Optimization of Fresh and Mechanical Characteristics of Carbon Fiber-Reinforced Concrete Composites Using Response Surface Technique

Round 1

Reviewer 1 Report

The manuscript is prepared in a really poor way. The formatting of tables, paragraphs, figures, equations, and many others makes it impossible to understand the overall merit of the manuscript. Moreover, the manuscript requires extensive English editing; many fragments are written in different tenses—once in the past tense, once in the present tense, etc.

The manuscript in its current form is not acceptable for publication.

Author Response

Thank you very much for reviewer for his valuable suggestions. We have attached reviewer response in the word file so kindly check it.

Author Response File: Author Response.docx

Reviewer 2 Report

This paper investigated optimization of fresh and mechanical characteristics of carbon fiber-reinforced concrete composites. A lot of work has been done and rich data results and related analysis have been obtained, which is important for promoting the application of carbon fiber in the concrete. To further improve the quality of the paper, the authors are encouraged to consider the following comments to make necessary improvements. 

1. In the abstract, it is suggested to further simplify the writing of research background and significance, and provide more qualitative and quantitative results and conclusion, for example, improvement mechanism, mechanical properties and failure modes, which information is important to readers.

2. The paragraph spacing between the second and fifth paragraphs of the introduction part is inconsistent with other paragraphs. It is suggested to make relevant adjustments.

3. The writing logic of the introduction part is somewhat confused. In paragraph 3, the authors should introduce common fillers for concrete, and the properties of relevant fillers. In this section, you should focus on summary of carbon fiber. After that, the summary of relevant research should be further corroborated.

4. For the introduction of carbon fiber, the authors should objectively analyze the advantages and disadvantages of carbon fiber. For example, the price of carbon fiber is very high compared to the other synthetic fiber, and the elongation at break is very low. Therefore, if it is used in concrete, some related problems (cost, brittle failure) need to be summarized. On the other hand, carbon fiber has higher mechanical properties, excellent water and alkali corrosion resistance, fatigue/loading resistance and high temperature resistances, which can improve the long-term performance and high temperature resistance of concrete structures. The latest research work on carbon fiber and its composite can justify the above comments and should be reviewed for the further supplement. Composite Structures, 2022, 293, 115719. Composites Part B: Engineering, 2019, 174: 106942. Polymer Composite, 2020, 41:5143-5155.

5. The relevance of Part 2 and Part 3 to this paper should be further clarified firstly. You can briefly explain it at the beginning of Part 2 and Part 3.

6. In part 4.3 (preparations of samples), it is better to provide a sample preparation physical diagram. The format of table 1 is incorrect, it should be a three-line table. It is recommended to make corresponding adjustments.

7. The authors are encouraged to check the figures and tables through the text, and supplement the relevant figure or table names and adjust the relevant format. In addition, standard deviation should be provided for relevant data, such as Figure 1, 2....

8. It can be seen from Figure 3 and Figure 4 that the addition content of carbon fiber seems to have no obvious effect on the compressive and tensile strength of concrete. Relevant data variation may be within the range of standard deviation. It is suggested to provide relevant explanations.

9. Please adjust the number of decimal places in the full text and keep consistent. For example, there are too many decimal points in the data in Figure 9. Is the decimal meaningful?

10. Conclusion should be further refined, including 3 to 4 key information points related to this paper.

Author Response

We appreciate to the reviewer for his good comments. We have attached the reviewer response so kindly check it.

Thank You

Author Response File: Author Response.docx

Reviewer 3 Report

This paper presents a methodology for the optimization of the design of carbon fiber-reinforced concrete using response surface technique. The reviewer recommends the authors address the following comments and revise the manuscript for a resubmission.

1. All abbreviations, such as SCC and NVC, should be explained.

2. The explanation of the response surface methodology is insufficient. Please clarify the function used as the response surface, and objective and explanatory variables.

3. Pictures and figures should be used in Section 5 to increase the reliability of the experimental results. 

4. Slump, workability, compressive and split-tensile strengths, water absorption, and acid attack resistance are investigated as the performance indicators of concrete specimens. Please describe the design values of each indicator. In addition, the differences between experimental and design values should be discussed.

5. Please describe why the compressive strength decreases when the ratio of carbon fiber is greater than 0.6.

6. Please explain the mechanism by which the water absorption increases as the amount of carbon fibers increases.

7. In Section 5.3: The amount of carbon fibers should be used as an explanatory variable in the regression analysis to investigate the its effect on the split-tensile strength. Otherwise, the it should be validated that the amount of carbon fibers does not affect the split-tensile strength.

8. In Section 5.5: Crack characteristics of each specimen should be presented to validate the experimental results of acid attack tests.

9. Please demonstrate the validity of Equation (1). Why is the 28-day compressive strength used as a variable in the equation (why are slump, workability, split-tensile strengths, water absorption and acid attack resistance ignored here?).

10. In Section 5.8: The validity of each result of regression analyses should be discussed based on the engineering evidences. In addition, the applicability and limitation of each regression result should be investigated.

11. The validity of the proposed methodology for the optimization of concrete mix design including carbon fibers is unclear. The estimation result of the optimization performed in Section 5.12.3 should be investigated by an experiment or numerical simulation.

Author Response

We appreciate to the reviewer for his good comments. We have attached the reviewer response so kindly check it.

Thank You

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

I'd like to express my gratitude to the authors for revising the manuscript. It is better; however, in my opinion, still some elements should be improved. The first and most important aspect is the quality of the presentation; still, the graphs, equations, etc. are not correctly formatted. Authors do not keep constant ratios between height and width of figures. The fonts of equations are different than the rest of the manuscript—different size, bolded, etc.

Secondly, the RSM is just a tool to achieve a given goal, not a scientific novelty itself. So there is no necessity to include all possible results generated by the Design Expert software in the main body of the manuscript. Most of it should be transferred to ESI (electronic supplementary information). Important elements of RSM are the experimental matrix, independent and response factors with their corresponding levels, polynomial equations for the respective response factors, and graphs such as response surfaces, etc. Finally, a table summarizing the results of optimization, i.e., optimal conditions, desirability, and comparison of actual and predicted value. You may also include statistical measures such as p-value and R2 to show the fit of the implemented optimization model; the rest of the ANOVA results are just a backend and should stay in ESI. Why? At this moment, your article is quite hard to read due to the enormous number of unnecessary tables and figures, so the main merit of your scientific work is just diluted and may be lost by the readers.

Author Response

Comment 1: I'd like to express my gratitude to the authors for revising the manuscript. It is better; however, in my opinion, still some elements should be improved. The first and most important aspect is the quality of the presentation; still, the graphs, equations, etc. are not correctly formatted. Authors do not keep constant ratios between height and width of figures. The fonts of equations are different than the rest of the manuscript—different size, bolded, etc.

Response: Thank you very much to the reviewer for his valuable suggestions to improve the quality of paper. This has been addressed in the manuscript.

Comment 2: Secondly, the RSM is just a tool to achieve a given goal, not a scientific novelty itself. So, there is no necessity to include all possible results generated by the Design Expert software in the main body of the manuscript. Most of it should be transferred to ESI (electronic supplementary information). Important elements of RSM are the experimental matrix, independent and response factors with their corresponding levels, polynomial equations for the respective response factors, and graphs such as response surfaces, etc. Finally, a table summarizing the results of optimization, i.e., optimal conditions, desirability, and comparison of actual and predicted value. You may also include statistical measures such as p-value and R2 to show the fit of the implemented optimization model; the rest of the ANOVA results are just a backend and should stay in ESI. Why? At this moment, your article is quite hard to read due to the enormous number of unnecessary tables and figures, so the main merit of your scientific work is just diluted and may be lost by the readers.

Response: This has been incorporated based on the reviewer suggestion.

Reviewer 2 Report

Accept.

Author Response

Thank You very much to the reviewer for accepting the manuscript. We have checked the English language and style through out manuscript. 

Reviewer 3 Report

The revised manuscript satisfactorily addressed the reviewer's comments and is recommended to be accepted.

Author Response

Thanks a lot to the reviewer for accepting the manuscript. 

Round 3

Reviewer 1 Report

Thank you very much for revising the manuscript. It can be accepted in current form.