Experimental Investigation on the Effect of Gold Tailings as a Partial Replacement for Sand in Concrete

Round 1

Reviewer 1 Report (Previous Reviewer 4)

Comments and Suggestions for Authors

After minor revision paper can be accepted.

Author Response

comment: After minor revision paper can be accepted

Response: 

I appreciate your efforts and professional guidance in reviewing the manuscript with ID_ sustainability-3152412 and your support towards the publication process. The required minor revision has been done and the corrected sections were highlighted in the manuscript. 

Reviewer 2 Report (Previous Reviewer 3)

Comments and Suggestions for Authors

I have reviewed the paper, and compared to the version I reviewed earlier, it is clearly an improved manuscript. The authors have answered to the points that were suggested. They have strengthened the description of experimental methods, superplasticizer dosages and explained the low risk of leaching of toxic heavy metals. It still seems to me that a more detailed microstructural analysis would have helped even more to improve the work. In any case the volume of experimental data presented is large and the applicability of the results obtained is manifest, as well as the interest for the scientific community.

A minor comment is that, in the description of the XRD study, the range of 2-theta degrees studied, the step size and the time per step could be added to complete the description of the study.

There are in some cases changes in the font size, which, in any case, can be resolved during the editorial check stage prior to publication. 

Author Response

Comment: 

I have reviewed the paper, and compared to the version I reviewed earlier, it is clearly an improved manuscript. The authors have answered to the points that were suggested. They have strengthened the description of experimental methods, superplasticizer dosages and explained the low risk of leaching of toxic heavy metals. It still seems to me that a more detailed microstructural analysis would have helped even more to improve the work. In any case the volume of experimental data presented is large and the applicability of the results obtained is manifest, as well as the interest for the scientific community.

A minor comment is that, in the description of the XRD study, the range of 2-theta degrees studied, the step size and the time per step could be added to complete the description of the study.

There are in some cases changes in the font size, which, in any case, can be resolved during the editorial check stage prior to publication. 

Response: I appreciate your efforts and professional guidance in reviewing the manuscript with ID_ sustainability-3152412 and your support towards the publication process. I have revised the manuscript based on your comments and the corrected sections were highlighted in the manuscript.

Correction: The step size and time per step have been included and can be found in lines 139 and 140. 

Reviewer 3 Report (Previous Reviewer 2)

Comments and Suggestions for Authors

After carefully reviewing this manuscript, I also noticed some areas that need to be improved. I hope to provide some useful suggestions in this review to help you further improve your article:

(1) Some pictures are not clear enough, such as Figure 3, 16, it is recommended to replace the high-definition pictures. In addition, it is necessary to appropriately add some pictures of the experimental process.

(2) In the experimental design, the gradient of tailings content needs to be supplemented with necessary explanations.

(3) Further detailed description of the concrete mix design and sample preparation process is recommended, in particular how to ensure the uniformity of SGT.

(4) When drawing relevant conclusions at the end of the paper, the conclusion is not very general and lacks in-depth analysis and discussion of the experimental results. Therefore, it is suggested to make a concise summary, which will help to better explain the innovation and significance of the research.

(5) It is suggested to increase the comparison between SGT and traditional sand and gravel in terms of economy and carbon emission.

(6) The effect of SGT ratio on the mechanical properties and fluidity of concrete is huge, so it is suggested to refer to the following article in the introduction.

[1] Wu A, Wang Y, Xiao B, et al. Key theory and technology of cemented paste backfill for green mining of metal mines[J]. Green and Smart Mining Engineering, 2024, 1(1): 27-39.

 [2] Yang, L.; Jia, H.; Wu, A.; Jiao, H.; Chen, X.; Kou, Y.; Dong, M. Particle Aggregation and Breakage Kinetics in Cemented Paste Backfill. Int. J. Miner. Metall. Mater. 2023, 220, 172–186. https://doi.org/10.1007/s12613-023-2804-5

 

Author Response

Response: I appreciate your efforts and professional guidance in reviewing the manuscript with ID_ sustainability-3152412 and your support towards the publication process. I have revised the manuscript based on your comments and the corrected sections were highlighted in the manuscript. Below are the comments received and the corresponding corrections made. 

Comment 1: Some pictures are not clear enough, such as Figure 3, 16, it is recommended to replace the high-definition pictures. In addition, *it is necessary to appropriately add some pictures of the experimental process.

Response 1: Figure 3 has been enlarged, and Figure 16 has been adjusted for better clearance.

Lines 209, 220, 245, and 261 contain pictures of some of the experimental processes.

Comment 2: In the experimental design, the gradient of tailings content needs to be supplemented with necessary explanations.

Response 2: The additional information on the gradient of tailings content has been included and can be found in lines 173 – 176.

Comment 3: Further detailed description of the concrete mix design and sample preparation process is recommended, in particular how to ensure the uniformity of SGT.

Response 3: Further description has been included and can be found in lines 173 – 176 and 183 – 185.

Comment 4: When drawing relevant conclusions at the end of the paper, the conclusion is not very general and lacks in-depth analysis and discussion of the experimental results. Therefore, it is suggested to make a concise summary, which will help to better explain the innovation and significance of the research.

Response 4: The conclusion at the end of the paper (Section 5) has been revised according to the suggestion.

Comment 5: It is suggested to increase the comparison between SGT and traditional sand and gravel in terms of economy and carbon emission.

Response 5: The comparison in terms of economy and carbon emission has been included. It can be found in lines 677 – 683 (Section 5). 

Comment 6: 

The effect of SGT ratio on the mechanical properties and fluidity of concrete is huge, so it is suggested to refer to the following article in the introduction.

[1] Wu A, Wang Y, Xiao B, et al. Key theory and technology of cemented paste backfill for green mining of metal mines[J]. Green and Smart Mining Engineering, 2024, 1(1): 27-39.

 [2] Yang, L.; Jia, H.; Wu, A.; Jiao, H.; Chen, X.; Kou, Y.; Dong, M. Particle Aggregation and Breakage Kinetics in Cemented Paste Backfill. Int. J. Miner. Metall. Mater. 2023, 220, 172–186. https://doi.org/10.1007/s12613-023-2804-5

Response 6: The articles have been referred to and can be found in line 73.

Round 2

Reviewer 3 Report (Previous Reviewer 2)

Comments and Suggestions for Authors

The article has been revised according to the existing modification suggestions. The overall innovation of the article is obvious, the sentences are smooth, the vocabulary is reasonable, and the conclusion is clear and explicit. 

Comments on the Quality of English Language

Minor editing of English language required.

Author Response

Thank you for your efforts and professional guidance in reviewing the manuscript with ID_ sustainability-3152412, and for your support throughout the publication process.

Comment: Minor editing of English language required.

Response: The necessary minor edits of the English language have been completed.

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

Comments and Suggestions for Authors

The general assessment is that the study it is clear, the research is well conducted, the methodology is correctly stated, and the results and conclusions justified with the procedure. Moreover, the matter is within the topic of the journal.

Although I am not a native speaker, I find that the English language used in the manuscript is good enough.

The amount of literature reviewed is considered adequate, and the study can be considered up to date. There are some more articles that have conducted research relevant to the topic, please incorporate and discuss their findings in the introduction: 10.1016/j.wasman.2024.03.033; 10.1016/j.jmrt.2024.03.191.

In methodology, it must be clearly stated the number of specimens for each test, now in some tests it is not.

The discussion about whether to add a superplasticizer is unnecessary (naturally, workability is lower without it!). Please remove from the discussion the mixes without superplasticizer and consider them as a preliminary phase of your investigation. Additionally, include the TYPE AND PERCENTAGE OF SUPERPLASTICIZER used in the mix design.

In figures 3.3 and 3.4, only mean results are included, there was only one specimen performed or the deviation is missing.

MINOR MISTAKES

·       Check missing corresponding author in line 7

·       I don´t know if it is not required in this journal, but Highlights are not provided. Moreover, there are no sections in the paper regarding the author contributions or funding received.

·       Check numbering of figures and tables, it is not according to journal’s requirements.

·       Review the table formats; the spacing and font size are too large; all tables should be more compact.

·       Add to table in line 119 the sizes of the aggregates.

·       Check formatting errors in lines 177,183 and 197.

·       Try to put table in line 218 as horizontal, to be more compact.

·       Figures 3.6 and 3.8 are blurry.

Reviewer 2 Report

Comments and Suggestions for Authors

The paper does not seem particularly innovative and present several gaps in the experimental part.

Therefore I do not think it should be published in this journal.

Reviewer 3 Report

Comments and Suggestions for Authors

The paper presents results on the partial replacement of sand in concrete with gold mining waste. The structure of the paper is correct and the results offer an interesting alternative for recycling waste materials.

However, there are some points that should be improved before the work can be accepted. They are summarized in three main problems and detailed in other specific comments. The three main problems are:

1.            The description of some experimental methods and mix compositions (in particular the dosage of superplasticiser) is insufficient and needs to be improved.

2.            The presence of minor amounts of classical metallic elements in gold mines, some of them with potential toxicity, has not been considered, probably due to insufficient characterization of the waste materials. The inclusion of these elements and their potential leaching could compromise the applicability of the results of this work.

3.            Microstructural characterization is very scarce or even non-existent. In particular, there are no pore structure distribution measurements or SEM analysis of the hardened samples. This makes some discussions somewhat speculative and without experimental support.

Specific comments:

- Lines 91-94. Please provide more details about the experimental tests carried out (describe briefly the standards and also give details on the XRD and SEM measurement conditions)

- According to line 123, please in Table 2.1 add information on the exact dosage of superplasticizer used in each mix. This acquires more importance considering the discussion in section 3.2 about workability. Please, also consider the dosages of SP in the recorded slump values.

- Section 2.4: revise and correct the numbering of the subsections.

- Section 3.1. How were the values of the chemical composition of the sands obtained? By X-ray fluorescence?... Please, specify and provide in the Materials & Methods section the pertinent information on the experimental procedure.

- Being a mining waste, the presence in SGT of metallic elements (with likelihood some of them toxic) must be expected. A complete chemical description of the SGT composition should be included.

- Lines 211-25. XRD pattern of the SGT is not provided. The origin of the quantitative assessment of the SGT mineralogical composition is unknown. Please, complete all these aspects.

- Discussion in section 3.4 use logical reasoning but not experimentally proved. The filling effect, the changes in porosity and the interaction between cement paste and SGT particles might be assessed by mercury intrusion porosimetry and SEM examination.

- Regarding section 3.7.1, the data in figure 3.9 have such large error bars that the interpretation of the results is very difficult. The authors do not comment on this point, but it should be pointed out, because the interpretation of results must be very cautious. It should also be explained why the deviations are so large.

Reviewer 4 Report

Comments and Suggestions for Authors

Comments for author File: Comments.pdf