Mechanical Properties and Microstructure of Rubber Concrete under Coupling Action of Sulfate Attack and Dry–Wet Cycle
Round 1
Reviewer 1 Report (Previous Reviewer 2)
It is understood that the authors worked adequately in order to meet the reviewers' considerations and questions. Thus, in terms of content, data and discussions, the work is ready to be published
However, a detailed review of some figures is recommended, including standardization in the style of presenting data in the graphs.
Figure 2 - just mention Km(%) on the ordinate axis. In the caption mention relative mass value Km(%)
Figure 3 - mention only Edr (%) on the ordinate axis. In the caption: same observation as in the previous figure
Figure 4.1- What did the authors intend to show? Further details are suggested on the main test devices.
Figure 5 - mention only Kf on the ordinate axis.
Figure 6 - mention only P(%) on the ordinate axis.
Author Response
Response to Reviewer 1 Comments
It is understood that the authors worked adequately in order to meet the reviewers' considerations and questions. Thus, in terms of content, data and discussions, the work is ready to be published.
However, a detailed review of some figures is recommended, including standardization in the style of presenting data in the graphs.
Point 1:Figure 2 - just mention Km(%) on the ordinate axis. In the caption mention relative mass value Km(%)
Response 1:Thanks for the teacher 's comments, have been modified in the text. See line 212-215 in Figure 2.
Point 2:Figure 3 - mention only Edr (%) on the ordinate axis. In the caption: same observation as in the previous figure
Response 2:Thanks for the teacher 's comments, have been modified in the text. See figure III, line 285-288.
Point 3:Figure 4.1- What did the authors intend to show? Further details are suggested on the main test devices.
Response 3:Thanks to the teacher 's suggestion, Figure 4.1 is the RDL electronic creep relaxation tester. Due to the lack of pictures of the instrument and equipment in the paper, we want to show the main equipment used for uniaxial failure.
Point 4:Figure 5 - mention only Kf on the ordinate axis.
Response 4:Thanks for the teacher 's comments, which have been revised in the article. See Figure 5, lines 317-320.
Point 5:Figure 6 - mention only P(%) on the ordinate axis.
Response 5:Thanks for the teacher 's comments, which have been revised in the article. See Figure 6, lines 374-377.
Author Response File: 
Author Response.pdf
Reviewer 2 Report (Previous Reviewer 3)
The authors were corrected many parts of the manuscript according to reviewers suggestions. However the questions in the microstructural analysis has not been explained. Maybe authors don't have additional material to have an edx. However they should explain how they know the components by sight.
Minor check in needed.
Author Response
Response to Reviewer 2 Comments
Comments and Suggestions for Authors
Point 1:The authors were corrected many parts of the manuscript according to reviewers suggestions. However the questions in the microstructural analysis has not been explained. Maybe authors don't have additional material to have an edx. However they should explain how they know the components by sight.
Response 1:Thanks to the teacher 's correction, has been added in the text. See lines 381-386. In the SEM microscopic image of the concrete specimen, ettringite is presented in the form of clusters, and gypsum is presented in the form of plates and columns to fill the gap cracks of the specimen.
Comments on the Quality of English Language
Point 1:Minor check in needed.
Response 1:Thanks to the teacher 's reminders and suggestions, the quality of English language has been revised and improved.
Author Response File: Author Response.pdf
Reviewer 3 Report (New Reviewer)
The paper investigates the performance of rubber concrete under dry-wet cycles in sulfate environment. The application of three different particle sizes of rubber is evaluated by means of morphology and mass loss analysis, relative dynamic elastic modulus as well as compressive strength reduction. The topic of the study is interesting and important from the environmental perspective, since it involves the potential recycling of tire rubber. Nevertheless, my questions and major remarks for the paper can be found below:
1. Introduction – the abbreviations should be explained when they appear for the first time in the text (for example SEM, CT in line 60).
2. Introduction – more details and numbers should be added to the discussion of the studies found in the literature. The authors stated that, for example, “resistance was improved”, “quality and strength were increased” – please give us more details, what was exactly the range of the improvement, etc.?
3. Raw materials – since the rubber is an important and fundamental material within this study, more details and characteristics of it should be introduced into the paper – type, composition, basic parameters etc.
4. Results, visual control – since the crucial part of the paper is the comparison of the performance of rubber concrete and the reference concrete, the photos of standard concrete should be included in Figure 1. Could you also explain what do you mean by “the passivation of sample’s ends” in line 144?
5. Results, general comment – could you please specify how many samples for each concrete type were measured in each test? This information is missing in the text and the error bars are missing in Figures 2, 3, 5 and 6.
6. Results, SEM – please complete the captions of Figures 6 and 7. The difference between images a, b, c etc. should be described in the caption.
7. Results, general comment – in my opinion, the results and discussion part of the paper should be restructured. The authors discuss the results of each experiment separately and, as a consequence, there are many repetitions in the text. After each experiment, the authors give similar explanations and descriptions of the phenomena related to the sulfate corrosion of concrete, for example we can find three times within the text similar sentences about the penetration of sulfate ions into concrete: in lines 193, 235, 279. I would suggest to, first, present the results of the experiments and then discuss them together and present the common explanations and conclusions.
8. Results, general comment – could you please comment on the potential influence of the rubber on the obtained results? To be more precise, do you know if there is any effect of the applied chemicals, i.e., sodium chloride, concrete environment or the drying temperatures on the stability and properties of the rubber itself?
9. Results, general comment – could you please provide some comparison of the obtained results with results of similar research available in the literature?
In my opinion, some language corrections are required, i.e., some expressions or sentences are not grammatically correct, in some places words are missing. Examples: lines 108-110, 117-118, 171, 270.
Author Response
Response to Reviewer 3 Comments
Comments and Suggestions for Authors
The paper investigates the performance of rubber concrete under dry-wet cycles in sulfate environment. The application of three different particle sizes of rubber is evaluated by means of morphology and mass loss analysis, relative dynamic elastic modulus as well as compressive strength reduction. The topic of the study is interesting and important from the environmental perspective, since it involves the potential recycling of tire rubber. Nevertheless, my questions and major remarks for the paper can be found below:
Point 1:Introduction – the abbreviations should be explained when they appear for the first time in the text (for example SEM, CT in line 60).
Response 1:Thanks to the teacher 's guidance, has been modified in the text. See lines 65-66.
Point 2:Introduction – more details and numbers should be added to the discussion of the studies found in the literature. The authors stated that, for example, “resistance was improved”, “quality and strength were increased” – please give us more details, what was exactly the range of the improvement, etc.?
Response 2:Thanks to the teacher 's guidance, the corresponding modifications have been made in the text, and details and digital descriptions have been added to the cited literature. For example, Reference 11, see lines 32-35 in the text. Reference 24, see lines 55-61. Reference 27, see lines 73-77. There is a lack of many details in the text before, and it has been improved. More principles and the exact scope of improvement have been supplemented. For example, Literature 26 gives the principle of mass and strength changes, as shown in lines 65-73.
Point 3:Raw materials – since the rubber is an important and fundamental material within this study, more details and characteristics of it should be introduced into the paper – type, composition, basic parameters etc.
Response 3:Thank you very much for the advice given by the expert teacher. The chemical composition and parameter index of rubber particles have been added to the text, as shown in table 2 and table 3. Line 106-107.
Point 4:Results, visual control – since the crucial part of the paper is the comparison of the performance of rubber concrete and the reference concrete, the photos of standard concrete should be included in Figure 1. Could you also explain what do you mean by “the passivation of sample’s ends” in line 144?
Response 4:Thanks to the teacher 's suggestion, the apparent analysis of this paper is mainly to analyze the apparent phenomenon of different rubber particle sizes. Only the apparent photos of rubber concrete are taken, thus ignoring the apparent photos of reference concrete. In the future test, we will pay attention to the recurrence of such problems. In this paper, the ' passivation of the end of the sample ' means that the specimen is subjected to 120 dry-wet cycles in the sulfate solution. Due to the erosion of sulfate, fine cracks will occur at the end, fine aggregate will peel off, and coarse aggregate will be exposed. At the same time, the specimen is subjected to physical and chemical crystallization, and the expansion pressure from physical crystallization will cause damage such as porosity and spalling at the end of the concrete. Chemical crystallization, that is, SO42- enters the concrete, and hydration reaction occurs to generate expansive products gypsum and ettringite, thereby generating internal stress inside the specimen. Once the tensile strength of concrete is lower than the sum of the expansion pressure of the erosion products, cracks will appear and further deteriorate, and the end passivation will become more obvious.
Point 5:Results, general comment – could you please specify how many samples for each concrete type were measured in each test? This information is missing in the text and the error bars are missing in Figures 2, 3, 5 and 6.
Response 5:Thanks to the advice given by the expert teacher, the number of samples has been supplemented in the article. The concrete specimens were divided into four groups : NC, RC-0.85, RC-1-3 and RC-3-6. The uniaxial compressive strength and fatigue failure strength of each group of specimens were tested after 0,30,60,90,120 dry-wet cycles. There were 30 specimens in each group, a total of 120. See lines 121-124. In order to better reflect the damage caused by dry-wet cycle in sulfate solution, this paper adopts the form of ratio instead of error bar. In the future thesis writing, will be more targeted to strengthen the use of error bars, thanks to the teacher to give advice.
Point 6:Results, SEM – please complete the captions of Figures 6 and 7. The difference between images a, b, c etc. should be described in the caption.
Response 6:Thanks to the teacher 's correction, the title has been added in the text.
Point 7:Results, general comment – in my opinion, the results and discussion part of the paper should be restructured. The authors discuss the results of each experiment separately and, as a consequence, there are many repetitions in the text. After each experiment, the authors give similar explanations and descriptions of the phenomena related to the sulfate corrosion of concrete, for example we can find three times within the text similar sentences about the penetration of sulfate ions into concrete: in lines 193, 235, 279. I would suggest to, first, present the results of the experiments and then discuss them together and present the common explanations and conclusions.
Response 7:Thanks to the teacher 's suggestion, the results of each part of the paper are put together with the discussion part because they want to better explain the principle of the results. The similar explanation and description are explained from the finer aspects of each aspect. The relevant details have been adjusted in the text.
Point 8:Results, general comment – could you please comment on the potential influence of the rubber on the obtained results? To be more precise, do you know if there is any effect of the applied chemicals, i.e., sodium chloride, concrete environment or the drying temperatures on the stability and properties of the rubber itself?
Response 8:Thanks for the teacher 's question. Sodium sulfate solution has little effect on rubber particles, but rubber particles are alternately subjected to high temperature and low temperature, which is easy to cause rubber aging. This irreversible chemical reaction will cause the particles to become soft or hardened. Therefore, the chemicals used have a certain influence on the rubber particles. In the subsequent experiments, the rubber particles can be modified by sodium hydroxide and synthetic resin to improve the stability of the rubber particles.
Point 9:Results, general comment – could you please provide some comparison of the obtained results with results of similar research available in the literature?
Response 9:Thanks for the teacher's question. For example, in reference 26, Wei Tian et al.revealed the damage evolution of concrete by SEM and CT. In the early stage of sulfate attack, the pore structure of concrete was destroyed, and ettringite and gypsum were formed, and its quality and strength increased. As the deterioration progresses, the expansion force of the product and the salt crystallization pressure of the sulfate crystal act on the inner wall of the concrete and accelerate the deterioration. The quality and strength of concrete decreased sharply, indicating that the quality and strength of concrete increased first and then decreased with the increase of the number of dry and wet cycles of sulfate attack. It is consistent with the experimental damage results in this paper.
Comments on the Quality of English Language
Point 1:In my opinion, some language corrections are required, i.e., some expressions or sentences are not grammatically correct, in some places words are missing. Examples: lines 108-110, 117-118, 171, 270.
Response 1:Thanks to the teacher 's reminders and suggestions, the quality of English language has been revised and improved.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report (Previous Reviewer 3)
The manuscript can be accepted as is.
Reviewer 3 Report (New Reviewer)
The authors have taken into consideration and addressed most of my comments: crucial details have been added into the text, the structure of the paper has been modified and the level of English language has been improved sufficiently.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
Introduction is not broad enough on the subject. Please tell us about different studies on the subject and their results.
Please share photos of the experimental setup and damage after the experiment.
Did you use equal amounts of different rubber diameters?
Why was the standard deviation not mentioned in repeated tests?
The calculation section of the material elasticity module does not provide clear enough calculations.
Author Response
Dear reviewer:
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
In this paper, dry-wet cycle test and cyclic loading-unloading test were carried out on rubber concrete with different rubber particle sizes in sulfate environment. The damage and deterioration degree of RC after different dry-wet cycle stages and the fatigue performance of RC after cyclic loading-unloading were measured and analyzed. The internal damage of concrete was reflected by non-destructive ultrasonic test and scanning electron microscopy, and the microscopic mechanism was analyzed. The theme is well contextualized, it has environmental significance and the methodology is coherent and very well explained and detailed.
It is recommended to replicate the dimensions of the specimens (ln87) in the caption of Figure 1.
It is observed that the values of Km and relative dynamic elastic modulus increase from 0 to 60 cycles and then decrease in the other 60 cycles. The interrelations with physical aspects of the materials are very well placed and discussed. The same context can be attributed to the presentation and discussion of mechanical strength data and its degradation. Microstructural analysis adequately corroborates the discussion of results.
Conclusions are well highlighted, but could be more objective.
Author Response
Dear reviewer:
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The authors presented a study on using rubber in different particles sizes. The samples subjected to sulfate effect by dry-wet cycles and also samples subjected to cyclic loading. The manuscript has experimental findings, however the science behind these findings are completely missing. Also, there is no discussion with literature. There are some suggestions and questions below;
- The properties of cement (oxide analyse, LOI, specific gravity) should be given. Specific gravity of fly ash should be given.
- What is the origin of HRWR
- Please give the specific gravity of rubber particles.
- Lines 83 , 84, The sentence is not clear. The usage amount is not understandable.
- Table 2, sand amount is changing for mixtures, however, why the rubber amount is constant. It say %10 by weight for the replacement amount. There looks a mistake.
- Line 95, Now it says %10 by volume? Which one is right?
- Line 103 - 106. How did you determine the drying quality by using ultrasonic method? The values can change after the effect of sulfate exposure due to detrimental effects.
- Lines 125 - 137, What do authors think about the errosion change with the particles size? What is the effect of rubber and rubber particles size?
- Quality loss analysis, please discuss with the literature, is there any examples of this situation? How do you know that ettringite and gypsum formation by sulfate ions? Authors didn't give any literature.
- The formula of Km doesn't give % value of relative mass. You need to multiply it by 100.
- Figure 2, y axis, please give the value as %, because it was stated that % is determined by formula.
- Lines 155 - 177. It is stated that the rubber particles reduce the permeability? How did author know that? There is no literature example, there is no permeability test. These finding should be discussed.
- Line 191, it shoud better to use "pulse" instead of "sound".
- Please give reference for Edr formula.
- Line 189, How did authors know that large number of SO4 ions enter to the system?
- Lines, 200 - 213, Please discuss these findings with literature. Why? What is the science behing these findings?
- Section 3.4 Please give the original compressive strength values and the values after sulfate exposure.
- Section 3.4. Please discuss the results with literature and please give the science behind these results.
- Figure 4, y axis, write also as Kf.
- Line 249, it is stated that the compactness of RC samples is better. How did authors know that?
- Line 272 - 290, Why did fatigue damage affected in this way? What is the science behind these results? Also, in order to understand the elastic properties, elastic modulus should be measured. Besides, the results should be discussed with the literature.
- Authors indicated some formations like ettringite and gypsum on the SEM images. However, there is no evidince that these formations are ettringite and gypsum. EDX is needed. On the other hand, these formations do not like the samples in the literature. Please discuss and show expamples of these formations from literature. For example, ettringite crystal mostly look like needle-like crystals. However there is no such thing in these images. Also, in the SEM images rubber particles should be shown. This can help to understand the ITZ formation between rubber particles and cement matrix.
Author Response
Dear reviewer:
Please see the attachment.
Author Response File: Author Response.pdf
