Developing Environmentally Sustainable and Cost-Effective Geopolymer Concrete with Improved Characteristics

Round 1

Reviewer 1 Report

The purpose of this experimental study is to obtain geopolymer fine-grained concrete with proved quality characteristics while having environmental friendliness and efficiency from the economic feasibility of producing such concrete and its advantages over competing analogues. The author found the most effective activator is a composition of NaOH and Na2SiO3 with a ratio of 1: 2 or the temperature of heat treatment has a positive effect on the kinetics of strength gain. These are not really surprising as they have been well documented in literature. The main problem is that the innovative points of this article are insufficient. I am afraid that I will refuse its publication in this journal, and I look forward to your other novel research to share with us.  In addition, there were no experiments with regard to the durability behaviour of the produced concrete. However, it is crucial to improve the understanding of the durability of alkali-activated and geopolymer materials in different conditions to be applied in civil construction

Author Response

Dear Reviewer!

Thanks for your valuable comment!

I'm sure this will make the article better and more readable.

 

1. The purpose of this experimental study is to obtain geopolymer fine-grained concrete with proved quality characteristics while having environmental friendliness and efficiency from the economic feasibility of producing such concrete and its advantages over competing analogues. The author found the most effective activator is a composition of NaOH and Na₂SiO₃ with a ratio of 1: 2 or the temperature of heat treatment has a positive effect on the kinetics of strength gain. These are not really surprising as they have been well documented in literature. The main problem is that the innovative points of this article are insufficient. I am afraid that I will refuse its publication in this journal, and I look forward to your other novel research to share with us.  In addition, there were no experiments with regard to the durability behaviour of the produced concrete. However, it is crucial to improve the understanding of the durability of alkali-activated and geopolymer materials in different conditions to be applied in civil construction

Dear reviewer, thanks for your comment.

The article has been entirely revised.

The Abstract (lines 17-33), the article goals (lines 183 - 186), scientific novelty (lines 200-208), results (lines 367-383, 426-432, 434, 435, 442-446, figure 12, figure 13) and Conclusions (lines 515-536) are revised. So, the main scientific and practical results and achievements of the authors, which are novelty, are formulated and expressed.

As for durability, we agree with your thesis about the importance of the durability indicator for geopolymer concretes, and this is the goal of our future research carried out in the development of the data already obtained on the new composition we have developed.

 

Finally, we would like to thank you for your valuable comment, attention to our work, and your support.

Reviewer 2 Report

Comments for “Developing Environmentally Sustainable and Cost Effective Geopolymer Concrete with Improved Characteristics”

Despite the main idea of the paper is initially interesting; it is necessary more measurements and devices to characterize the beams and provide some information about the final products and raw materials. The sources of data are not clear at all. This work needs a rethinking process to get a more interesting point of view and innovative conclusions.

Here there is some of the problems I found in the text:

In chapter 1.2. Literature review on the research topic, in some references I think should be convenient to mention the name of the reference´s researcher author of [25], [26], [27], [28], [29] and [30] references.

Figure 1 presents some graphic defects, probably due to the exportation of the image.

The surname of the researcher “Joseph Davidovits” is misspelled in lines: 128, 133, 140, 150, 162 and 175

In line 175, the authors mention Figure 3 when it is Figure 2.

In 2.2 Materials chapter, the devices employed to obtaining the Physical characteristics and Chemical compositions exposed in the work are not described.

In line 357, it seems the expression should be: “but the results give an unambiguous conclusion about this”

The sentence in line 361: “It is known that sodium hydroxide is responsible for the destruction of the internal bonds of the binder at the beginning of the process, and then sodium silicate activates the necessary bonds between the binder and aggregates.” it should be referenced with some previous work.

In Figures 7, 8, 9 and 10, the compressive and tensile flexural strengths are fitted through a potential equation of 6^th grade. Have you tried to adjust the results with a lower degree of potential equation, checking if the R² still being acceptable?

Figure 11, 12 and 14 are not labeled and have not description or legend but they are referred in the text.

In the heat treatment process, it is not specified how long the treatment was.

The sentence in line 422: “A visual assessment of these compositions demonstrates the formation of structural deformations (cracks, chips) in the studied samples of geopolymer fine-grained concrete.” could be accompanied with some pictures of the deformations.

In line 448, “it is required to spend half the energy (Figure 13a)”, the Figure 13a shows the energy cost in a relative way, so we cannot see the reference to say that the geopolymer binders employs “half of the energy”

The authors do not indicate where the data of Figure 13 came from. Besides, that Figure is quite confused.

The sentence in line 459: “In the production of geopolymer binders, carbon dioxide emissions into the atmosphere are 3 ... 4.5 times lower than in the production of Portland cement (Figure 13c).” says the reverse that we can find in the Figure 13c.

Figure 14 requires some longer description and authors explaining to understand the most important factors of the scheme

Comments for author File: Comments.pdf

Author Response

Dear Reviewer!

Thanks for your valuable comment!

I'm sure this will make the article better and more readable.

 

1. In chapter 1.2. Literature review on the research topic, in some references I think should be convenient to mention the name of the reference´s researcher author of [25], [26], [27], [28], [29] and [30] references.

Dear Reviewer, thanks for your comment.

The names of the authors corresponding to the indicated links (lines 73, 80, 87, 97, 103, 111) have been added. Due to a technical error, the numbering of these references has shifted by +1 in accordance with References (lines 605-620) We fixed this mistake.

2. Figure 1 presents some graphic defects, probably due to the exportation of the image.

Dear Reviewer, thanks for your comment. To eliminate possible defects, we inserted the picture again in the updated file. Perhaps, there was a technical mistake.

3. The surname of the researcher “Joseph Davidovits” is misspelled in lines: 128, 133, 140, 150, 162 and 175.

Dear Reviewer, thanks for your comment. The surname of the researcher Joseph Davidovits was corrected (lines 130, 135, 142, 152, 164, 177).

4. In line 175, the authors mention Figure 3 when it is Figure 2.

Dear Reviewer, thanks for your comment.

We corrected text (line 178).

5. In 2.2 Materials chapter, the devices employed to obtaining the Physical characteristics and Chemical compositions exposed in the work are not described.

Dear Reviewer, thanks for your comment. The chemical composition, physical and mechanical characteristics of raw materials for the projected composition of geopolymer concrete were taken equal to the data declared by the manufacturers in the quality certificates. Therefore, the text is supplemented at line 264.

6. In line 357, it seems the expression should be: “but the results give an unambiguous conclusion about this”

Dear Reviewer, thanks for your comment. The wording has been changed (line 361).

7. The sentence in line 361: “It is known that sodium hydroxide is responsible for the destruction of the internal bonds of the binder at the beginning of the process, and then sodium silicate activates the necessary bonds between the binder and aggregates.” it should be referenced with some previous work.

Dear Reviewer, thanks for your comment. Links to the specified text fragment (line 366) have been added.

8. In Figures 7, 8, 9 and 10, the compressive and tensile flexural strengths are fitted through a potential equation of 6th grade. Have you tried to adjust the results with a lower degree of potential equation, checking if the R2 still being acceptable?

Dear Reviewer, thanks for your comment. Figures 7-10 show the equations that most accurately reflect the mathematical model of these dependencies. Equations containing polynomials with a lower degree do not give such a high coefficient of determination. The determination coefficient drops to 0.7-0.8, and the function at the boundaries is unstable.

9. Figure 11, 12 and 14 are not labeled and have not description or legend but they are referred in the text.

Dear Reviewer, thanks for your comment. In the version of the article sent to the editorial office, the file with the .docx extension contains captions for all figures. When converting to the PDF version, due to a software error, the inscriptions to the three figures indicated disappeared. Corrected.

10. In the heat treatment process, it is not specified how long the treatment was.

Dear Reviewer, thanks for your comment. The data on the duration of the heat treatment was added to the text of the article (line 423).

11 The sentence in line 422: ”A visual assessment of these compositions demonstrates the formation of structural deformations (cracks, chips) in the studied samples of geopolymer fine-grained concrete.” could be accompanied with some pictures of the deformations.

Dear Reviewer, thanks for your comment. Figure 13 has been added, which demonstrated cracks and chips.

12. In line 448, “it is required to spend half the energy (Figure 13a)”, the Figure 13a shows the energy cost in a relative way, so we cannot see the reference to say that the geopolymer binders employs “half of the energy”.

Dear Reviewer, thanks for your comment. The phrase has been deleted. The incorrect drawing has been deleted.

13. The authors do not indicate where the data of Figure 13 came from. Besides, that Figure is quite confused.

Dear Reviewer, thanks for your comment. A source link has been added to the text (line 482).

14. The sentence in line 459: “In the production of geopolymer binders, carbon dioxide emissions into the atmosphere are 3 ... 4.5 times lower than in the production of Portland cement (Figure 13c).” says the reverse that we can find in the Figure 13c.

Dear Reviewer, thanks for your comment. The figure was corrected and brought in line with the text (Figure 14b).

15. Figure 14 requires some longer description and authors explaining to understand the most important factors of the scheme.

Dear Reviewer, thanks for your comment. A detailed description of Figure 15 (lines 496-507) has been added. A branch numbering in Figure 15 has been added for convenience. The significance of the factor is not assessed in this diagram. In the presented diagram, all factors are important for the formation of the final quality of geopolymer concrete.

 

Finally, we would like to thank you for your valuable comment, attention to our work, and your support.

Round 2

Reviewer 1 Report

The authors addressed all the comments. 

Author Response

Dear Reviewer!
Thanks for your kind comments and support! 
I'm sure your remarks have made the article better and more readable.

Reviewer 2 Report

A large number of minor errors have been remedied, as the references, errors in the Figures and main data as oven time. However, the article still being poor regarding to the measurements and the experimental part.

Despite of the chemical composition of the raw material employed is obtained from the manufacturers; some experiments to corroborate this data should be done. XRF and/or XRD could help to give a better idea of the “as received material” compositions and Laser granulometry could confirm the grain size of the aggregates.

Maybe XRD, FT-IR or/and SEM images could help to improve the conclusions of the article.

 

Comments for author File: Comments.pdf

Author Response

Dear Reviewer!

Thanks for your valuable comment!

I'm sure this will make the article better and more readable.

 

1. Despite of the chemical composition of the raw material employed is obtained from the manufacturers; some experiments to corroborate this data should be done. XRF and/or XRD could help to give a better idea of the “as received material” compositions and Laser granulometry could confirm the grain size of the aggregates.

Dear reviewer, thanks for your comment.

We have carried out additional studies and their results are presented in an extended version of the article. The granulometry of the grains was evaluated and their compliance with the characteristics declared by the manufacturer was confirmed (Figure 4, lines 279-283, Table 6).

2. Maybe XRD, FT-IR or/and SEM images could help to improve the conclusions of the article.

SEM analysis has been performed and presented in the text (Figure 13, lines 426-445) and XRD has been shown (Figure 3, lines 273-278).

The Conclusion section has been supplemented with a new paragraph on SEM microstructure analysis.

Finally, we would like to thank you for your valuable comment, attention to our work, and your support.

Round 3

Reviewer 2 Report

Once the materials as received are characterized and the authors improved the results with more techniques, I have not more comments about the article