Study on the Long-Term Durability and Leaching Characteristics of Low-Consumption Cement Backfill under Different Environmental Conditions
, Liuhua Yang 1, Tongyi Yang 3, Chunlai Wang 4 and Xiaohui Liu 5
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsIn this paper, the long-term leaching amount of four heavy metals and the strength change of filling body were studied by simulating the soaking environment of low-consumption cement filling body in different acidic and alkaline groundwater. Under the premise of ensuring the safety of filling body structure, the critical value of cement consumption under environmental pollution can be effectively prevented, and the green economic benefit of filling technology can be maximized. This paper is rich in content, compact in structure, reasonable and scientific in experimental design, and accurate in analysis. However, there are also some problems in the paper. The language is not concise enough, the expression is not clear enough, the words have spelling errors, and the grammatical structure also has certain problems. Please read and check carefully. In addition, the following suggestions are made for the content of the paper:
（1） ' PH ' should be replaced by ' pH'；
（2） The introduction part in the background is too cumbersome, please directly introduce the theme of this paper to study;
（3） In describing the research status, please point out the shortcomings of previous studies and the problems you need to solve；
（4） In section 3.3.4, the analysis of the leaching characteristics and solidification mechanism of Ni should be in the same order as that of other heavy metals. The leaching characteristics of heavy metals should be analyzed first and then the solidification mechanism should be analyzed；
（5） In section 3.4.2, please explain why only the leaching of heavy metals in the filling body with a cement-sand ratio of 1:15 is selected as the first-order model of reaction diffusion.
（6） In the conclusion, the summary language is used to describe the characteristics of the leaching amount of heavy metals in the filling body with the change of pH and cement consumption；
（7） The conclusion should summarize the influence of pH and cement consumption on the durability of filling body；
（8） Whether this study has shortcomings, how to improve it, what is the future research direction, and clarify these will help to enhance the scientific reference value of the literature.
Comments for author File: 
Comments.pdf
The English quality of the whole article is relatively good.
Author Response
Dear Reviewer：
We would like to express our sincere thanks to you for your overall commenting. Thank reviewers for giving a chance to revise this manuscript.
We have attached great importance to this opportunity to revise the manuscript.We have revised the manuscript. In the revision, we take full consideration of the reviewer's suggestions, so that the manuscript can be better presented and analyzed.
The revised detail is as follow.
1. The comment put forward by the reviewer is very helpful. This is a detail problem. We carefully checked, the word 'pH' in the manuscript has been completely changed to 'pH', which makes the paper professional has been improved.
2. This comment from the reviewer increases the readability of the paper. In the first paragraph of the introduction, the paper describes the development of modern mining too much, deviates from the research theme of the paper, and the background introduction is more cumbersome. In order to solve this problem, we have made great changes to the relevant content. The first part of the paper is simplified from 'With the contemporary industry 's fast development' to 'As a novel reshaping to achieve environmentally friendly and sustainable mining resource development'. The development of cemented tailings backfilling technology is summarized in a short language, and the current environmental and structural problems are introduced.
3. The reviewer's comment clarifies the research direction of the paper. In the second paragraph of the introduction, we reviewed the research progress of Suwimol Asavapisit、Choon Keun Park、M. Tyrer、Rachana Malviya and other scholars on the ability of cement consumption to solidify heavy metals, and pointed out that previous studies have failed to determine the minimum cement consumption for effective solidification of heavy metal ions. We will explore the critical value of effective control of heavy metal leaching and diffusion cement consumption. In the third paragraph of the introduction, we summarized the effects of pH on the leaching of heavy metals by Joris J.Dijkstra, Souhail R.Al Abed, Andreas Voegelin et al., and pointed out that the research on the low-intensity solidification ability of CTB has not been carried out.
4. This reviewer's comment has enhanced the structure of the paper. The analysis sequence of research results in section 3.3.4 has been changed. the analysis of the leaching characteristics and solidification mechanism of Ni should be in the same order as that of other heavy metals. The leaching characteristics of heavy metals should be analyzed first and then the solidification mechanism should be analyzed.
5. The reviewer's comment is very valuable. The leaching of various heavy metals in CTB with a cement-sand ratio of 1:15 was selected as the first-level model because the cement consumption of the CTB meets the requirements of environmental cleaning and structural safety. The reason for selecting the leaching of various heavy metals in the CTB with a lime sand ratio of 1:15 as the first-order model has been explained in the middle of the first paragraph of 3.4.2.
6. The reviewer's comment is a summary of the research results, which is the core and key content of the paper. The characteristics of the leaching amount of heavy metals in the CTB with changes in cement consumption and pH are pointed out in conclusions 1 and 2, respectively. The decrease in cement consumption. The decrease of cement consumption leads to the decrease of the solidification ability of the filling weight metal, and the leaching of heavy metals is easier. Both acidic and alkaline environments are not conducive to the long-term stability of heavy metals, and heavy metals are easier to leach.
7. The reviewer's comment is a summary of the research results, which is the core and key content of the paper. The characteristics of the leaching amount of heavy metals in the CTB with changes in cement consumption and pH are pointed out in conclusions 1 and 2, respectively. With the decrease of cement consumption, the long-term durability of CTB is gradually weakened. In the environment with stronger acid/alkaline, the effect of acid/alkaline erosion is more obvious, which will accelerate the dissolution of hydration products in CTB and reduce the durability of the CTB.
8. The reviewer's comment is very valuable and clarify the next research direction. Future research directions are proposed at the end of the conclusion. In the future, the range of critical values for cement consumption will be further narrowed, and the mechanism of heavy metal ion infiltration and leaching will be explored in depth. At the same time, the strength of CTB will be controlled by changing process parameters and other methods, and applied to mining practice.
In addition, format, word spelling, and grammar of the manuscript have been corrected. Other modification details and changes are marked in the manuscript.
We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper.
We earnestly appreciate for Editors/Reviewers’ work and hope that the correction will meet with approval.
Once again, thank you very much for your comments and suggestions. Should you have any questions, please contact us without hesitation.
Best regards, Yours sincerely, Huazhe Jiao E-mail：jiaohuazhe@hpu.edu.cn
Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe article is devoted to an important and topical issue related to the analysis of the characteristics of the leaching process when consuming cement backfill under various conditions.
In the world practice of mining, the role of geotechnologies with the filling of mined-out space with hardening mixtures is increasingly increasing. The constant increase in the volume of mineral extraction raises the practical need to solve the problem of disposing of the growing volumes of mining waste. Tightening the requirements of environmental legislation and economic sanctions for damage to nature, especially in areas of successful farming, may lead to a complete cessation of mining operations in some regions. The use of mining systems with backfill opens up wide opportunities for recycling in the mined-out space not only the mining and processing enterprise’s own waste, but also waste from metallurgical, energy and chemical industries, while ensuring minimal deformation of the undermined massif and the preservation of the earth’s surface. In addition, the use of hardening fill in underground mines allows: to successfully solve the problem of managing rock pressure, reducing the potential danger of its manifestation in static and dynamic forms; revise the traditional standards for opening and preparing deposits for exploitation, bringing the shafts closer to the ore deposits, minimizing the volume of rock crosscutting and the distance of underground transport of mined ore; master the ascending order of mining deposits without leaving security and other pillars for various purposes; increase several times the completeness and quality of ore extraction from the subsoil. However, there are certain economic limitations to the widespread development of this advanced technology. In most cases, specially mined aggregate and Portland cement, which have a high cost, are used to form the backfill mass. In some areas, even obtaining filler can be a difficult economic problem to solve. At the same time, many of the accumulated waste products can be effectively used not only as fillers, but also as binding materials. In recent years, the possibility of partial and often complete replacement of cements with other materials has been identified. The need to improve existing backfill complexes and technologies for the development of mineral deposits with the backfilling of mined-out space with hardening mixtures based on enrichment tailings led to comprehensive research.
The work reviewed is of relevance and importance and will be of interest to readers in the field under consideration.
However, a number of comments about the article should be clarified:
1. In the introduction, insufficient attention is paid to the issues of disposal of tailings formed as a result of mining, using modern methods, in particular those related to the reuse and mechanochemical processing of ore tailings.
2. It is necessary to dwell in more detail on the equipment that was used to conduct complex experimental studies.
3. What does the XRD analysis technique for studying gold tailings include (Figure 2)? It should be clarified whether the chemical analysis of technogenic raw materials was carried out using X-ray fluorescence and spectral methods, and whether the atomic emission spectral method with inductively coupled plasma was used?
4. Is a wider range of changes in the considered characteristics of ambient air allowed (section “2.2 Sample preparation”)?
5. It is necessary to present a research methodology based on the results given in section “2.3 Testing method”, for which a corresponding patent could be obtained.
6. The quality of figures 7 should be improved and the letter designations should be increased.
7. According to the data shown in Figures 10, 12, it is necessary to present the corresponding mathematical models that allow the calculation and prediction of the output values under consideration.
8. It is necessary to conduct a more complete comparative analysis between the various elements (Table 6), since the results presented in Figure 18 are of significant interest and have high practical significance.
9. Prospects for further research in the scientific direction under consideration should be presented.
Author Response
Dear Reviewer：
We would like to express our sincere thanks to you for your overall commenting. Thank reviewers for giving a chance to revise this manuscript. We have attached great importance to this opportunity to revise the manuscript.
We have revised the manuscript. In the revision, we take full consideration of the reviewer's suggestions, so that the manuscript can be better presented and analyzed.
The revised detail is as follow.
1. The opinion put forward by the reviewer is very helpful. It can make our background introduction more perfect. According to the reviewer 's opinion, we made a summary in the introduction. With the promotion of green and sustainable development in global mines as a novel technology to achieve environmentally friendly and sustainable mining resource development, the cemented tailings backfilling technology has been continuously improved and promoted, and has become the preferred way to deal with tailings.
2. The reviewer 's opinion is necessary, which can make the experimental study of the experimental studies more clear. We have added a new section 2.2.1 to dwell in more detail on the equipment that was used to conduct complex experimental studies. Refer to the Solid waste–Determination of 22 metal elements–Inductively coupled plasma opticalemission spectrometry test method. ICP-AES test refers to the Solid waste–Determination of 22 metal elements–Inductively coupled plasma optical emission spectrometry test method. To measure the content of heavy metals in the sample, it is necessary to establish the corresponding standard curves of four heavy metal elements.
3. This opinion of the reviewer can increase the scientific nature of the paper. We use XRD analysis technique to detect the mineral composition of tailings and the hydration products inside the CTB. We use X-ray fluorescence and spectral methods to detect gold tailings' primary chemical makeup. The mineral composition of hydration products w-as analyzed by XRD. After the compressive strength test, the center of the specimen w-as sampled and the hydration of the model was stopped with anhydrous ethanol. The test angle is scanned between 10° and 90°. Both step size and emissivity are constant.
4. This opinion of the reviewer can make the logic of the paper more rigorous. We allow for a wider range of changes in the considered characteristics of ambient air. A humid air with constant temperature (20°±5°) and constant humidity (more than 90%).
5. This opinion of the reviewer is a high refinement of the value of the paper. Based on the reviewer's suggestions, we are proposing corresponding research methods and obtaining a corresponding patent based on the research results in“2.3 Testing method”.
6. The reviewer 's opinion is able to improve the quality of XRD diagrams of CTB and display the test results more intuitively and clearly. The quality of Figure 7 has been improved, and the relevant letter designations are marked in the figure.
7. This opinion of the reviewer is valuable, and it is a further exploration of the test results, which can enhance the scientific value of the paper. According to the data shown in Figure 10 and Figure 12, we presented the corresponding mathematical models as shown in Figure 18, which is used to calculate and predict the output value under consideration.
8. This opinion of the reviewer is an in-depth exploration of the results of the kinetics o-f leaching and can improve the value of the paper. In section 3.4.2, we conduct a mor-e complete comparative analysis between the various elements. We analyzed the dynamic evaluation o-f heavy metals in four heavy metal elements, analyzed the effective coefficient De, explored the factors affecting the leaching of heavy metals, analyzed the r-ate constant K value, explored the leaching ability of heavy metals, and analyzed the initial amount of soluble metals Q0, indicating the concentration of heavy metals in the initial amount of soluble metals.
9. The reviewer's comment is very valuable and clarify the next research direction. Future research directions are proposed at the end of the conclusion. In the future, the range o-f critical values for cement consumption will be further narrowed, and the mechanism of heavy metal ion infiltration and leaching will be explored in depth. At the same time, the strength of CTB will be controlled by changing process parameters and other methods, and applied to mining practice.
In addition, format, word spelling, and grammar of the paper have been corrected. Other modification details and changes are marked in the manuscript.
We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper.
We earnestly appreciate for Editors/Reviewers’ work and hope that the correction will meet with approval.
Once again, thank you very much for your comments and suggestions. Should you have any questions, please contact us without hesitation.
Best regards, Yours sincerely, Huazhe Jiao E-mail：jiaohuazhe@hpu.edu.cn
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsDear colleagues, you have undoubtedly strengthened the manuscript. Nevertheless, it is worth strengthening literature review a little and making some changes to increase the relevance of article for scientific community: 1) In annotation “thereby contributing to the sustainable development of green mines” it is better to replace with "thereby contributing to creation of sustainable mining geotechnologies." 2) Line 123. On PSD curve you need to write correct labels for coordinate axes “proportion totally” and “proportion respectively” (I didn't notice it at first). Let's call the Differential content (column on left) "Density distribution". Let's call integral content (column on the right) "Cumulative distribution". Then it will be like ISO 9276-1:1998. 3) Line 566. In FIG. 17 it is clear that you defined logarithmic types of dependencies and determined their formulas, but did not provide them further in manuscript. If you correct this, you will significantly strengthen your conclusions. 4) relevance of article for scientific community can be strengthened when used https://doi.org/10.3390/resources12100113; https://doi.org/10.1002/dug2.12070; https://doi.org/10.3390/ma16217004
Author Response
Dear Reviewer：
We would like to express our sincere thanks to you for your overall commenting. Thank reviewers for giving a chance to revise this manuscript. We have attached great importance to this opportunity to revise the manuscript.
We have revised the manuscript. In the revision, we take full consideration of the reviewer's suggestions, so that the manuscript can be better presented and analyzed.
The revised detail is as follow.
1. The comment put forward by the reviewer is very helpful. This is a detail problem. After careful consideration, we accept the author's proposal to replace" thereby contributing to the sustainable development of green mines" with "thereby contributing to creation of sustainable mining geotechnologies".
2. The reviewer's comment make the paper more scientific and rigorous. According to the reviewer's opinion, on the PSD curve, we write the correct label for the coordinate axis, name the Differential content (left column) as "density distribution", and name the integral content (right column) as "cumulative distribution".
3. The reviewer's comment can enrich the content of the manuscript. We define the dependence of logarithmic types and can provide their formulas, but we want to reverse the parameters of leaching kinetics through graphical combination to verify the characteristics of heavy metal leaching, the formulas is not so important.
4. The reviewer's comment has enhanced the scientificity and readability of the paper. We adopt the reviewer's opinion and refer to the literature provided by the reviewer, which strengthens the relevance of the paper to the scientific community.
In addition, format, word spelling, and grammar of the manuscript have been corrected. Other modification details and changes are marked in the manuscript.
We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper.
We earnestly appreciate for Editors/Reviewers’ work and hope that the correction will meet with approval.
Once again, thank you very much for your comments and suggestions. Should you have any questions, please contact us without hesitation.
Best regards,
Yours sincerely,
Huazhe Jiao
E-mail：jiaohuazhe@hpu.edu.cn
Author Response File: Author Response.pdf
