Study on the Attack of Concrete by External Sulfate under Electric Fields

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors presented the results of interesting scientific research of significant engineering value. However, the reviewer did not find a solid presentation of the practical application of the results. It would be useful to provide examples of structures operating in an electric field and exposed to sulfate corrosion.

The studies showed a significant increase in the corrosion rate in the electric field compared to other environments and a clear increase in this phenomenon with the increase in the w/c ratio.

Due to the small differences in values ​​due to the random nature of concrete, drawing quantitative conclusions is somewhat unjustified. The mere recognition of the influence of environmental parameters on the rate of development of sulphate corrosion is already a certain scientific conclusion.

The work contains a number lacks and of editorial errors that should be corrected, for example:

1) Please specify the type of coarse aggregate used. This may be helpful in interpreting the results for other researchers. Term "crushed stone" is too pour. The type of aggregate may affect sulphate corrosion.

2) Table 2: Please explain so high value of flexural strength of Portal Cement (8.8 MPa after 3 days, 53.0 Mpa after 28 days)

3) Figure 4 and 5: low quality

4) Section: 3.4 Evaluation Criteria

The first two sentences mean the same, they just use different words.

Terms: M1, M2 and m1, m2 are used interchangeably. Either M1, M2 or m1, m2.

5) Discription of Figure 29, 30, 31: What does "Shimizu group" mean ?

6) Discription of Figure 33, 35, 37: Does "test group" means the samples in an electric field?

7) Please mark the intact lamellar Ca(OH)2 crystals and ettringite crystals on Figure 32-34.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The topic of the article has been widely researched in the scientific community. The manuscript has a number of shortcomings that need improvement:

In general revise the wording, which should be correct and clear.

Incorrections in English language.

Title: delete "on the rules".

Abstract:

The wording could be improved (repetition of words, incorrect sentence structure, unclear wording).

What is meant by conventional erosion? under what conditions?

Introduction:

References 6-7. References from 2006 and 1998 are not recent enough to ensure that "the research demand for sulfate resistance of concrete is increasing".

Reference 21 has no sense where it is placed.

The introduction should be expanded with the most relevant results and conclusions of the most recent studies in this field. The references used are mostly more than 5 years old.

Experimental programme:

Tables: Modify the size of the cells in the tables so that the titles are not cut off.

Add manufacturers' names for all materials and origin. Also the origin of the data (are they own tests or supplied by the manufacturer?, in the second case add references).

Indicate the composition of coarse aggregate. 

Add granulometric curve of the aggregates.

Explain the reason for the specifications used as well as the water/cement ratio. What criteria have been followed? Explain

Specify the composition of the solution.

Specify the dimensions of the moulds and plates.

Lin. 105. It is not clear whether how many test specimens were made for each dosage.

Indicate the standards used for the preparation of the specimens and the tests carried out.

Describe what is meant by "partial immersion", "full immersion".

Throughout the article, check that the superscripts in the units appear as such.

Table 5 . Specify the units of the values obtained.

Lin 118-121. Is the sentence repeated?

Lin. 124 remove and replace by: where, k is the mass... (repeat for all other equations).

Lin 25. K should appear as in the equation "k". Same for the rest of the equations.

Add more details about the methodology of the experiments (voltage and current used, times).

Results:

Figure 6-7. Immersion times should appear in the methodology.

Lin 163-167. These are data that should appear in the methodology.

Table 6. units in the table header in brackets.

Further explanation of the results obtained is needed.

Section 4.3 should be renamed, as all of section 4 refers to experimental results.

Table 9. to which conditions it refers? There are no results for specimens at 14 days semi-waked as in 28 days.

The graphs and tables of the results should be included in the same section for better understanding.

Lin 200. The trend is not clearly represented. 

The analysis and interpretation of all results should be supported by consistent bibliographic references.

Figure 29 what does Shimizu group, solution group and test group refer to? is not explained in the methodology.

From figure 29 to 37, group the images and reduce the number of figures.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

SUMMARY

The article submitted for review is relevant to modern science and engineering practice. The article investigates the patterns of concrete resistance to sulfate exposure in an electric field. The authors have developed a new test method using the principle of an electric field. To accelerate the erosion of sulfate in concrete under the influence of an electric field, the resistance of concrete to sulfate exposure is checked. After conducting a number of physical and laboratory experiments, the authors obtained important results that showed new dependences of concrete strength in a sulfate environment on various factors. The authors also studied the microscopic morphology of the samples. Different variations of the water-cement ratio and other experimental conditions were studied. 

The article provides new theoretical fundamental information that can form the basis of new engineering developments. The reviewer believes that the research has been carried out at a high level and contains a number of important results. The article has scientific novelty and applied significance.

However, there are drawbacks in the article. They need to be eliminated. The comments are given below.

 

COMMENTS

1. The authors should more clearly justify the correspondence of the title of the article to the thematic journal “Coatings”.

2. The authors need to justify in more detail in the abstracts and in the text of the article exactly how their development will be useful for coatings. It should be noted that concrete is used in various engineering places, and often the issues of surface and surface permeability of concrete are of great relevance.

3. The abstract does not contain a statement of the scientific problem. Authors should

At the beginning of the story, what scientific deficit exists in international research on the resistance of concrete to sulphate sunlight in an electric field.

4. Also in the abstract it should be said what engineering problem is facing various scientists. The problems of concrete coatings should also be mentioned here.

5. The abstract does not contain quantitative expressions of the research results. The authors report an increase in tensile strength in sulfate-exposed environments at 14 days of age and 28 days of age, but do not report the quantitative expression of these changes. Specific percentages must be added to the annotation.

6. Looks abstract and unfinished. It is necessary to formulate a general scientific result that shows the development of the science of concrete in various aggressive conditions.

7. The literature review carried out in the Introduction section is insufficient for research of this level. 24 literary works were examined and described in detail. Many of them are simply listed. For example, line 32 lists 6 sources of literature at once. The authors need to describe this state of the issue in more detail, reveal each literary work mentioned in more detail, and also bring the total number of analyzed sources to 35-40. Then the literature review will be more complete. There are many interesting questions associated with research into the effects of electric current on concrete. For example, these electrophysical methods regulate the formation of structures and cellular concrete, as well as the activation of reinforced concrete structures by electric fields or the effect of electric current on concrete pavements. It is necessary to carry out several classifications of research and additionally be sure to emphasize the importance of the issues under consideration for scientific research on coatings.

8. At the end of the introduction section, more clear formulations of scientific problems, goals and objectives of the study should be given.

9. The authors conducted large-scale experiments, but described the materials and research methods very poorly. For example, section 2 consists mostly of tables only. The authors should disclose the methodology in more detail.

10. It is proposed that sections 2 and 3 be titled “Materials and Methods” and be made more detailed. You need to add analytical text between tables and figures. Now these sections look like a simple engineering protocol. It is proposed to supplement the combined points 2 and 3 of the experimental research program in the form of block diagrams. This will help the reader better navigate the article.

11. The “Results” section begins with photographs. This is not entirely correct. The authors need to share more careful analysis and describe the results.

12. There are questions about Figures 9-28. All these pictures show 2 or 3 points. The connection of these points is made according to the lines. It is not correct. Bar graphs should be presented here.

13. The discussion of the results obtained in section 5 should be more detailed. A more thorough comparison of the results with those of other authors is necessary.

14. The microscopic analysis in Section 6 requires a more detailed explanation of the resulting images.

15. Use the current paragraphs 5 and 6 under the general title “Discussion”. This will help identify scientific and practical innovation.

16. The list of references, as already mentioned, should be increased by 10-15 points. More analysis should be done on studies over the last 5 years.

 

Overall, the article is of great interest and contains a lot of new scientific data and engineering results. However, the authors need to seriously revise their article by making extensive changes. The general conclusion is “Major Revisions”. After correcting the comments, the reviewer would like to take another look at the article to ensure that it is more suitable for publication in Coatings.

Comments on the Quality of English Language

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

The peer-reviewed article focuses on the investigation of the resistance of concrete against sulphate attack, especially under the influence of an electric field. Note that the electric field has a significant impact on the rate and extent of corrosion. Concrete corrosion is a chemical process in which sulphates react with the hydration products of cement to form secondary minerals such as ettringite and gypsum, which cause volumetric changes and cracking of the concrete. The electric field affects the transport properties of ions in concrete, and thus the rate of chemical reactions and their distribution. In short, it can be said that corrosion in concrete can take place in several ways, e.g. in the form of a reaction with cement components, or in the form of so-called exposure to sulphate salts in an environment where water containing sulphate ions penetrates the concrete, where it reacts with calcium hydroxide and other hydration products.

The electric field affects these processes by the transport of ions in concrete due to electro migration or electro osmosis. Electro migration is the movement of ions under the influence of an electric field. Positive ions (cations) move towards the negative pole and negative ions (anions) towards the positive pole. Electro osmosis is the process of movement of liquid through the porous structure of concrete under the influence of an electric field, which can affect the transport of dissolved substances.

It is clear from the above that the article is oriented towards a very important and current issue. This is because concrete is one of the most used building materials due to its high strength and durability. However, concrete is susceptible to chemical attack, especially to so-called sulphate corrosion, which can significantly reduce its service life. This can be very significantly influenced by the action of the electric field.

The reviewed article describes a new test method proposed by the authors using the principle of electric field action leading to the acceleration of sulphate erosion into concrete to test the resistance of concrete to sulphate attack, etc. The article also deals with testing different water-cement ratios, different pulse frequencies, different ages and different the soaking environment of the samples due to the influence of the electric field and the sulphate resistance of concrete.

The article is quite long, it has 26 pages. The article has a proven structure. The title of the article and the abstract are well-crafted and engaging. The article consists of seven parts. These are well balanced. The tables and graphs used are processed to a high standard with good explanatory power. These very well enable the reader to navigate the presented problem. The English used is also at an advanced level. The contribution is related to a large number of citations, which indicates a very well-conducted research, and therefore also a very good orientation in the presented issue. The used procedure for processing the issue in question is more or less classic. Realized works are in accordance with the trends in the given issue. The testing procedures used were selected and applied correctly. All experiments are well described in the paper. This fact applies both to the description of the objectives of the tests, the description of the methods used, samples, ratios in sample mixtures, etc. The obtained graphs and other results are sufficiently commented. The obtained results follow on from previous works, predictions resulting from theoretical works and extend them. However, it seems to me that the conclusion could be more detailed.

It is necessary to appreciate the quality of the equipment of the author's collective workplace and thus also the use of modern methods of monitoring selected parameters of mixtures. In my opinion, the presented conclusions are interesting, the obtained results enrich the presented area and can be interesting both for experts in the given field and for the technical public. Although the reviewed article is of high quality, I recommend the following additions to the authors:

·       What other types of tests will be appropriate to implement in the future? For example, an outline of further additional measurement and analysis of the used samples for the purpose of a more detailed study of the described samples in different operational and climatic conditions.

·       Will it be possible to include the knowledge gained in simulation models? Or in which ones?

·       Where will further research work of the authors of the article go in the given area?

·       How will the obtained outputs be used in construction practice and what will be the economic benefit from them?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have responded to the comments made satisfactorily and the manuscript has been completed and improved, therefore I recommend its publication.

Author Response

Comments 1: The authors have responded to the comments made satisfactorily and the manuscript has been completed and improved, therefore I recommend its publication.

Response 1: Thank you very much for carefully reviewing my manuscript and providing valuable suggestions. I'm happy to hear that you suggested publishing this manuscript. Your affirmation and support are of great significance to me. 

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have thoroughly revised the article and it has become much better. The reviewer has no more comments and the article in this form can be accepted for publication in the Coatings journal

Author Response

Comments 1: The authors have thoroughly revised the article and it has become much better. The reviewer has no more comments and the article in this form can be accepted for publication in the Coatings journal.

Response 1: Thank you very much for carefully reviewing my manuscript and providing valuable suggestions. I'm happy to hear that you suggested publishing this manuscript. Your affirmation and support are of great significance to me.