initial performance of RCA produced by fresh concrete to varying degrees, then for RCA prepared from end-of-life concrete, the accelerated carbonation should be able to improve its performance to a greater extent. In addition, there have been numerous scholars who have used the RCA prepared from fresh concrete with a curing age of 28 days in the laboratory after crushing and screening to investigate scientific issues related to RCA, which shows that this approach is feasible and commonly used in the field of research on RCA. In sum, this paper used the RCA prepared from fresh concrete cured at standard 28 days to explore the effect of accelerated carbonation on the degree of performance improvement, which should be regarded as a reasonable way. All the authors of this paper sincerely entreat that you can accept our consideration for this question, thank you very much for your constructive suggestion.

 

3. -Discussion results seem to have repetitive and with similar intentions. While the message is simple, you seem to bring the same message through another argumentation. You have to address it by systematically summarizing your discussion into compact and concise concepts.

 

R  Esteemed reviewer, we would like to thank you very much for your question. By summarizing and sorting out the contents of the original Sections 3.1 and 3.2, we have added the section of “3.3.Summary of CO₂ concentration and relative humidity on RCA performances improvement” in our revised manuscript to systematically summarize the discussion in this paper into concise and comprehensive concepts, as detailed in the red fonts of Section 3.3 in our revised manuscript. All the authors of this paper sincerely entreat that you can accept our consideration for this question, thank you very much for your constructive suggestion.

 

4. Line #60, How do you justify or relate carbonation can reduce (save) the use of energy in the building sector?

 

R  Esteemed reviewer, we would like to thank you very much for your question. Through the alkali aggregate characteristics of recycled aggregates to solidify carbon dioxide in the environment, energy conservation and emission reduction can be achieved. In accordance with your suggestion, we have further added to literatures of [25-27] in this area and also interpreted the literature related to carbonation reducing (saving) energy use in the building industry in our revised manuscript. All the authors of this paper sincerely entreat that you can accept our consideration for this question. Thank you very much for your questions, which are very helpful in improving our manuscript.

 

25. Pavlu, T.; Koci, V.; Hajek, P. Environmental Assessment of Two Use Cycles of Recycled Aggregate Concrete. Sustainabil-ity-Basel. 2022, 11, 6185.
26. Xian, X.; Logan, C.; Shao, Y. Dimensional stability of cement paste and concrete subject to early-age carbonation curing. Sustainability-Basel. 2022, 55, 94.
27. Long, W.J.; Zheng, D.; Duan, H.B.; Han, N.; Xing, F.; Performance enhancement and environmental impact of cement composites containing graphene oxide with recycled fine aggregates. J. Clean. Prod. 2018, 194, 193-202.

 

5. Other tests such as LA –abrasion test and aggregate crushing value (ACV) tests could tell a lot about improvement in performance. Without having aggregate performance indicators, it is difficult to talk about the increment in the performance of CRCA.

R  Esteemed reviewer, we would like to thank you very much for your question. In this paper, the physical performances of RCA and CRCA is mainly characterized by three indicators: carbonation ratio, water absorption and apparent density, the actual indicators related to crushing value test and wear test are not considered and involved at this stage, but we will further explore and analyze the indicators and suggestions mentioned by you in the subsequent study. Thank you for your valuable suggestions.

 

6. Line #134, “… initial water content of 0 from the original concrete…” what does this figure mean? Moisture or … ?

R  Esteemed reviewer, we feel very sorry about this issue. The initial moisture content of 0 in this paper refers specifically to the sample of RCA. We apologize for the misunderstanding of this concept due to our improper presentation of the English language in the original manuscript. We have revised the sentence in the revised manuscript: “RCA samples with the particle diameter of 10-20 mm and the initial water content of 0 produced based on the original concrete with strength grade of C40 with 28 days curing age after crushing and screening were prepared”, as detailed in the purple fonts section in Chapter 1 of the revised manuscript. All the authors of this paper sincerely entreat that you can accept our consideration for this question, thank you very much for your constructive suggestion.

 

7. In Figure 2, it is hardly possible to differentiate NCA and RCA in the picture. When zoomed, it is difficult to see old mortar on RCA. Check these pics!

 

R  Esteemed reviewer, we feel very sorry about this issue, and we have already improved the Figure 2 in our revised manuscript, thank you very much for your constructive and insightful suggestions.

 

8. Line #215, why do you need to titrate aggregates? Do you get any quantitative data? What is the added value of titration here? If you also spray a phenolphthalein solution on aggregates, it can give you qualitative information. If you mention titration, then you should be able to quantify the amount of CO2 absorbed per mass of aggregates.

 

R  Esteemed reviewer, we feel very sorry about this issue. This is indeed due to the mistake in our language. By spraying phenolphthalein solution on the surface of RCA and CRCA, combined with the color development reaction of alkali aggregates to characterize the reduction of alkalinity of RCA after accelerated carbonation, the performance of CRCA was qualitatively judged to be enhanced to a certain extent. Therefore, we have replaced “titrated” with “sprayed” in our revised manuscript, which is only a qualitative reflection rather than a quantitative representation, as detailed in the red fonts in section 2.2 of the revised manuscript. All the authors of this paper sincerely entreat that you can accept our consideration for this question, thank you very much for your constructive suggestion.

 

9. Line# 246, “whereas the water absorption for the NCA is only 6.18% account for the RCA” is not a clear message, and try to rephrase it. Besides, Table 3 indicates water absorption of 5.33. How do you relate the above sentence with the value in table 3?

 

R  Esteemed reviewer, we would like to thank you very much for your question.”the water absorption for the NCA is only 6.18% account for the RCA” characterizes the water absorption of NCA as a percentage of the water absorption of RCA, which was obtained by dividing the water absorption of NCA of 0.33% by the water absorption of RCA of 5.34% in Table 3, and other similar results and linguistic expressions in the text were quantified according to the above method. All the authors of this paper sincerely entreat that you can accept our consideration for this question, thank you very much.

 

10. The way numbers are reported is confusing. For instance … in line# 372, “NCA water absorption is about 7.20%, 8.20%, and 7.90% account for the CRCA under the carbonation curing conditions.” This is difficult to understand, you could use a simple comparison to make it clear.

 

R  Esteemed reviewer, we would like to thank you very much for your question. The above results characterize the percentage of water absorption of NCA to water absorption of CRCA. It is calculated by dividing the water absorption of NCA by the water absorption of CRCA, which is the same as the calculation of the results in Q9. For instance, 7.20% is obtained by dividing the water absorption of NCA by the water absorption of CRCA (CC-2) in Figure 10, i.e., (0.33% ÷ 4.565%) × 100% = 7.20 %, and other results are calculated in exactly the same way. All the authors of this paper sincerely entreat that you can accept our consideration for this question, thank you very much.

 

What is said above are the entire responses about all your questions, and we greatly appreciate your thorough review and hope that this revised new manuscript in its present form will be acceptable for publication at Sustainability, thank you and best wishes.

 

Sincerely yours,

  Mingjie Gu on behalf of all the authors

Author Response File: Author Response.pdf

Reviewer 3 Report

The author explored the recycled coarse aggregate by carbonation treatment; the research is very valuable, solid waste reuse, carbon dioxide reuse, and the scope are suitable for sustainability. However, there are some problems in experimental analysis and writing. The relevant analysis of the products generated after carbonation is lacking, which is a major flaw in the experimental content, and it is recommended to add relevant analysis content. And it is recommended major revisions are.

Abstract: In lines 11-12, the fundamental performance needs to be elaborated.

The abstract is too long. It should be revised to provide more results to highlight the novelty and significance of this study. 

Line 31-34, after carbonation, have specific properties improved? It needs to elaborate.

In the Introduction, the authors describe many ways to improve the basic performance of RA, but do not give the disadvantages of these methods.

Why is carbonization of RCA effective in improving its performance? Please explain from the principle.

Line 39-40, First of all, it is necessary to introduce the impact of construction material waste on the environment and society. Secondly, the significance of the dual-carbon strategy can be introduced to highlight the value of this research. These two kinds of literature can be referred to (https://doi.org/10.1016/j.jobe.2022.104880, https://doi.org/10.1016/j.conbuildmat.2022.126921); therefore, as we carry out this research work, the benefits to the environment and society must be elaborated.

Line 132-143, elaborate on why you want to study this research. What is the value of this work?

In line 248, What is the "OITZ"?

For Fig.15, What is the significance of building a model? Please elaborate on it.

For conclusion part, looking forward to the application value of this research work is necessary.

In this paper, the author mainly studied the properties of recycled aggregate. In fact, now the research of intelligent aggregate is also a developing trend. The author may refer to and cite the following related articles as well.

 

Embedded PZT aggregates for monitoring crack growth and predicting surface crack in reinforced concrete beam, Constr. Build. Mater. 364 (2023) 129979, 10.1016/j.conbuildmat.2022.129979.

Author Response

Esteemed reviewer

We would like to appreciate your insightful and constructive comments on our manuscript. We have fully revised and improved the contents of our paper according to your suggestions. The explanations for your mentioned questions in our manuscript are as follows:

 

1. The author explored the recycled coarse aggregate by carbonation treatment; the research is very valuable, solid waste reuse, carbon dioxide reuse, and the scopes are suitable for sustainability. However, there are some problems in experimental analysis and writing. The relevant analysis of the products generated after carbonation is lacking, which is a major flaw in the experimental content, and it is recommended to add relevant analysis content. And it is recommended major revisions are.

 

Response (R)  Esteemed reviewer, thank you very much for your significant comments. This paper took the recycled coarse aggregate (RCA) as the case. By analyzing the performance index changes of RCA, i.e. apparent density, water absorption, mass variation and carbonation ratio etc., the improvement of RCA performance under different accelerated carbonation curing conditions was explored, and the best accelerated carbonation curing conditions for RCA were obtained. In the subsequent research work, the preparation of recycled concrete using carbonated recycled aggregates and the analysis of the effect of carbonated recycled aggregates on the performance improvement of recycled concrete will be the next research focus, and our team strives to disclose the relevant research results as soon as possible. All the authors of this paper sincerely entreat that you can accept our consideration for this question, thank you very much for your constructive suggestion.

 

2. Abstract: In lines 11-12, the fundamental performance needs to be elaborated.
3. The abstract is too long. It should be revised to provide more results to highlight the novelty and significance of this study.
4. Line 31-34, after carbonation, have specific properties improved? It needs to elaborate.

 

R  Esteemed reviewer, we have revised the relevant issues in the abstract, including the basic performances of RA, the innovation and importance of this paper, and the specific degree of performance improvement of RCA after carbonation, all of which have been elaborated. The details have been refined in the "Abstract" of our revised manuscript using red fonts. Thank you very much for your constructive suggestion.

 

5. In the Introduction, the authors describe many ways to improve the basic performance of RA, but do not give the disadvantages of these methods.

 

R  Esteemed reviewer, thank you very much for your constructive suggestion. According to your suggestion, we have added further disadvantages about these methods to improve the basic performances of RA in the latest revised manuscript. The standard carbonation method has long carbonation reaction time and low carbonation efficiency; the pressurized carbonation method can improve the carbonation efficiency compared with the standard carbonation method, but it is difficult to quantify and refine the pressure control, and the excessive pressure may damage the aggregate and affect the carbonation modification effect of RCA; the flow-through CO₂ curing method requires higher carbonation technology and implementation cost than other methods; The water-CO₂ cooperative curing method requires strict control of the phase state and ratio of water vapor and CO₂, otherwise the carbonation effect is poor. The details have been refined in the “1. Introduction” of our revised manuscript using blue fonts. All the authors of this paper sincerely entreat that you can accept our consideration for this question, thank you very much for your constructive suggestion.

 

6. Why is carbonation of RCA effective in improving its performance? Please explain from the principle.

 

R  Esteemed reviewer, we would like to thank you very much for your question. Considering that the useful components of old mortar and OITZ for RA, including the Ca(OH)₂, C-S-H, C₃S, C₂S, etc., can undergo the chemical reactions with CO₂, subsequently, the generated dense CaCO₃ and silica gel (SiO₂-nH₂O) can further increase the solid phase volume of old mortar and OITZ for RA, densify the internal pores, and enhance the microstructure of RA, which can effectively improve the fundamental performances of RA. The chemical equations for aforementioned reaction process are as Ca(OH)₂ + CO₂ + CO))₃ + H₂O and C-S-H + CO₂  and C₃ + SiO₂·+ ₂O. Hence, the modification method of active carbonation for RA by using CO₂ can contribute to improve the physical and mechanical performances of RA based on the aforementioned chemical principles. The details have been improved in Section "1. Introduction" by using the rose red fonts of our revised manuscript. All the authors of this paper sincerely entreat that you can accept our consideration for this question.Thank you very much for your question, which is helpful to improve our manuscript.

 

7. Line 39-40, First of all, it is necessary to introduce the impact of construction material waste on the environment and society. Secondly, the significance of the dual-carbon strategy can be introduced to highlight the value of this research. These two kinds of literature can be referred to (https://doi.org/10.1016/j.jobe.2022.104880,https://doi.org/10.1016/j.conbuildmat.2022.126921); therefore, as we carry out this research work, the benefits to the environment and society must be elaborated.

 

R  Esteemed reviewer, thank you very much for your significant comments. As you suggested, we have referred to these two literatures to complement the environmental and social impacts of construction material waste and introduce the importance of the dual-carbon strategy. The details have been refined in Section “1. Introduction” of our revised manuscript by using green fonts. Thank you very much for your question, which is helpful to improve our manuscript.

 

8. Line 132-143, elaborate on why you want to study this research. What is the value of this work?

 

R  Esteemed reviewer, thank you very much for your question. Through the research of this paper, a feasible and green modification technology is provided for the application of recycled aggregates in practical engineering, which can effectively realize the saving and intensification of waste resources and the capture and utilization of carbon dioxide. It is consistent with the national development concept of energy conservation, emission reduction and green environment protection, and follows the national dual carbon policy strategic objectives. On the basis of your suggestions, we have further complemented the significance and value of the conducted research work in the latest revision. The details have been refined in Section “1. Introduction” of our revised manuscript using orange fonts. Thank you very much for your question, which is helpful to improve our manuscript.

 

9. In line 248, What is the "OITZ"?

 

R  Esteemed reviewer, thank you very much for your question. In line 248, OITZ refers to the old interfacial transition zone of recycled aggregates. For this abbreviation, we have explained it in Section "1. Introduction" of our revised manuscript by using yellow background fonts, We would appreciate if you could review it again. Thank you very much for your question and careful reminder.

 

10. For Fig.15,What is the significance of building a model? Please elaborate on it.

 

R  Esteemed reviewer, thank you very much for your question. the main purpose of the model is to quantitatively describe the variation pattern of CRCA performance indexes with carbonation time under the optimal carbonation curing conditions of CC-3 for the specific RCA in this paper, and to quantitatively calculate the performance parameters of CRCA under any carbonation time of accelerated carbonation curing conditions of CC-3.The details have been refined in Section 3.4 by using the red fonts of our revised manuscript. All the authors of this paper sincerely entreat that you can accept our consideration for this question, thank you very much for your constructive suggestion.

 

11. For conclusion part, looking forward to the application value of this research work is necessary.

 

R  Esteemed reviewer, thank you very much for your constructive suggestion. Through the research of this paper, a feasible and green modification technology is provided for the application of recycled aggregates in practical engineering, which can effectively realize the saving and intensification of waste resources and the capture and utilization of carbon dioxide. It is consistent with the national development concept of energy conservation, emission reduction and green environment protection, and follows the national dual carbon policy strategic objectives. Based on your suggestions, we have further complemented the application value of the research work in the conclusion section in the latest revision. The corresponding contents we have already supplemented in Section “4. Conclusions” in our revised manuscript by using the red fonts. Thank you very much for your suggestion, which is helpful to improve our manuscript.

 

12. In this paper, the author mainly studied the properties of recycled aggregate. In fact, now the research of intelligent aggregate is also a developing trend. The author may refer to and cite the following related articles as well.Embedded PZT aggregates for monitoring crack growth and predicting surface crack in reinforced concrete beam, Constr. Build. Mater. 364 (2023) 129979, 10.1016/j.conbuildmat.2022.129979.

 

R  Esteemed reviewer, thank you very much for your constructive and insightful suggestions. For the intelligent aggregate aspect, we would like to combine it with recycled aggregates for future research. Based on your suggestion, the description of this section has been supplemented to the conclusion of the revised manuscript in red fonts, referring to and citing the literature you suggested.Thank you very much for your suggestion, which is helpful to improve our manuscript.

 

What is said above are the entire responses about all your questions, and we greatly appreciate your thorough review and hope that this revised new manuscript in its present form will be acceptable for publication at Sustainability, thank you and best wishes.

 

Sincerely yours,

  Mingjie Gu on behalf of all the authors

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Dear Authors,

- The manuscript deals with the improvement of the property of coarse recycled aggregates by carbonation. Indeed, carbonation improved the property of recycled aggregates but the performance is yet to be seen. There is a difference between property and performance. The title is a bit misleading. My recommendation is to remove the word "performances". 

- Can you use uniform comparison with numbers? for instance, on line #259, "On the basis of Table 3, the measured apparent density of NCA is about 1.1 times than that of the RCA with the constant particle diameter, whereas the water absorption of NCA is only 6.18% account for the RCA" ... the first sentence is quite clear because it uses a comparison of NCA and RCA, and thus the apparent density of NCA is 1.1 times that of RCA. whereas the second sentence (water absorption of NCA is only 6.18% account for the RCA) is difficult to understand. you have many similar sentences. please you may consider rephrasing them. For example, the water absorption of RCA is 16 times higher than that of NCA.  

 

Author Response

Esteemed reviewer

We would like to appreciate your insightful and constructive comments on our manuscript. We have fully revised and improved the contents of our paper according to your suggestions. The explanations for your mentioned questions in our manuscript are as follows:

 

1. -The manuscript deals with the improvement of the property of coarse recycled aggregates by carbonation. Indeed, carbonation improved the property of recycled aggregates but the performance is yet to be seen. There is a difference between property and performance. The title is a bit misleading. My recommendation is to remove the word "performances".

 

Response (R)  Esteemed reviewer, we would like to thank you very much for your question. On the basis of your recommendation, we have already used the “property/properties” to replace the original “performance/performances” in our second revised manuscript by using the red fonts. All the authors of this paper sincerely entreat that you can accept our consideration for this question, thank you very much for your constructive suggestion.

 

2. -Can you use uniform comparison with numbers? for instance, on line #259, "On the basis of Table 3, the measured apparent density of NCA is about 1.1 times than that of the RCA with the constant particle diameter, whereas the water absorption of NCA is only 6.18% account for the RCA" ... the first sentence is quite clear because it uses a comparison of NCA and RCA, and thus the apparent density of NCA is 1.1 times that of RCA. whereas the second sentence (water absorption of NCA is only 6.18% account for the RCA) is difficult to understand. You have many similar sentences. Please you may consider rephrasing them. For example, the water absorption of RCA is 16 times higher than that of NCA.

 

R  Esteemed reviewer, we would like to thank you very much for your question. We have already rephrased the corresponding expressions similar with “the water absorption of NCA is only 6.18% account for the RCA” as the “the water absorption of RCA is 16 times higher than that of NCA.” during our second revised manuscript by using the blue fonts. Thank you very much for your insightful and constructive suggestion.

 

What is said above are the entire responses about all your questions, and we greatly appreciate your thorough review and hope that this revised new manuscript in its present form will be acceptable for publication at Sustainability, thank you and best wishes. 

Sincerely yours,

  Mingjie Gu on behalf of all the authors

Author Response File: Author Response.pdf

Reviewer 3 Report

The author has seriously responded to all comments, the quality of the manuscript has been improved, and it is recommended to accept the current manuscript.

Author Response

Esteemed reviewer

 

1. The author has seriously responded to all comments, the quality of the manuscript has been improved, and it is recommended to accept the current manuscript.

 

Response (R)  Esteemed reviewers, thank you very much for your acceptance for our research works, thank you and best wishes.

 

 

Sincerely yours,

  Mingjie Gu on behalf of all the authors

Author Response File: Author Response.pdf