Strengthening of Reinforced Concrete Structures with Carbon Reinforced Concrete—Possibilities and Challenges

Round 1

Reviewer 1 Report

This work shows the state-of-the-art of strengthening with carbon reinforced concrete in Germany. A strut-and-tie-model has been proposed to calculate the critical tensile force leading to failure. In addition, possible methods to avoid failure due to concrete cover separation are suggested, which should be useful to the practical engineering. Followings are some issues should be clarified.

Figure 1, what is the thickness marked in this figure?

If there is any regulation, standard or guideline for the use of CRC as a strengthening method that has been established in other countries, this should be presented.

Table 5, how many specimens have been tested? The scatter of data should be added.

Author Response

Thank you for your review report! We revised our manuscript according to the comments of all reviewers. Concerning your remarks, we did the following changes:

• Figure 1, what is the thickness marked in this figure?
  • It’s the required thickness of the strengthening layer of each strengthening method. An explanation was added in the figure caption.
• If there is any regulation, standard or guideline for the use of CRC as a strengthening method that has been established in other countries, this should be presented.
  • Internationally there are already some regulations. However, due to their large number, we decided to concentrate on the regulations in Germany in the paper. An additional sentence was added.
• Table 5, how many specimens have been tested? The scatter of data should be added.
  • There was only one specimen each, so there is no scattering. For clarification, Table 5 in section 5.1.1. was added.

Reviewer 2 Report

This paper provided a comprehensive review on strengthening of reinforced concrete structures with carbon reinforced concrete. The authors provided several actual projects of strengthening structures using carbon reinforced concrete. The challenges and developing directions are provided. Overall, the paper is well written. I have some comments here.

1. The authors should provide more technical details about those listed projects.
2.  What the reasons for failure in the bonding area of RC beams strengthened with carbon reinforced concrete?
3. The writing in Part 5 should be improved.
4. The authors did not describe the testing procedure clearly. More details are needed.
5. For Figure 20, please provide more explanation about the change of specimen 2.

Author Response

Thank you for your review report! We revised our manuscript according to the comments of all reviewers. Concerning your remarks, we did the following changes:

• The authors should provide more technical details about those listed projects.
  • Indeed, these projects are very interesting. However, in order to limit the length of the paper, we have deliberately omitted detailed information. The chapter is rather intended to give an overview of the possibilities of strengthening with CRC. Where available, references to further publications have been made in the individual sections. If necessary, we will also write a separate paper on CRC-strengthened structures.
• What the reasons for failure in the bonding area of RC beams strengthened with carbon reinforced concrete?
  • An additional sentence was added.
• The writing in Part 5 should be improved.
  • Part 5 was slightly revised. Could you please highlight the parts that need to be improved?
• The authors did not describe the testing procedure clearly. More details are needed.
  • All information on the testing procedure that we consider important are given in sections 5.1.3. and 5.1.4. Please let us know what further information you need.
• For Figure 20, please provide more explanation about the change of specimen 2.
  • The differences between specimen 1 and specimen 2 are described in sections 5.1.1. and 5.1.2.

Reviewer 3 Report

Very interesting work, however a few minor comments should be addressed as follow:

1- Results are missing in the abstract. Overall abstract must be rewritten to include, problem statement, aim/objective, methodology, results and recommendation.

2- More strengthening technique should be mentioned in the introduction such as (not limited) CFRP-strengthened ECC (10.1016/j.cscm.2019.e00327), CFRP plate (10.1016/j.istruc.2021.05.042), and 10.3390/ma13122804.

3- in the moment deflection curve (figure 20) it is recommended to not plot the defelction after 13.8 mm for specimen 2. Same goes to Figure 22, no need to show the unloading curve.

4- The conclusion is too long, it is recommended to make it in point form and focus on the focal findings.

Author Response

Thank you for your review report! We revised our manuscript according to the comments of all reviewers. Concerning your remarks, we did the following changes:

• Results are missing in the abstract. Overall abstract must be rewritten to include, problem statement, aim/objective, methodology, results and recommendation.
  • The abstract has been rewritten so that the objective and results of the research are more clearly highlighted.
• More strengthening technique should be mentioned in the introduction such as (not limited) CFRP-strengthened ECC (10.1016/j.cscm.2019.e00327), CFRP plate (10.1016/j.istruc.2021.05.042), and 10.3390/ma13122804.
  • In the introduction, other strengthening methods were included and related references were added
• in the moment deflection curve (figure 20) it is recommended to not plot the defelction after 13.8 mm for specimen 2. Same goes to Figure 22, no need to show the unloading curve.
  • The figures have been edited. However, the parts of the unloading curve in which significant forces could still be absorbed are intentionally shown in the diagram because they are characteristic of the failure mode.
• The conclusion is too long, it is recommended to make it in point form and focus on the focal findings.
  • The conclusions have been shortened.