Trans-scale relationship analysis between the pore structure and macro parameters of backfill and slurry

The characteristics of the porous structure of backfill are directly related to the macro parameters of the flowability of the filling slurry and the mechanical features of the backfill, which are fundamental to the study of multiscale mechanics of backfill. Based on the geometry and fractal theory, scanning electron microscopy images of backfill were analysed by image analysis methods such as OTSU and box counting. The fractal dimension of the pore structure was calculated. By quantitatively characterizing the pore structure, the trans-scale relationships between the fractal dimension of the pore structure and the macro parameters of the filling slurry were established in terms of equilibrium shear stress (ESS) and equilibrium apparent viscosity (EAV). In addition, the correlations between the fractal dimension and macro parameters of backfill were obtained in terms of uniaxial compressive strength (UCS), water content (WC) and porosity. The influence of the microstructure on the macro parameters was discussed. The results show the following: (i) the fractal dimension of the backfill pore structure can characterize the complexity of the structure; (ii) the fractal dimension of the pore structure is negatively correlated with the ESS and EAV of the filling slurry. The UCS of the backfill is positively correlated with the flowability parameter; (iii) the fractal dimension of the pore structure has a certain correlation with some macro parameters of the backfill, i.e. the fractal dimension is negatively correlated with the UCS and positively correlated with the WC and (iv) the linear correlations between the pore fractal dimension and UCS and WC are established. The correlation coefficient between the fractal dimension and UCS has an R2 value of −0.638, while the corresponding value of the fractal dimension and WC is 0.604. UCS and WC can be predicted by the fractal dimension of pores.


Recommendation?
Accept with minor revision (please list in comments)

Comments to the Author(s)
The relation between micro porous structure and macro parameters of backfills is difficult to be quantitatively calculated. This paper shares a method through calculating the fractal dimension of pores. It is really an interesting topic. The major problem is the language. The English needs substantial editing. So I recommend that this paper can be published after language polish.

01-Apr-2019
Dear Dr Ren, The editors assigned to your paper ("Trans-scale relationship analysis between pore structure and macroparameters of backfill and slurry") have now received comments from reviewers. We would like you to revise your paper in accordance with the referee and Associate Editor suggestions which can be found below (not including confidential reports to the Editor). Please note this decision does not guarantee eventual acceptance.
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Comments to Author:
Reviewers' Comments to Author: Reviewer: 1 Comments to the Author(s) The research was carried out in a comprehensive way which gives sufficient credibility to the main results. The particular value of the paper is in its original approach for analysing the results. Interesting paper with an interesting approach that few researchers considered previously in this field. However, I would like to recommend the following improvements: 1. In the Matlab analysis for the obtained SEM micro-images, authors did not mention the dilemma of noise in the background. How authors managed to reduce the noise in the images for a proper analysis? -A novel approach of introducing crystalline protection material and curing agent in fresh concrete for enhancing hydrophobicity.
-Development of hydrophobic concrete by adding dual-crystalline admixture at mixing stage.
-Influence of early water exposure on modified cementitious coating.
The paper is very interesting and I recommend it for publication but after the authors rectify the comments.

Reviewer: 2
Comments to the Author(s) The relation between micro porous structure and macro parameters of backfills is difficult to be quantitatively calculated. This paper shares a method through calculating the fractal dimension of pores. It is really an interesting topic. The major problem is the language. The English needs substantial editing. So I recommend that this paper can be published after language polish.

Author's Response to Decision Letter for (RSOS-190389.R0)
See Appendix A.

Recommendation?
Accept as is On behalf of the Editors, I am pleased to inform you that your Manuscript RSOS-190389.R1 entitled "Trans-scale relationship analysis between the pore structure and macroparameters of backfill and slurry" has been accepted for publication in Royal Society Open Science subject to minor revision in accordance with the referee suggestions. Please find the referees' comments at the end of this email.
The reviewers and Subject Editor have recommended publication, but also suggest some minor revisions to your manuscript. Therefore, I invite you to respond to the comments and revise your manuscript.
• Ethics statement If your study uses humans or animals please include details of the ethical approval received, including the name of the committee that granted approval. For human studies please also detail whether informed consent was obtained. For field studies on animals please include details of all permissions, licences and/or approvals granted to carry out the fieldwork.
• Data accessibility It is a condition of publication that all supporting data are made available either as supplementary information or preferably in a suitable permanent repository. The data accessibility section should state where the article's supporting data can be accessed. This section should also include details, where possible of where to access other relevant research materials such as statistical tools, protocols, software etc can be accessed. If the data has been deposited in an external repository this section should list the database, accession number and link to the DOI for all data from the article that has been made publicly available. Data sets that have been deposited in an external repository and have a DOI should also be appropriately cited in the manuscript and included in the reference list.
If you wish to submit your supporting data or code to Dryad (http://datadryad.org/), or modify your current submission to dryad, please use the following link: http://datadryad.org/submit?journalID=RSOS&manu=RSOS-190389.R1 • Competing interests Please declare any financial or non-financial competing interests, or state that you have no competing interests.
• Authors' contributions All submissions, other than those with a single author, must include an Authors' Contributions section which individually lists the specific contribution of each author. The list of Authors should meet all of the following criteria; 1) substantial contributions to conception and design, or acquisition of data, or analysis and interpretation of data; 2) drafting the article or revising it critically for important intellectual content; and 3) final approval of the version to be published.
All contributors who do not meet all of these criteria should be included in the acknowledgements.
We suggest the following format: AB carried out the molecular lab work, participated in data analysis, carried out sequence alignments, participated in the design of the study and drafted the manuscript; CD carried out the statistical analyses; EF collected field data; GH conceived of the study, designed the study, coordinated the study and helped draft the manuscript. All authors gave final approval for publication.
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Kind regards, Andrew Dunn Royal Society Open Science Editorial Office Royal Society Open Science openscience@royalsociety.org on behalf of Prof R. Kerry Rowe (Subject Editor) openscience@royalsociety.org Associate Editor Comments to Author: The reviewer recommends the paper be accepted; however, the Editors asked you to seek language editing (https://royalsociety.org/journals/authors/language-polishing/) prior to resubmitting, and there is no evidence that the authors have done this. Please ensure that you seek advice on improving the written language of the paper --we can only publish once you've done this, and if you submit the revision without evidence from a qualified language editor that the paper has been edited for language, we will return the paper to you. I am pleased to inform you that your manuscript entitled "Trans-scale relationship analysis between the pore structure and macroparameters of backfill and slurry" is now accepted for publication in Royal Society Open Science.
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Details in revision according to reviewer's comments and suggestions on the manuscript "Royal Society Open Science RSOS-190389"
Title of paper: Trans-scale relationship analysis between pore structure and macroparameters of backfill and slurry Authors: Jianhua Hu 1 , Qifan Ren 1 , Xiaotian Ding 1 , Quan Jiang 1 We addressed the comments of the reviewer (with green color) with responses as listed below, corresponding to necessary changes, additional sentences and short sections at proper places which are marked by red color in the revised version of manuscript.
Editor Q1: Reviewer 2 has recommended that the quality of English should be improved. A number of language polishing services are available for authors whose first language is not English. https://royalsociety.org/journals/authors/language-polishing/ Response 4: The manuscript was polished by American Journal Experts. The Editorial Certificate is in the following.
Reviewer: 1 Q1-(Reviewer1): In the Matlab analysis for the obtained SEM micro-images, authors did not mention the dilemma of noise in the background. How authors managed to reduce the noise in the images for a proper analysis?
Response 1: Yes, the noise in background is a dilemma. So I testes many methods to obtain ideal results. The details are as follows. The content has been added in section 3.3 SEM image preprocessing.

SEM image preprocessing
Image preprocessing mainly includes two aspects of image contrast adjustment and noise reduction.

Image contrast adjustment
Contrast adjustment is the basis of image edge extraction and image segmentation. By adjusting image gray histogram, the color difference between target area and background area can be enhanced. Consequently target features can be enhanced, and background features can be suppressed. This study tested the decorrstretch (de-correlation stretching), adapthisteq (finite contrast adaptive histogram equalization), histeq (histogram equalization), imadjust, stretchilm, Appendix A and imcontrast (calling contrast adjustment tool) functions which were used to adjust image contrast. Finally, the imcontrast function was used to adjust the image contrast, which can use an image contrast adjustment dialog box to realize the real-time observation adjustment effect and directly extract the optimal adjustment results.

Image noise reduction
Image noise can cause image blurring, pitting, etc., which will directly affect the image binarization results and bring errors to quantitative analysis of images. In this study, the effect of noise on quantitative analysis is reduced by image noise reduction operations and morphological operations after image segmentation. This study tested and compared medfilt2 two-dimensional median filtering, ordfilt two-dimensional sorting statistical filtering, wiener2 two-dimensional Wiener filtering, filter2 mean filtering, DTC discrete cosine variation, deconvblind blind deconvolution operation, a total of six methods about noise reduction. In order to preserve the image details as much as possible during noise reduction, it was finally determined to use the filter2 mean filtering method (average mean filter) to reduce image noise. The noise reduction operation will cause tailing particles area to be blurred. Therefore, during denoising SEM images of different quality backfill, the parameters should be carefully selected.
Q2-(Reviewer1): In the abstract, authors have mentioned the OTSU method. In which part of the research did authors use this method? I could only notice that the authors have used the boxcounting method.
Response 2: the section 3.4 SEM image segmentation uses this method. But there is a mistake of translation. I translated the proper noun "OTSU" to the maximum inter-class variance method in the text. This mistake has been revised in the manuscript.
In section 1 Introduction: The images were processed and the fractal dimensions of SEM images of the microscopic porous structure were calculated using OTSU and box dimension methods.
In section 3.3.2 Grayscale binarization: OTSU is an adaptive method for determining the image segmentation threshold. In MATLAB, OTSU can be called by the function to calculate the image segmentation threshold. The tailing samples used in the study were obtained from the Gaofeng mine in Guangxi province, China. The collected samples were divided into two types, i.e., Tailings A and Tailings B. Tailings A is produced by an old-fashioned beneficiation process and Tailings B is produced by a new type of beneficiation in a tin ore. The siliceous limestone was obtained from the quarry around the Gaofeng mine. In this experiment, the samples of mine waste siliceous limestone were ground in a horizontal ball mill with a volume of 35L, whereas the cylinder's rotational speed was 150 r/min. The processing time was 20 minutes. The limestone was made into stone powder having a certain particle size range, which was used to replace part of the cement. The basic physical properties of stone powder and tailings are shown in table 1. P42.5 cement with the strength grade of C30, produced by Changsha Xinxing Cement Factory, was selected as the cementing material. The main elements of the experimental raw materials were analyzed using the Dutch PANalytical X-ray fluorescence r, and the results are presented in table 2. Additionally, Mastersizer2000 was used to analyze the particle size of the raw materials, and the results are shown in figure 1. The SEM images of stone powder and tailings are shown in figure 2.  The introduction part is very short and needs to be extended. Despite the presence of very few studies that discuss such materials and even the techniques that were used in this research, authors need to explain more about other materials that were used to enhance the performance of cement. Following papers could help: -A novel approach of introducing crystalline protection material and curing agent in fresh concrete for enhancing hydrophobicity.
-Development of hydrophobic concrete by adding dual-crystalline admixture at mixing stage.
-Influence of early water exposure on modified cementitious coating.
Response 4: The introduction part has been extended. In this part other materials that were used to enhance the performance of cement are introduced. The revised introduction and literatures are as follows: In order to reduce the cost of cement in concrete and to manufacture special cement for various special purposes, many worldwide scholars have conducted extensive work on cement substitute materials and concrete additives. Siddique [1] studied effects of volcanic ash on consistency, setting times, workability, compressive strength, electrical resistivity of cement paste and mortar. Weerdt et al. [2] found that the presence of 5% of limestone in concrete led to an increase of the volume of the hydrates, as visible in the increase in chemical shrinkage, and an increase in compressive strength. Kupwade-Patil et al. [3] investigated the effectiveness of the use of volcanic ash along with silica fume as a partial replacement for Portland cement. Celik et al. [4] reported the composition and properties of highly flowable self-consolidating concrete mixtures made of high proportions of cement replacement materials such as fly ash and pulverized limestone instead of high dosage. Al-Kheetan et al. [5][6][7] introduced crystalline material along with a curing compound in fresh concrete to protect and extend its service life and developed hydrophobic concrete by adding dual-crystalline admixture during the mixing stage. However, there are a few materials used in mines backfilling and the research on these materials is limited. Hu et al. [8] assessed stone powder as a replacement of cement in cemented paste backfill (CPB), and studied strength characteristics and reaction mechanism. The results showed that strength of the backfill greatly reduced at an early stage, and slightly reduced in the final stages, while transscale characteristics between pore structure and macroparameters are still needed to be studied.