Using Recycled Material from the Paper Industry as a Backfill Material for Retaining Walls near Railway Lines

Round 1

Reviewer 1 Report

Review comments:

1. There are exact lines copied from manuscript text ( e.g., line 30) and pasted in the abstract. Please rewrite it as abstract is the true reflection of the paper and direct picking up line from text decreases the standard.

2. Authors should remain consistent with the tense (either present or past tense) throughout the paper. Specially check the Introduction section.

3. In line 48, what do you mean by presented. Is it the work presented by the authors or the text indicates about already established work by other authors?

4. In line 59, check the abbreviation. Is it RCA or RAC? The full form suggests RCA and not RAC

5. In line 51-52, the tense is not appropriate, rephrase the sentence.

6. The introduction section can benefit if the authors clearly defines the research question, literature review and summarisation of the work done. In current form all these appears to be mixed and hence is ambiguous. 

7. In methods, please explain how did the author chose the percentage composition of the composite mixtures to test in the laboratory. 

8. How is dry density represented (Check line 204)?

9. What is the symbol in line 241-242? Similarly, in line 280-281,  in line 319-320. Check other instances too.

10.  In the Conclusion section it is mentioned that the composite is impermeable layer. How does the author look into the groundwater recharge aspect? In terrains and hilly areas the level of ground water is very low and if further impermeable layer is promoted, how does the authors look into the augmention of the groundwater layer?

 

 

 

 

Author Response

Autor’s comment:

I apologize because there are no more visible corrections in the text of the reviewed article (file english-edited-25554 6 1 2021), but they were deleted during the English proofreading. However, I hope our answers are accurate and detailed enough.

1. There are exact lines copied from manuscript text ( e.g., line 30) and pasted in the abstract. Please rewrite it as abstract is the true reflection of the paper and direct picking up line from text decreases the standard.

Lines 9-20: we corrected the abstract and the rest part of the article where similar sentences were used.

OLD ABSTRACT:

Abstract: About half of natural – virgin material is consumed by construction industry, which also generates a large amount of waste material for landfills. On the other hand, globally 420 million tonnes of paper and paperboard are produced annually and the production is still growing. The production processes results in a significant waste generation and only in Europe 11 million tonnes of solid waste is generated per year as a result of production of almost 100 million tonnes of paper. The objective of this research is to develop a new geotechnical composite from residues of the deinking paper industry and to present its practical application, e.g.  as a back-fill material behind a retaining structure. After different mixtures were tested in a laboratory, the technology was validated by building a pilot retaining wall structure near a railway line. It was confirmed that the composite with 30 % of deinking sludge and 70 % of deinking sludge ash reaches high enough strength, but at the same time allows some deformations before the failure. The pilot retaining wall structure promotes the use of the recycled material in a sustainable design while adhering to the government legislative measures.

New Abstract:

The construction industry uses a large amount of natural virgin material for different geotechnical structures. In Europe alone, 11 million tonnes of solid waste is generated per year as a result of the production of almost 100 million tonnes of paper. The objective of this research is to develop a new geotechnical composite from residues of the deinking paper industry and to present its practical application, e.g., as a backfill material behind a retaining structure. After different mixtures were tested in a laboratory, the technology was validated by building a pilot retaining wall structure in a landslide region near a railway line. It was confirmed that a composite with 30% deinking sludge and 70% deinking sludge ash had high enough strength, but experienced some deformations before failure. Special attention was paid to the impact of transport, which, due to the time lag between the mixing and installation of the composite, significantly reduced its strength. The pilot retaining wall structure promotes the use of recycled materials with a sustainable design, while adhering to government-mandated measures.

 

Line  207: the sentence, used in the abstract, was changed.

2. Authors should remain consistent with the tense (either present or past tense) throughout the paper. Specially check the Introduction section.

The reviewed version of the paper was lectured by MDPI English editing service.

3. In line 48, what do you mean by presented. Is it the work presented by the authors or the text indicates about already established work by other authors?

In the line 41-42, this work is not presented by us, it is presented by other authors. We add this detail into the text.

4. In line 59, check the abbreviation. Is it RCA or RAC? The full form suggests RCA and not RA

Line 52: it was our typing mistake and we changed it.

5. In line 51-52, the tense is not appropriate, rephrase the sentence.

Line 45-47: the sentence was corrected in the past tense.

If paper sludge ash were to be used only as a binder in the construction industry, some problems due to the presence of lime would be observed, but it could be very useful for the stabilization for road structures or as a backfill material

6. The introduction section can benefit if the authors clearly defines the research question, literature review and summarisation of the work done. In current form all these appears to be mixed and hence is ambiguous. 

Line 22-98: the Introduction is shortened and simplified. Some details about the structure of different composited were omitted. We hope we wrote the chapter more clearly.

7. In methods, please explain how did the author chose the percentage composition of the composite mixtures to test in the laboratory. 

Lines 118-119: next text is added:

In order to design a backfill material for a retaining wall structure for the stabilization of a landslide near a railway line, several mixtures consisting of different ratios of DSA and DS were tested. Among them, two mixtures (Table 2) with sufficiently good geomechanical characteristics and suitable properties for compaction and installation were tested in the laboratory.

8. How is dry density represented (Check line 204)?

Line 117, 208, 262, 263, 300, 301: in the pdf document right symbols was automatically changes to different one. It was corrected to γ.

9. What is the symbol in line 241-242? Similarly, in line 280-281,  in line 319-320. Check other instances too.

Line 224, 225, 226, is symbol ε_A

262-263, 300-301 is γ_d,max

10. In the Conclusion section it is mentioned that the composite is impermeable layer. How does the author look into the groundwater recharge aspect? In terrains and hilly areas the level of ground water is very low and if further impermeable layer is promoted, how does the authors look into the augmention of the groundwater layer?

Lines 394-400: an explanation is added into the text:

As the area covered with such an impermeable layer is not very wide, the impact upon the groundwater recharge is limited. However, one should consider such structure as a ground water barrier which disturbs shallow ground water flows. Thus, the use of this kind of structure should combined with properly designed drainage system, which minimize the effect of ground water disturbance. In the case of retaining structure presented within this paper, vertical and horizontal drainages were employed to enable effective drainage of water behind the retaining structure. 

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript entitled „ Using recycled material from the paper industry for back-fill 2 material of the retaining wall near the railway line” aims to demonstrate the use of deinking paper industry residues as construction materials.

The English in the manuscript should be improved before publishing. The font in the manuscript is not uniform.

From my point of view, the paper is more technical paper than original scientific paper. I am missing some scientific contribution of this study. As from technical perspective, it has a particular contribution. The authors should pay a little more attention to the scientific approach of this important and relatively interesting topic.

For the improvement, please check the following comments:

 

Key words don’t say a lot about the topic presented in the manuscript, they are more general.

Line 35: the reference (Gang, 2008) should be stated in brackets

Line 40: not fibre recycling, but paper recycling

Lines 49-50: What about the raw materials used in paper production and its influence on paper sludge mineralogy?

Lines 48-116: You have given a lot of attention to the use of paper ash and paper slide in conduction. It is quite extensive and I am afraid readers might lose attention during reading like I did. Perhaps this section should be shortened a bit and you may put emphasis on concrete facts or even show it in a Table. Take that into account. Additionally, can paper ash and sludge be used for some other industries and which ones?

Lines 95-96: “The objective of this research is to develop a new geotechnical composite from the residue of a paper mill production…“ in the abstract and materials and methods is deinking sludge and ash, here is paper mill, in title paper industry. All the terms should be unique and specified for the material that is used for the research in the study.

Lines 132 and 143: Table 1 and 2. Are the results presented in the table your results? If yes, than these tables should be in result and discussion part, not in the materials and methods. Additionally, I am missing some discussion about the results in these tables. Why have you measured it, what are they saying about the DSA and DS? For example, why is CaO the component that is the most abundant in DSA and DS? Can the chemical composition of DSA and DS influence the properties of the produced material?

Lines 138, 143 (table 2) 204, 241, 242, 280, 281, 319, 320: there are some symbols in the brackets missing. Please check the pdf file.

Lines 157, 348, 386: The abbreviation for litres should be stated in SI unit as L not as l  and mg/L not mg/l

Lines 348 and 386: Table 6 and Table 8: Why were the listed metals and other components taken into consideration for concentration determination? Are they specific for the paper industry or is it determined by the legislation?

Author Response

Autor’s comment:

I apologize because there are no more visible corrections in the text of the reviewed article (file english-edited-25554 6 1 2021), but they were deleted during the English proofreading. However, I hope our answers are accurate and detailed enough.

The reviewed version of the paper was lectured by MDPI English editing service.

From my point of view, the paper is more technical paper than original scientific paper. I am missing some scientific contribution of this study. As from technical perspective, it has a particular contribution. The authors should pay a little more attention to the scientific approach of this important and relatively interesting topic.

We agree that the paper is a little bit more technical, but we think there are also some interesting scientific points in it:

Mixture of DSA and DS has not yet been tested in any laboratory as a back-fill material and used for the retaining wall structure. We add some explanations in the next lines:

• 11-13, 81-84, 363-364, 377-378

Additional contribution to the science is time behaviour of the material between mixing and installing. We add next explanation in lines: 85-90

None of the studies to date have dealt with changing the strength characteristics of a material during mixing and installation. Here, the time of transport of the material from the place of mixing to installation is crucial. In the study, we found that, over time, the strength properties decrease significantly, which may be crucial for the stability of the retaining wall. The study notes that the materials in the laboratory must also be tested in terms of installation time in order to provide the designer with relevant data regarding the geomechanical characteristics of the composite.

We add some explanations also in the next lines:

Lines 17-18, 246-248, 373-375,

For the improvement, please check the following comments:

 Key words don’t say a lot about the topic presented in the manuscript, they are more general.

Line 21: Key words were changed to:

paper sludge ash; deinking sludge; paper industry; back-fill material; retaining wall

Line 35: the reference (Gang, 2008) should be stated in brackets

Line 29: It is deleted

Line 40: not fibre recycling, but paper recycling

Line 34: It is changed to paper recycling

Lines 49-50: What about the raw materials used in paper production and its influence on paper sludge mineralogy?

Lines 43-44: We added some details into text:

The production process with different fillers, pigments, and coagulates influences the type of paper ash. Also, the technology and temperature in the boilers have an effect.

Lines 48-116: You have given a lot of attention to the use of paper ash and paper slide in conduction. It is quite extensive and I am afraid readers might lose attention during reading like I did. Perhaps this section should be shortened a bit and you may put emphasis on concrete facts or even show it in a Table. Take that into account. Additionally, can paper ash and sludge be used for some other industries and which ones?

Line 31-98: The Introduction was shortened and simplified. Some details about the mixture of different composites were omitted.

Paper ash and sludge could be used in:

• Mining industry as a back-fill material (Line 55)
• Cement industry, concrete manufacturing, brick industry (Lines 66,67)

Lines 95-96: “The objective of this research is to develop a new geotechnical composite from the residue of a paper mill production…“ in the abstract and materials and methods is deinking sludge and ash, here is paper mill, in title paper industry. All the terms should be unique and specified for the material that is used for the research in the study.

Line 35, 75, 405,407: we changed the term “paper mill” to the “paper industry”

Lines 132 and 143: Table 1 and 2. Are the results presented in the table your results? If yes, than these tables should be in result and discussion part, not in the materials and methods.

Results from those tables are from our study. They were moved to the chapter 3 Results and discussion (Line 196-212)

Additionally, I am missing some discussion about the results in these tables. Why have you measured it, what are they saying about the DSA and DS? For example, why is CaO the component that is the most abundant in DSA and DS? Can the chemical composition of DSA and DS influence the properties of the produced material?

Lines 199-200: an explanation was added for LOI. High values of LOI were due to high fibre or other organic compounds.

Lines 201, 203: Higher CaO content in DSA and DS was due to the use of fillers and coatings in the deinking process of the production of new paper from used paper. Also, higher CaO led to the higher pozzolanic reactivity of the composite made from DSA and DS

Lines 138, 143 (table 2) 204, 241, 242, 280, 281, 319, 320: there are some symbols in the brackets missing. Please check the pdf file.

Line 117, 208, 262, 263, 300, 301: in the pdf document some symbols was automatically changes to different ones. It was corrected to γ.

Line 224, 225, 226, is symbol ε_A

Lines 157, 348, 386: The abbreviation for litres should be stated in SI unit as L not as l  and mg/L not mg/l

Lines 126, 235, 361: it is changer to mg/L

Lines 348 and 386: Table 6 and Table 8: Why were the listed metals and other components taken into consideration for concentration determination? Are they specific for the paper industry or is it determined by the legislation?

Lines 325 Listed metals and other components are determined by Slovenian legislation. (UL RS, No. 10/14 date 22. 2. 2014); table 6 (Results from the leaching tests).  As I know it is quite similar to Spanish, Portuguese and Croatian legislation.

Lines 361: Listed metals and other components are also determined by Slovenian legislation UR RS No. 98/15;  table 7 (Results of the chemical analysis of the water from the drainage system)

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The author responed to all my questions.