Round 1

Reviewer 1 Report

The manuscript “Life Assessment of Corroded Wire for Prestressing” presents very interesting research of the procedure for assessment of the characteristics of corroded wire for prestressed concrete. The steel elements investigated in this research are very common in use in civil constructions and other branches of industries. The methodology developed by authors for this purpose is explained in the paper and demonstrated on a case study. The methodology incorporates few verified methods but is basically oriented to implementation of the Theory of Critical Distances, and presents new application of this methods which become in focus in recent years. This manuscript can be considered for publications in Journal “Metals” if authors make few corrections in accordance with following remarks:

-        The Introduction part of the manuscript should be extended with the detail review of the main postulates of the Theory of Critical Distances with explanations of the already published applications. The authors need to give explanation of the contribution of the presented research in this context.

-        The Methodology for life assessment of corroded wire for prestressing, shown by the flow chart at Fig 1 need to be explain in detail within the part 1.

-        In part 2.1.2, table 3, the data regarding modulus of elasticity is missing. Elasticity modulus is the key parameter that determines force during prestressing of concrete.

-        The more detail explanation about the Finite element model needs to be given in the part 2.2. Especially, the chosen material model should be stated. The maximum value of the equivalent von Mises stresses shown at the contour plots for the results of FEA need to be reconsidered and explained.

Author Response

The manuscript “Life Assessment of Corroded Wire for Prestressing” presents very interesting research of the procedure for assessment of the characteristics of corroded wire for prestressed concrete. The steel elements investigated in this research are very common in use in civil constructions and other branches of industries. The methodology developed by authors for this purpose is explained in the paper and demonstrated on a case study. The methodology incorporates few verified methods but is basically oriented to implementation of the Theory of Critical Distances, and presents new application of this methods which become in focus in recent years.

# Thank you for very kind comment, as well as for very valuable suggestions that help us to improve the manuscript.

This manuscript can be considered for publications in Journal “Metals” if authors make few corrections in accordance with following remarks:

- The Introduction part of the manuscript should be extended with the detail review of the main postulates of the Theory of Critical Distances with explanations of the already published applications. The authors need to give explanation of the contribution of the presented research in this context.

# Thank you for your valuable comment. We’ve extended the introduction of the manuscript accordingly.

- The Methodology for life assessment of corroded wire for prestressing, shown by the flow chart at Fig 1 need to be explain in detail within the part 1.

# We’ve added the detail explanation of the Methodology for life assessment of corroded wire for prestressing, shown by the flow chart at Fig 1, as well as re-drawn Fig.1 to provide increased font size and make it more clear for the reader.

- In part 2.1.2, table 3, the data regarding modulus of elasticity is missing. Elasticity modulus is the key parameter that determines force during prestressing of concrete.

# Thank you very much for this remark. We’ve added the data for the experimentally obtained modulus of elasticity in the table 3.

- The more detail explanation about the Finite element model needs to be given in the part 2.2. Especially, the chosen material model should be stated. The maximum value of the equivalent von Mises stresses shown at the contour plots for the results of FEA need to be reconsidered and explained.

# Thank you for this very valuable comment for improvement of results’ presentation and discussion. We’ve added the information that the material model chosen for FEA is linear elastic material model, with the additional explanation of its correlation with the next step in the presented methodology. We’ve also re-organized the figures 12-14 in figure 12a-12c, and presented in the figures 11 and 12 the min-max stress values at the result contour-color bar for the zones with stress concentrator we analyze in this research. In these figures we’re excluding the local maximum stresses of the simulated model which is only the result of the simulation of tensile force at single node of the finite element model, and therefore they are not valuable for the discussion.

Reviewer 2 Report

This paper studied the use of the Theory of Critical Distances to determine the real properties of corroded wire in terms of evaluation of remaining load capacity. The topic is interesting and will appeal to readers in the structural health monitoring field. However, there are some problems; the author needs to explain them. It is recommended for major revision.

 

1.     In the lines33-34, General building materials are indeed challenging to meet the requirements of special projects such as bridges, so researchers have done a lot of research work, such as adding fibers and nanomaterials to strength and toughen, such as developing ultra-high-performance concrete for bridges and offshore wind turbine platforms. You can refer to:

https://doi.org/10.1016/j.jobe.2022.104880

https://doi.org/10.1016/j.conbuildmat.2022.126921

2.     In the introduction section, you should detail the current methods and the advantages of the methods your use. Highlight your innovations.

3.     In the “lines 53-64” of the Introduction Section, the authors only provided different methods but failed to give the benefits and weakness of different methods.

4.     In the Introduction, the authors should have added some other methods for assessing structural damage (i.e., PZT aggregates). This aspect can be better emphasized in the manuscript, e.g. by considering following literature

https://doi.org/10.1016/j.conbuildmat.2022.129979

5.     In the “lines 79-81”, how do you prove that the railway bridge you sampled used prestressed wire?

6.     In Figure 6, which section of the corroded wire is observed in the 3D profile using the microscope HIROX RH2200?

7.     Why are the sample numbers in Table 1 and Table 3 inconsistent?

8.     The tensile test results do not intuitively give the conclusion stated in "lines 135-136". Further explanation is requested.

9.     In the Theory of Critical Distances, why is half of the critical distance, namely L/2, adopted instead of L directly (As shown in “Lines 231-232”)?

 

10.  In this paper, Figure 15 is one of the most important figures, but the authors do not discuss it in detail.

Author Response

This paper studied the use of the Theory of Critical Distances to determine the real properties of corroded wire in terms of evaluation of remaining load capacity. The topic is interesting and will appeal to readers in the structural health monitoring field. However, there are some problems; the author needs to explain them. It is recommended for major revision.

# Thank you for your kind comment, as well as for very valuable suggestions that help us to improve the manuscript

1. In the lines33-34, General building materials are indeed challenging to meet the requirements of special projects such as bridges, so researchers have done a lot of research work, such as adding fibers and nanomaterials to strength and toughen, such as developing ultra-high-performance concrete for bridges and offshore wind turbine platforms. You can refer to:

https://doi.org/10.1016/j.jobe.2022.104880

https://doi.org/10.1016/j.conbuildmat.2022.126921

# Thank you for this remark. We’ve extended the introduction of the manuscript according the main topic of the presented research, i.e. steel wire for prestressed concrete which is already in exploitation. We emphasized in the manuscript that the one of the main advantages of the developed methodology is investigation of the steel elements already in use for long period.

 

2. In the introduction section, you should detail the current methods and the advantages of the methods your use. Highlight your innovations.

# Thank you for this comment. We’ve extended the introduction of the manuscript accordingly. Also, we’ve added the appropriate highlights in the discussion and conclusion part of the paper.

 

3. In the “lines 53-64” of the Introduction Section, the authors only provided different methods but failed to give the benefits and weakness of different methods.

# Thank you for this comment. We’ve extended the introduction of the manuscript accordingly.

 

4. In the Introduction, the authors should have added some other methods for assessing structural damage (i.e., PZT aggregates). This aspect can be better emphasized in the manuscript, e.g. by considering following literature

https://doi.org/10.1016/j.conbuildmat.2022.129979

# Thank you for this comment. We’ve extended the introduction of the manuscript and discussed the method presented in https://doi.org/10.1016/j.conbuildmat.2022.129979.

 

5. In the “lines 79-81”, how do you prove that the railway bridge you sampled used prestressed wire?

# Thank you for this comment. We’ve added the reference to the report of the accredited laboratory which is responsible for the data we used.

 

6. In Figure 6, which section of the corroded wire is observed in the 3D profile using the microscope HIROX RH2200?

# Thank you for this comment. We’ve added the marking at the Fig 4 in order to precisely set the observed section.

 

7. Why are the sample numbers in Table 1 and Table 3 inconsistent?

# Thank you for this comment. We’ve added the comment about this inconsistency, which explain that the number of specimens for dimension control and tensile testing does not match, because one of the samples is used for chemical testing and microscopy analysis.

 

8. The tensile test results do not intuitively give the conclusion stated in "lines 135-136". Further explanation is requested.

# Thank you for this valuable comment. We’ve added the additional explanation how the analysis given in this part of the paper is obtained, based on experimentally obtained results of dimensional analysis (table 2) and tensile testing (table 3) and their comparison to the referent values.

 

9. In the Theory of Critical Distances, why is half of the critical distance, namely L/2, adopted instead of Ldirectly (As shown in “Lines 231-232”)?

# Thank you for this valuable comment. We’ve added additional explanation in the introduction part of the manuscript regarding TCD method and Point TCD method we used in the developed methodology:

“The main idea of the TCD is the definition of an effective stress, which is equal to the stresses at a point located at a critical distance from the stress concentrator (so called Point TCD Method). In this definition, TCD uses a half of the characteristic material length parameter, so-called critical distance L/2 which is equal to the critical length of the crack (crack with the capacity to grow further to failure), to predict both brittle fracture and fatigue fracture [defined by Taylor].”

10. In this paper, Figure 15 is one of the most important figures, but the authors do not discuss it in detail.

# Thank you for your valuable comment. We’ve reorganized the part of the text in the manuscript and extended the discussion of the procedure shown in this figure. Also, due to reorganization of the figures in the manuscript under the requirement of a reviewer, Fig 15 is re-numbered in Fig 13.

Reviewer 3 Report

The authors have studied the life assessment of corroded wire for prestressing by evaluating remaining load capacity using theory of critical distances. The authors also did spatial 3D characterization of corroded surface and determined the mechanical properties using finite element analysis (FEA) modeling of wire with corrosion pits.

The results are interesting. However, some issues still exist that need to address before publication.

 

1.      The introduction section should be improved. More references should be added to indicate the originality of this work.

2.      Please discuss the important references separately, for example, 2-4, 10-11, 12-13, etc.

3.      The font size should be increased in Fig. 1 to make it more clear for the reader.

4.      Please add scale bars on figures 2 and 3.

5.      The fonts and labels are not visible in Fig. 6. Please improve the clarity of this figure.

6.      Please discuss the highlight of figure 8.

7.      Figure 11-14 can be clubbed together. The authors should think about it.

8.      The conclusions are too broad. Please include only important conclusions in this section, preferably in bulleted format.

 

9.      Additionally, English should be polished.

 

Author Response

The authors have studied the life assessment of corroded wire for prestressing by evaluating remaining load capacity using theory of critical distances. The authors also did spatial 3D characterization of corroded surface and determined the mechanical properties using finite element analysis (FEA) modeling of wire with corrosion pits.

The results are interesting. However, some issues still exist that need to address before publication.

# Thank you for your kind comment, as well as for very valuable suggestions that help us to improve the manuscript.

 

1. The introduction section should be improved. More references should be added to indicate the originality of this work.

# Thank you for your valuable comment. We’ve extended the introduction of the manuscript accordingly.

 

2. Please discuss the important references separately, for example, 2-4, 10-11, 12-13, etc.

# Thank you for your valuable comment. We’ve given additional discussions.

 

3. The font size should be increased in Fig. 1 to make it more clear for the reader.

# We’ve re-drawn Fig.1 to provide increased font size and make it more clear for the reader.

 

4. Please add scale bars on figures 2 and 3.

# Thank you for this remark. Since the Fig 2 and 3 are the original photos of the object in exploitation, we couldn’t add the scale bars on these photos, but we’ve added the data that the diameter of ducts contain corroded wires was 40mm in these photos, which dimensionally determines all presented details.

 

5. The fonts and labels are not visible in Fig. 6. Please improve the clarity of this figure.

# We’ve increased the Fig.6 in order to provide better clarity of the details, numbers and text given at this figure. This picture is an original output of the digitalized microscope HIROX RH2200, therefore, we can’t make any changes at the picture which will be change the originality of this output.

 

6. Please discuss the highlight of figure 8.

# Thank you for this valuable comment. We’ve added the explanation of the importance of the set-up for testing, shown at Fig 8.

 

7. Figure 11-14 can be clubbed together. The authors should think about it.

# Thank you for this very valuable comment for improvement of results’ discussion. We re-organized the figures 12-14 at figure 12a-12c.

 

8. The conclusions are too broad. Please include only important conclusions in this section, preferably in bulleted format.

# Thank you for your valuable comment. We’ve revised the conclusion part of the manuscript in accordance with this comment.

 

9. Additionally, English should be polished.

# Thank you for this remark. We’ve polished English throughout the manuscript.

Reviewer 4 Report

The objective of this paper  is to describe the methodology for life assessment of corroded prestressing wire, sampled from pre-stressed concrete element after few decades of exploitation. The aim of the presented research was to determine the real properties of corroded wire in terms of evaluation of remaining load capacity using Theory of Critical Distances (TCD). Overall the paper is very interesting and meaningful for the industry. The paper is very well written and can be published in this jornal after minor revision.

 

Figure 2 and 3, there is no scale bar, please add the scale bar.

 

Has the author analyzed the corrosion product as shown in Figure 5? The composition of the corrosion product is very important for the readers.

Figure 7 is very interesting, have the author done EDS mapping? Thie is very imortant for the readers.

Author Response

The objective of this paper is to describe the methodology for life assessment of corroded prestressing wire, sampled from pre-stressed concrete element after few decades of exploitation. The aim of the presented research was to determine the real properties of corroded wire in terms of evaluation of remaining load capacity using Theory of Critical Distances (TCD). Overall the paper is very interesting and meaningful for the industry. The paper is very well written and can be published in this journal after minor revision.

# Thank you for your kind comment, as well as for very valuable suggestions that help us to improve the manuscript

 

- Figure 2 and 3, there is no scale bar, please add the scale bar.

# Thank you for this remark. Since the Fig 2 and 3 are the original photos of the object in exploitation, we couldn’t add the scale bars on these photos, but we’ve added the data that the diameter of ducts contain corroded wires was 40mm in these photos, which dimensionally determines all  of the presented details.

 

- Has the author analyzed the corrosion product as shown in Figure 5? The composition of the corrosion product is very important for the readers.

# Thank you for this valuable comment. We’ve added the explanation that an extensive chemical testing is not performed, in accordance with the main aim of the presented research and developed methodology, which is assessment of residual load carrying capacity of prestressing wires.

 

- Figure 7 is very interesting, have the author done EDS mapping? This is very important for the readers.

# Thank you for this valuable comment. We’ve added the explanation that an extensive chemical testing, for example with Energy Dispersive Scanning (EDS), is not performed, in accordance with the main aim of the presented research and developed methodology, which is assessment of residual load carrying capacity of prestressing wires.

Round 2

Reviewer 2 Report

The author has revised most of the comments, but the reply to some comments is unsatisfactory. The author needs to reply to the reviewer's comments in detail in the comments, instead of asking the reviewers to find the original manuscript. A major revision is recommended.

1.      Line 19-21, In the abstract, the author should add the specific conclusions obtained by the proposed method; what problem does it solve? Give a specific explanation.

2.      In the lines25-27, General building materials are indeed challenging to meet the requirements of special projects such as bridges, so researchers have done a lot of research work, such as adding fibers and nanomaterials to strengthen and toughen, as developing ultra-high-performance concrete for bridges and offshore wind turbine platforms. Nanomaterials which is often used in reinforced concrete to improve its performance of concrete. It is recommended that the author add reference 2（https://doi.org/10.1016/j.jobe.2022.104880）after reference 1 to make the background part more logical.

3.      The Fig should be consistent in size and format across the full manuscript.

 

4.      In conclusion, the authors should look forward to the application prospects of the proposed method.

Author Response

Reviewer 2

The author has revised most of the comments, but the reply to some comments is unsatisfactory. The author needs to reply to the reviewer's comments in detail in the comments, instead of asking the reviewers to find the original manuscript. A major revision is recommended.

# Thank you for your kind comment, as well as for very valuable suggestions that help us to additionally improve the manuscript.

1. Line 19-21, In the abstract, the author should add the specific conclusions obtained by the proposed method; what problem does it solve? Give a specific explanation.

# Thank you very much for this valuable recommendation. We’ve added the required specific conclusion in the abstract, as follows:

“The results and conclusions indicate that the developed methodology, based on the interdisciplinary approach and implementation of state-of-the-art methods, has a high applicability potential for both static and fatigue fracture prediction in the case of prestressing wires. The proposed method has a huge potential for simple and fast prediction of life assessment of engineering structures, particularly for damaged elements with arbitrary geometry features.”

2. In the lines25-27, General building materials are indeed challenging to meet the requirements of special projects such as bridges, so researchers have done a lot of research work, such as adding fibers and nanomaterials to strengthen and toughen, as developing ultra-high-performance concrete for bridges and offshore wind turbine platforms. Nanomaterials which is often used in reinforced concrete to improve its performance of concrete. It is recommended that the author add reference 2（https://doi.org/10.1016/j.jobe.2022.104880）after reference 1 to make the background part more logical.

# Thank you for this remark. We’ve extended the introduction of the manuscript accordingly. We added following sentence:

“General building materials are indeed challenging to meet the requirements of special projects such as bridges, so researchers have done a lot of research work, such as adding fibers and nanomaterials to strengthen and toughen, as developing ultra-high-performance concrete for bridges and offshore wind turbine platforms. Nanomaterials is often used in reinforced concrete to improve its performance of concrete [2].”

As well as, we added the suggested reference https://doi.org/10.1016/j.jobe.2022.104880:

2. Cui, K.; Chang, J. Hydration, reinforcing mechanism, and macro performance of multi-layer graphene-modified cement composites. Build. Eng.2022, 57, 104880. DOI: 10.1016/j.jobe.2022.104880
3. The Fig should be consistent in size and format across the full manuscript.

# Thank you very much for very valuable suggestion. We’ve re-drawing the Fig 1 and also made all figures throughout the manuscript consistent in size and format.

4. In conclusion, the authors should look forward to the application prospects of the proposed method.

# Thank you very much for this valuable recommendation. We’ve extended the last part of the conclusions, as follows:

“Finally, it can be concluded that the main advantage and contribution of presented new methodology is a possibility to quantify the conditions of occurrence of both static and fatigue fracture. The developed methodology has a high potential for implementation on different geometric stress concentrators, separately or grouped, in order to give prompt and accurate prediction of life assessment of engineering structures, particularly for damaged elements with arbitrary geometry features. The very specific and state-of-the-art perspectives of the proposed method could be expected in the field of artificial intelligence as a part of health monitoring systems.”

Round 3

Reviewer 2 Report

The author has revised all the comments made by the reviewers, the quality of the manuscript has been dramatically improved, and it is recommended to accept.