Influence of Basalt Fiber on Mechanical Properties and Microstructure of Rubber Concrete

Round 1

Reviewer 1 Report

This manuscript studies the effects of rubber particles and basalt fiber on the strength and micro-structure of concrete. The research results lay a theoretical foundation for the engineering application of rubber concrete, but there are still the following problems that need to be explained and supplemented.

1. In the abstract, "The pores introduced are mostly small volume confined pores, which can improve the durability characteristics of the concrete such as impermeability and frost resistance." is not reflected the durability of concrete in the article, whether there is a specific phenomenon to explain.

2. The main highlights of this article are not described in the introduction, in other words, where is the novelty of this article?

3. In this manuscript, the addition of 0.1% basalt fiber is or not the appropriate fiber content used in this experiment, what is the specific basis for selecting this fiber content, and is there any relevant research as the basis?

4. Why is the apparent phenomenon of the specimen in figure 4 so different? The surface of the concrete in figure 4 (a) is so rough, will this affect the experimental results?

5. Section 3.2 for the analysis of compressive and tensile strength, there is only one set of data for each group of different types of concrete. As the randomness of concrete test is relatively large, whether 3-5 specimens of each type of concrete have been made, please reflect it in this paper.

6. In section 3.3, " At the same time, since the introduced pores are mostly small volume confined pores, they also improve the durability characteristics of concrete such as impermeability and frost resistance accordingly." is obvious that it is not consistent with the phenomenon in figure 7, and the pore size and number in figures 7 (b) and 7 (c) are significantly larger than those in figure 7 (a). Please add to this question.

7. The conclusion describes too much and does not directly explain the problems solved and the phenomena found in this manuscript, so this part should be simplified.

Author Response

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript sustainability-1881777. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. The main corrections in the paper and the responds to the reviewer’s comments are as following:

This manuscript studies the effects of rubber particles and basalt fiber on the strength and micro-structure of concrete. The research results lay a theoretical foundation for the engineering application of rubber concrete, but there are still the following problems that need to be explained and supplemented.

1. In the abstract, "The pores introduced are mostly small volume confined pores, which can improve the durability characteristics of the concrete such as impermeability and frost resistance." is not reflected the durability of concrete in the article, whether there is a specific phenomenon to explain.

Reply: Thanks for the comment. This article mainly studies the effects of rubber particles and basalt fibers on the mechanical properties and microstructure of concrete. The change of pore structure will affect the durability of concrete, we think it is very important to study its durability, which is also one of our main work in the next step, we will show the effect of rubber particles and basalt fibers on the durability of concrete in the follow-up article. Therefore, there is no specific phenomenon explanation in the article. The relevant description in the abstract has been modified.

2. The main highlights of this article are not described in the introduction, in other words, where is the novelty of this article?

Reply: Thanks for the comment. Previous scholars mainly studied the pore structure through mercury injection method, which will damage the pore of the test block and affect the experimental results in the process of making the sample. While studying the hole structure through CT can clearly and nondestructive study the internal structure of the tested object, studying the concrete hole structure through CT is the novelty of this paper. This article also uses CT scan photos to reconstruct the distribution map of rubber particles in concrete using Avizo software. See lines 307-313.

3. In this manuscript, the addition of 0.1% basalt fiber is or not the appropriate fiber content used in this experiment, what is the specific basis for selecting this fiber content, and is there any relevant research as the basis?

Reply: Thanks for the comment. In the early stage of the experiment, we prepared basalt fiber concrete with a mass fraction of 0.1%, 0.2% and 0.3%. When the mass fraction of basalt fiber is greater than 0.1%, the compressive strength of the test block decreases and the splitting tensile strength increases. Under the condition of ensuring the matrix strength, we selected basalt fiber with a mass fraction of 0.1%, which has been modified in the original text. See lines 109-118.

4. Why is the apparent phenomenon of the specimen in figure 4 so different? The surface of the concrete in figure 4 (a) is so rough, will this affect the experimental results?

Reply: Thanks for the comment. Figure 4 (a) is the molding surface of concrete, and Figure 4 (b) (c) is the side surface of concrete. Therefore, the phenomenon is different. The picture of Figure 4 (a) has been modified. According to the code 'GB50081-2002 standard for test methods of mechanical properties of ordinary concrete, the strength of the concrete test block was tested. The side of the test block was pressed by the pressure tester, which has nothing to do with the forming surface. Therefore, the experimental results will not be affected. The original figure 4 (a) has been modified, see line 204.

5. Section 3.2 for the analysis of compressive and tensile strength, there is only one set of data for each group of different types of concrete. As the randomness of concrete test is relatively large, whether 3-5 specimens of each type of concrete have been made, please reflect it in this paper.

Reply: Thanks for the comment. Eight test blocks were formed for each proportion of concrete, of which three were used to test the compressive strength, three were used to test the splitting tensile strength, and two were used for CT scanning. The data were processed according to China Standards GB50081-2002 for test methods of mechanical properties of ordinary concrete. The data of compressive strength and splitting tensile strength are shown in table 5 and table 6.

6. In section 3.3, " At the same time, since the introduced pores are mostly small volume confined pores, they also improve the durability characteristics of concrete such as impermeability and frost resistance accordingly." is obvious that it is not consistent with the phenomenon in figure 7, and the pore size and number in figures 7 (b) and 7 (c) are significantly larger than those in figure 7 (a). Please add to this question.

Reply: Thanks for the comment. The previous picture contains a large number of large holes due to improper mixing in the concrete forming process. The original picture has been deleted, and a new basalt fiber rubber concrete test block has been retested with CT, and the image results have been analyzed. Corresponding to lines 272-292 in the text

7. The conclusion describes too much and does not directly explain the problems solved and the phenomena found in this manuscript, so this part should be simplified.

Reply: Thanks for the comment. The conclusion has been modified.

Author Response File: Author Response.pdf

Reviewer 2 Report

General Comments

1-    The literature review should be improve and include more reference.

2-      The languages still need major improvements .Improve the clarity of the manuscript. The authors should improve the spellings, grammar.

3-      The figure captions are not clear.

Technical Comments

1-What is the novelty of this article? 

2- The design of experiments should be mentioned in the article.

3-Page 6- line 201: Why  basalt fibers are haphazardly distributed within the matrix after being incorporated into concrete?

4-Page 8- line 252: Why  the hydration products cannot fill the pores? 

Author Response

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript sustainability-1881777. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. The main corrections in the paper and the responds to the reviewer’s comments are as following:

General Comments

1- The literature review should be improve and include more reference.

Reply: Thanks for the comment. The literature review has been modified, and relevant literature has been modified.

2- The languages still need major improvements. Improve the clarity of the manuscript. The authors should improve the spellings, grammar.

Reply: Thanks for the comment. The language problem has been corrected.

3- The figure captions are not clear.

 Reply: Thanks for the comment. Figure captions has been modified.

Technical Comments

• What is the novelty of this article? 

Reply: Thanks for the comment. Previous scholars mainly studied the pore structure through mercury injection method, which will damage the pore of the test block and affect the experimental results in the process of making the sample. While studying the hole structure through CT can clearly and nondestructive study the internal structure of the tested object, studying the concrete hole structure through CT is the novelty of this paper. This article also uses CT scan photos to reconstruct the distribution map of rubber particles in concrete using Avizo software. See lines 307-313.

2-The design of experiments should be mentioned in the article.

Reply: Thanks for the comment. Experimental design has been supplemented in lines109-123.

3-Page 6- line 201: Why basalt fibers are haphazardly distributed within the matrix after being incorporated into concrete?

Reply: Thanks for the comment. Because the density of basalt fiber is 2.61, which is similar to the density of stone and sand, and basalt fiber is an inorganic non-metallic material with good compatibility with cement matrix, basalt fiber will be randomly distributed in concrete.

4-Page 8- line 252: Why the hydration products cannot fill the pores? 

Reply: Thanks for the comment. The basalt fibers mixed evenly are presented in the form of monofilaments in the concrete. The fibers absorb water and react with the cement to hydrate, and the generated cementitious materials can fill the pores. However, the fibers in the figure are not evenly dispersed into monofilaments, but in bundles. Because the fibers have water absorption, the water cement ratio is large, and the strength of the generated cementitious materials is low. The fibers can not bond well with the matrix and are prone to fall off, It is a clerical error to say that hydration products can't fill pores. The key point is to explain that agglomerated fibers will have a negative impact on strength. The original text has been revised.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments:

Page 1. Line 20. The abbreviation CT is not defined.

The authors of the article should point out the novelty of their research compared to the results of other authors and References [14, 22-26].

The article should be supplemented with information about the number of specimens in each series (OC, RC, and BFRC). Additionally, the results of compressive strength and splitting tensile strength should be provided for each specimen in each test series and also the average values of the strengths of each series with the standard deviation and variation of the results in a separate Table.

Page 3. Lines 92-93. Information about rubber particles and basalt fibers is poor. Therefore, more mechanical and geometric properties of rubber particles and basalt fibers should be provided in the text.

Page 3. Lines 111-113. It is not mentioned what was the age of the concrete during testing.

Page 6. Lines 195-196. Change "compressive strength" into splitting tensile strength.

Page 4. Lines 139-140. It is stated that "1700 slices with a spacing of about 58.86 μm were obtained from this scan. ". However, on Page 7. Lines 211-217, it is not mentioned what was the depth of the images in Figure 7.

Page 7. Lines 228-231. This sentence should be rewritten or divided into a couple of sentences to be clearer.

Page 8. Line 235-236. It states "Figure 9b shows that the porosity is higher in this region ....". It is not clear which region.

Page 9. Lines 270-273. The text needs to be rewritten to be clearer.

Author Response

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript sustainability-1881777. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. The main corrections in the paper and the responds to the reviewer’s comments are as following:

Comments:

Page 1. Line 20. The abbreviation CT is not defined.

Reply: Thanks for the comment. The abbreviation CT has been defined.

The authors of the article should point out the novelty of their research compared to the results of other authors and References [14, 22-26].

Reply: Thanks for the comment. The references have been described in detail and the innovation points of the article have been explained.

The article should be supplemented with information about the number of specimens in each series (OC, RC, and BFRC). Additionally, the results of compressive strength and splitting tensile strength should be provided for each specimen in each test series and also the average values of the strengths of each series with the standard deviation and variation of the results in a separate Table.

Reply: Thanks for the comment. Relevant data have been supplemented in Table 5 and Table 6.

Page 3. Lines 92-93. Information about rubber particles and basalt fibers is poor. Therefore, more mechanical and geometric properties of rubber particles and basalt fibers should be provided in the text.

Reply: Thanks for the comment. The performance parameters of basalt fiber rubber particles have been supplemented, see Table 2 and Table 3

Page 3. Lines 111-113. It is not mentioned what was the age of the concrete during testing.

Reply: Thanks for the comment. Concrete age has been added in line141.

Page 6. Lines 195-196. Change "compressive strength" into splitting tensile strength.

Reply: Thanks for the comment. The compressive strength has been changed to the splitting tensile strength.

Page 4. Lines 139-140. It is stated that "1700 slices with a spacing of about 58.86 μm were obtained from this scan. ". However, on Page 7. Lines 211-217, it is not mentioned what was the depth of the images in Figure 7.

Reply: Thanks for the comment. The image depth is the depth of the test block scanned by CT, as shown in Figure 2.

Page 7. Lines 228-231. This sentence should be rewritten or divided into a couple of sentences to be clearer.

Reply: Thanks for the comment. The original text has been revised.

Page 8. Line 235-236. It states "Figure 9b shows that the porosity is higher in this region ....". It is not clear which region.

Reply: Thanks for the comment. Areas with high porosity have been marked in the original text, see lines 295-298.

Page 9. Lines 270-273. The text needs to be rewritten to be clearer.

Reply: Thanks for the comment. The content of the article has been modified.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The questions mentioned last time have been answered.

Reviewer 3 Report

Table 5 "Average splitting tensile strength" should be changed with compressive strength.