Experimental Study on the Physical and Mechanical Properties of Cemented Gangue Backfill under Acid Mine Water Erosion
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis paper investigated the mechanical properties of cemented gangue backfill (CGB) under different chemical erosion time using acoustic emission (AE) technique. AE parameter analysis was performed for determining the stress thresholds for microcrack initiation and macrocrack extension. The topic of this manuscript is interesting. Following shortages must be overcomed before publication for improving the overall quality of the manuscript.
1. Because AE analysis is a very important part in your manuscript, it is necessary to provide the details of AE monitoring such as the type of AE system and sensor, and the method for eliminating the noise.
2. In section 3.3.1, three stages. i.e., the initial, calm, and active stage were identified based on the evolution of AE count. However, in section 3.3.2, four stages were discriminated from results of AE count. This seems to confuse the readers and the authors should give the reason.
3. In Figure 6 (a-c, e), how did you discriminate stage 3 and stage 4 because there is not an evident change in the slope of cumulative AE count. It is also not clear for readers how to discriminate stage 2 and 3 in Figure 6(f).
4. Can you provide direct evidence that stage 2 in Figure 6 is caused by microcrack nucleation?
5. In addition to count, there are many time-domain features that can be extracted from AE waveform such as energy, information entropy, RMS and so forth. The combined use of different features is helpful for identifying different damage stages during mechanical loading. However, the authors only calculated the count and did not extract more features and tie them with the stress or the erosion time. The authors are suggested to use multiple AE parameters in identifying different stages in your experiments, or they should at least discuss it. Regarding the extraction of time-domain AE features and their use in damage identification, the reviewer recommends the authors to cite the following papers and discuss more features.
https://doi.org/10.1016/j.ijpvp.2023.104998
https://doi.org/10.1016/j.matdes.2020.109258
6. The authors claimed that“The acoustic emission characteristics of CGB loaded by chemical ion erosion have not been thoroughly investigated” in Introduction. Thus, the reviewer suggests the authors to add some AE results in the Conclusion part.
Comments on the Quality of English LanguageNo
Author Response
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Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsManuscript ID applsci-2724361 “Experimental Study on the Physical and Mechanical Properties of Cemented Gang Backfill under Acid Mine Water Erosion” submitted to Applied Sciences presents an experimental study on cemented gang backfill (CGB) originating from an underground mine of coal.
The work contemplates a detailed experimental study of the application of already well-established methods to characterize the physical and mechanical properties of CGB under controlled experimental conditions.
The manuscript is well structured scientifically, but it lacks a rigorous review of the writing, with several typing errors, the use of meaningless acronyms and words written in different ways, such as macrocracks and microcracks and macro-cracks and micro-cracks.
Several writing inaccuracies are highlighted in the annex.
The text is sometimes long-winded and repetitive and could be improved.
The figures need to be improved, making them clearer and more understandable for future readers.
It is important to always separate numerals from units, whether in the text, figures and tables.
Discussions can be improved through greater scientific support based on literature and comparison of data with those from other similar scientific works, especially studies carried out in other countries.
References can and should include the respective DOI.
Reference number 4 is incomplete.
Comments for author File: Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript submitted for review entitled "Experimental Study on the Physical and Mechanical Properties of Cemented Gangue Backfill under Acid Mine Water Erosion" is a report from the conducted research of the effect of acid mine water erosion on the acoustic, mechanical properties of the Cemented Gangue Backfill (CGB). Overall, the manuscript is well structured and well written. I noticed several typographical issue that I mentioned in the minor points part of my review. The experiment method are relatively well explained, I think it missed some information and notably more detailed on the sulphuric acid solution (concentration, composition…). Some elements of the article need to be checked, improved and corrected, which will increase its quality. My main concern is relative to the mechanism discussion where some chemical description are not consistent with the external sulfate attack. In the same way, I think it could greatly improve the manuscript if the authors compared more their work with the external sulfate attack literature where the mechanism are relative closed.
Following I will detailed my review divided in major and minor points.
Major Points
- In the introduction, you specified that sulfate ions reaction with the hydration produce calcite. I did not understand this point and calcite is more a product of carbonation reaction. Furthermore, you do not mention this precipitation reaction on your mechanism discussion part. According to [Planel et al., 2006][El Hashen et al., 2012][Whittaker et al., 2015] sulfate reaction react with cement and precipitate in gypsum and ettringite as detailed in the mechanism part of your article. In the same way, you mentioned calcite in your conclusion.
- Your experiment seems to be similar to external sulfate attack with calcium leaching. It could be interesting to add more literature relative on this topic such as [Planel et al., 2006].
- The water/cement ratio was taken as 0.75 that is a value well higher than the industrial concrete. Is it a classic water cement ratio for concrete of CGB ? Such a huge water cement ratio induces a high porosity and a low mechanical properties. In that way, the swelling kinetic and the relative damage increase with the water cement ratio [El Hachem et al., 2012]
- Please detail the acid sulphuric solution, i.e., composition and concentration
- I do not find the number of sample. Furthermore, in the Figure 4 you indicated the average data value of the variation of CGB peak stress with the erosion time without mention the number of data.
- 4.2 you discussed about ettringite, why do you call calcium alumina phases ? You mentioned that ettringite reacted with the portlandite mineral but the main limiting reactant in external sulfate reaction are the Afm phases such as katoite mineral or monosulfoaluminate [Pouya et al., 2022][El Hashen et al., 2012]. Please add this information on the document and modified this section. Furthermore add references in this section.
- 4.3 you specified that gypsum lead to the swelling of the concrete. But that is also the case of the ettringite precipitation [Pouya et al., 2022][El Hashen et al., 2012]
- 4.4 I think your experiment is relative close to a calcium leaching and external sulfate attack reaction [Planel et al., 2006]. Maybe change the title Neutralization reaction of H+ by calcium leaching or cement leaching. Furthermore, the low pH induces the dissolution of hydrated mineral that reduced the mechanical properties. It could be interesting to distinguish the effect of the sulfate attack and leaching reaction on the mechanical behaviour.
- Line 358-360 you mentioned the dissolution of the ettringite due to leaching but some article [Planel et al., 2006][Pouya et al., 2022] discussed the presence of ettringite but the dissolution of portlandite and other phases in the same kind of chemical attack. Can you explain it ?
Minor Points
- Please introduce “CBG” notation line 36
- Typo issue line 44 “[6].According”
- Figure 6, please add the erosion time relative to each subfigure
- Even if you used fly ash maybe add the portlandite precipitation on the hydration product
- I did not understand the following sentence “ . In the specific chemical reaction equation, as shown in equations 7 and 8, along with the neutralization reaction, the generation of corrosion products that are readily soluble in water is dissolved away, making the penetration of the filling body to reduce the quality of the filling body, at the same time, filling the body of the structure of the hydration products and bonding interface strength are weakened (Fig. 8-f), filling the body as a whole is damaged, the macro-mechanical” (line 344-350). Please change the sentence
- There is not point at the end of the previous sentence
- Figure 8 please specified Hydration products on the image
- Line 390 “caliche” ?
References:
- Planel, D., Sercombe, J., Bescop, P. L., Adenot, F., & Torrenti, J. M. (2006). Long-term performance of cement paste during combined calcium leaching-suflate attack: Kinetics and size effect. Cement and Concrete Research, 36(1), 137–143. https://doi.org/10.1016/j.cemconres.2004.07.039
- El Hachem, R., Rozière, E., Grondin, F., & Loukili, A. (2012). Multi-criteria analysis of the mechanism of degradation of Portland cement based mortars exposed to external sulphate attack. Cement and Concrete Research, 42(10), 1327–1335. https://doi.org/10.1016/j.cemconres.2012.06.005
- Pouya J, Neji M, De Windt L, Péralès F, Socié A, Corvisier J. (2023) Mineralogical Evolution and Expansion of Cement Pastes in a Sulfate-Confined Environment. Minerals. 2023; 13(1):1. https://doi.org/10.3390/min13010001
Author Response
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Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsAfter revision, the manuscript can be published in the journal.
Comments on the Quality of English LanguageNo comment.
Reviewer 3 Report
Comments and Suggestions for AuthorsThank you for taking into account my several comments. I truly think the paper and most of all the mechanism discussion part gained into scientific context and pertinence by adding the sulfate attack literature.
