Utilization of Municipal Solid Waste Incineration Bottom Ash in Cement-Bound Mixtures

Round 1

Reviewer 1 Report

The topic of using solid waste in cement is relevant and interesting. However, the work requires serious improvement.

1. It is unclear what is wrong with the shape, font and design of the text. It clearly needs to be fixed.

2. Please describe in more detail “Natural weathering" (line 55). What is its mechanism. Describe the technique itself in more detail, not just its result.

3. I think that section 1 and section 2 should be combined. This is not a review, but an experimental work (article). I don't think article needs a separate paragraph about applying bottom ash.

4. I think the authors got too carried away with describing the applications of bottom ash in section 2. I recommend shortening this part, it is not a Review.

5. The introduction lacks a specific formulation of the actual problem, goals and objectives.

6. Section 4 Results and discussion represents the smallest part of the article, but should represent the largest. The data obtained has been too modestly analyzed. There is a lack of research on structural changes. What happens in the structure of the material under loads? What role does the composition play in these changes?

7. The authors promise SEM research, but in fact it is not in the results. It is in the methods, but there is no discussion.

8. The article needs a significant recomposition. It doesn't seem scientific right now. The results are poorly presented.

Author Response

We are very grateful for the review and comments sent, which we referred to in the text. Below we present the answer to the Reviewer's questions and comments. The final text will be sent after taking into account the comments of all reviewers.

The corrections in the manuscript are marked in red. Due to the significant reconstruction of the structure of the article, please read the entire manuscript.

Best regards,

Szymon Węgliński & Gabriel Martysz, Poznan University of Technology

1. It is unclear what is wrong with the shape, font and design of the text. It clearly needs to be fixed.

Ans1. In the manuscript provided to the websystem, the fonts and template are correct (downloaded file is correct).

2. Please describe in more detail “Natural weathering" (line 55). What is its mechanism. Describe the technique itself in more detail, not just its result.

Ans2. “Natural weathering" was described more preciously. Chemical details are not provided because the paper is not intended to describe chemical aspects, but only engineering ones for geotechnics and road constructions.

3. I think that section 1 and section 2 should be combined. This is not a review, but an experimental work (article). I don't think article needs a separate paragraph about applying bottom ash.

Ans3. Section 2 was shorted. Described only the most importatnt aspects.

4. I think the authors got too carried away with describing the applications of bottom ash in section 2. I recommend shortening this part, it is not a Review.

Ans4. Section 2 was shorted. Described only the most importatnt aspects.

5. The introduction lacks a specific formulation of the actual problem, goals and objectives.

Ans5. The research methodology, purpose, basis and assumptions of the research were supplemented in introduction section.

6. Section 4 Results and discussion represents the smallest part of the article, but should represent the largest. The data obtained has been too modestly analyzed. There is a lack of research on structural changes. What happens in the structure of the material under loads? What role does the composition play in these changes?

Ans6. The research did not consider structural changes inside the mixtures after hardening. The compressive strength and frost resistance of the samples were assessed. At the stage of supplementing the article, it is not possible to demonstrate changes in the structure of the materials. This may constitute the next research stage.

7. The authors promise SEM research, but in fact it is not in the results. It is in the methods, but there is no discussion.

Ans7. No detailed SEM tests were carried out, and only the chemical composition was determined using a TESCAN VEGA 3 scanning electron microscope with the Bruker EDX attachment for elemental analysis. The SEM test record was incorrectly specified. A brief analysis of the chemical composition has been added to the manuscript.

8. The article needs a significant recomposition. It doesn't seem scientific right now. The results are poorly presented.

Ans8. The structure of the paper has been improved. The theoretical and research parts were recomposed, emphasizing research part of work.

Reviewer 2 Report

Here are some comments about this work:

-Explain the acronyms when the term is used for the first time.

-Clarify the novelty of this work.... think about why it should be published in this journal.

-Are the results in Table 3 from the literature?

-Could you add stress-strain curves from the compression test? It would be useful for the reader.

-Improve the presentation of figures 2 and 4 (axes, scale, colors).

-Figure 3.... scale of the photos (identify what is important).

-A deeper explanation of the results is required... it gives the appearance of a technical report.

-What is the perspective of this research?

None

Author Response

We are very grateful for the review and comments sent, which we referred to in the text. Below we present the answer to the Reviewer's questions and comments. The final text will be sent after taking into account the comments of all reviewers.

The corrections in the manuscript are marked in red. Due to the significant reconstruction of the structure of the article, please read the entire manuscript.

Best regards,

Szymon Węgliński & Gabriel Martysz, Poznan University of Technology

-Explain the acronyms when the term is used for the first time.

Ans1. The acronyms were explained

-Clarify the novelty of this work.... think about why it should be published in this journal.

Ans 2. A novelty indicated during the research is the assessment of the use of a mixture resulting from the combination of two waste materials - fine sands 0/2 and IBA for use on layers bound with a binder in road construction. Such mixtures are not commonly used in Poland. Additionally, the frost resistance of the resulting composite was assessed and the minimum percentage of cement added was determined to guarantee the possibility of obtaining a layer that meets the requirements of technical standards. Road surfaces in Poland must meet frost resistance requirements due to the frequent occurrence of frost damage (floating). Our own research has shown that it is possible to use waste materials into full-value building materials, with benefits for environmental protection, including the reduction of natural resources.

-Are the results in Table 3 from the literature?

Ans3. The results included in table 3 are the results of own research conducted as part of the research experiment

-Could you add stress-strain curves from the compression test? It would be useful for the reader.

Ans4. The testing machine that was used to assess the compression force of the samples did not contain a module that recorded the unit increase in force and did not generate individual values read in time samples. We only have the results of the determinations - compressive force and compressive strength value.

-Improve the presentation of figures 2 and 4 (axes, scale, colors).

Ans. OK

-Figure 3.... scale of the photos (identify what is important).

Ans. OK

-A deeper explanation of the results is required... it gives the appearance of a technical report.

Ans. The scientific nature of the research was emphasized by presenting an analysis of the results.

-What is the perspective of this research?

Ans. The manuscript was supplemented with the purpose of the work, basis and scope of research.

Reviewer 3 Report

Dear Authors,

 1. What is the purpose of the research? The authors did not provide it anywhere.

2. What is the justification for dealing with the issue of using (in construction) slags and ashes from municipal waste incinerators, which was the subject of research several dozen years ago and the results resulted in implementation? The authors themselves have written extensively about it: „In many countries around the world, combustion products are reused in construction. IBA applications include [12]: · admixtures to cement – Italy, Japan, Spain, · concrete and construction materials – Belgium, China, Netherlands, Portugal, Spain, · embankments – Czech Republic, Norway, Spain, Sweden, United Kingdom, · road construction – China, Denmark, France, Germany, Poland, Spain, Sweden, United Kingdom. Especially in road construction, IBA can be used for the following layers as an important alternative allowing conservation of natural aggregates and other natural materials [12, 16]:…………………. · bituminous layers – added to bituminous mixtures used on local roads.”

The presented work does not contain any novelties, no scientific aspect has been demonstrated. Authors should be reminded that scientific works should be creative, not imitative. The work submitted for review is reproductive and is a reproduction of known information. It does not bring any new content.

3. The work contains many substantive errors (often at the level of basic knowledge).

4. The authors alternately use the abbreviations BA or IBA when referring to bottom ash. Please explain this.

 5. Chapter 1. Introduction

Quotes:

line 32 „IBA is a porous, greyish, and coarse gravel material containing primarily glass, ceramics, minerals, and ferrous and nonferrous materials, along with small amounts of unburned materials and organic carbon” is actually a repetition line 28-31: „..and bottom ash (BA), which accounts for 80-85% of all residues. IBA (Incineration Bottom Ash) contains inorganic matter (stone, ceramics, glass), ferrous and non-ferrous metals and small amounts of unburned organic matter (plastics, fibres, wood, etc.). There is no need to repeat this in consecutive sentences.

 Line 41: quote „…….(including heavy metals) accumulate in much more mobile forms, e.g. as chlorides and oxides.”

Comment: Please verify your knowledge and correct any mistakes. Heavy metal oxides are among the least mobile forms. In turn, heavy metal chlorides are very volatile forms at waste combustion temperatures, which is why they are mostly carried out of the combustion chamber and do not remain in the BA.

 Line 51: quote: „….infiltration of diluted (leached) compounds and elements, such as sulphates, chlorides, heavy metals,…”

Comment: Dear Authors, sulphates and chlorides are salts of metals, including heavy metals. The quoted fragment of the text shows that the leached heavy metals are in elemental forms. This is a cardinal mistake

Dear Authors, sulphates and chlorides are salts of metals, including heavy metals. The quoted fragment of the text shows that the leached heavy metals are in elemental forms. This is a cardinal mistake.

 6. Chapter 3.2. Mixture design and sample preparation

Table 4 present research results - leaching tests of MSWI bottom ash. There is no description anywhere of how the leaching tests of MSWI bottom ash were performed.

 7. Chapter 4. Results and discussion

The chapter only presents research results, completely omitting the scientific discussion. The chapter does not contain any scientific aspects. This is a typical research report, without scientific considerations. Such tests can (and are) performed by commercial laboratories, presenting the results without engaging in scientific considerations.

It should be noted that Sustainability journal is a scientific journal, therefore articles should be scientific in nature. Such tests can (and are) performed by commercial laboratories, presenting the results without engaging in scientific considerations.

It should be noted that Sustainability journal is a scientific journal, therefore articles should be scientific in nature.

 8. Chapter 5. Conclusions

The conclusions resulting from the use of bottom ash from municipal waste incinerators in cement-bound layers, presented in this chapter, were mentioned by the authors in previous chapters, as this is a known and researched topic. How can it be concluded that the research "on the application potential of recycled aggregate from municipal waste incineration, i.e. bottom ash” is any novelty, when these materials and technologies have been implemented for many years?

It would not even be possible to explain that this is why research is being carried out, because the physico-chemical properties of BAs vary depending on their origin (which is, of course, true). Approaching the problem this way, it should be stated that BA, which is the subject of the authors' research, will never be identical in composition and properties (even if it comes from the same MSW incinerator) when it is used industrially.

 Best regards,

Reviewer 

Author Response

We are very grateful for the review and comments sent, which we referred to in the text. Below we present the answer to the Reviewer's questions and comments. The final text will be sent after taking into account the comments of all reviewers.

The corrections in the manuscript are marked in red. Due to the significant reconstruction of the structure of the article, please read the entire manuscript.

Best regards,

Szymon Węgliński & Gabriel Martysz, Poznan University of Technology

1. What is the purpose of the research? The authors did not provide it anywhere.

Ans1. The manuscript was supplemented with the purpose of the work, basis and scope of research.

2. What is the justification for dealing with the issue of using (in construction) slags and ashes from municipal waste incinerators, which was the subject of research several dozen years ago and the results resulted in implementation? The authors themselves have written extensively about it: „In many countries around the world, combustion products are reused in construction. IBA applications include [12]: · admixtures to cement – Italy, Japan, Spain, · concrete and construction materials – Belgium, China, Netherlands, Portugal, Spain, · embankments – Czech Republic, Norway, Spain, Sweden, United Kingdom, · road construction – China, Denmark, France, Germany, Poland, Spain, Sweden, United Kingdom. Especially in road construction, IBA can be used for the following layers as an important alternative allowing conservation of natural aggregates and other natural materials [12, 16]:…………………. · bituminous layers – added to bituminous mixtures used on local roads.”

The presented work does not contain any novelties, no scientific aspect has been demonstrated. Authors should be reminded that scientific works should be creative, not imitative. The work submitted for review is reproductive and is a reproduction of known information. It does not bring any new content.

Ans 2. A novelty indicated during the research is the assessment of the use of a mixture resulting from the combination of two waste materials - fine sands 0/2 and IBA for use on layers bound with a binder in road construction. Such mixtures are not commonly used in Poland. Additionally, the frost resistance of the resulting composite was assessed and the minimum percentage of cement added was determined to guarantee the possibility of obtaining a layer that meets the requirements of technical standards. Road surfaces in Poland must meet frost resistance requirements due to the frequent occurrence of frost damage (floating). Our own research has shown that it is possible to use waste materials into full-value building materials, with benefits for environmental protection, including the reduction of natural resources.

3. The work contains many substantive errors (often at the level of basic knowledge).

Ans3. Some " substantive" errors have been eliminated. Please indicate which errors the Reviewer pointed out.

4. The authors alternately use the abbreviations BA or IBA when referring to bottom ash. Please explain this.

Ans4. In the text considers IBA aspects. The notation of BA is considered as short definition of IBA.

5. Chapter 1. Introduction

Quotes:

line 32 „IBA is a porous, greyish, and coarse gravel material containing primarily glass, ceramics, minerals, and ferrous and nonferrous materials, along with small amounts of unburned materials and organic carbon” is actually a repetition line 28-31: „..and bottom ash (BA), which accounts for 80-85% of all residues. IBA (Incineration Bottom Ash) contains inorganic matter (stone, ceramics, glass), ferrous and non-ferrous metals and small amounts of unburned organic matter (plastics, fibres, wood, etc.). There is no need to repeat this in consecutive sentences.

Ans. repetitions have been removed

 Line 41: quote „…….(including heavy metals) accumulate in much more mobile forms, e.g. as chlorides and oxides.”

Comment: Please verify your knowledge and correct any mistakes. Heavy metal oxides are among the least mobile forms. In turn, heavy metal chlorides are very volatile forms at waste combustion temperatures, which is why they are mostly carried out of the combustion chamber and do not remain in the BA.

Ans. information regarding chemical processes was presented on the basis of literature analysis and quoted from it. Perhaps there were problems while translating the texts. The authors of the manuscript are not chemists but people involved in road engineering. We are not able to verify the correctness of the reactions taking place in slags, but we only rely on the knowledge disseminated by other researchers. Incorrectly quoted fragments of the manuscript were removed.

 Line 51: quote: „….infiltration of diluted (leached) compounds and elements, such as sulphates, chlorides, heavy metals,…”

Comment: Dear Authors, sulphates and chlorides are salts of metals, including heavy metals. The quoted fragment of the text shows that the leached heavy metals are in elemental forms. This is a cardinal mistake

Ans. Unfortunately, there was a translation error at this point. We are aware that the substances released during  leaching and weathering are not single elements but chemical compounds, as indicated in the initial part of the Introduction chapter.

6. Chapter 3.2. Mixture design and sample preparation

Table 4 present research results - leaching tests of MSWI bottom ash. There is no description anywhere of how the leaching tests of MSWI bottom ash were performed.

Ans. The standards on the basis of which the tests were carried out and national regulations defining the limit values were specified (ministerial regulation)

7. Chapter 4. Results and discussion

The chapter only presents research results, completely omitting the scientific discussion. The chapter does not contain any scientific aspects. This is a typical research report, without scientific considerations. Such tests can (and are) performed by commercial laboratories, presenting the results without engaging in scientific considerations.

It should be noted that Sustainability journal is a scientific journal, therefore articles should be scientific in nature. Such tests can (and are) performed by commercial laboratories, presenting the results without engaging in scientific considerations.

It should be noted that Sustainability journal is a scientific journal, therefore articles should be scientific in nature.

Ans. The scientific nature of the research was emphasized by presenting an analysis of the results.

8. Chapter 5. Conclusions

The conclusions resulting from the use of bottom ash from municipal waste incinerators in cement-bound layers, presented in this chapter, were mentioned by the authors in previous chapters, as this is a known and researched topic. How can it be concluded that the research "on the application potential of recycled aggregate from municipal waste incineration, i.e. bottom ash” is any novelty, when these materials and technologies have been implemented for many years?

It would not even be possible to explain that this is why research is being carried out, because the physico-chemical properties of BAs vary depending on their origin (which is, of course, true). Approaching the problem this way, it should be stated that BA, which is the subject of the authors' research, will never be identical in composition and properties (even if it comes from the same MSW incinerator) when it is used industrially.

Ans. A novelty indicated during the research is the assessment of the use of a mixture resulting from the combination of two waste materials - fine sands 0/2 and IBA for use on layers bound with a binder in road construction. Such mixtures are not commonly used in Poland. We know that in Poland there are no large-scale studies on the use of IBA for road surfaces and this research was intended to be an initiative to expand the topic of using materials treated as waste in road construction.

Reviewer 4 Report

Please see the attachment.

Comments for author File: Comments.pdf

NA

Author Response

We are very grateful for the review and comments sent, which we referred to in the text. Below we present the answer to the Reviewer's questions and comments. The final text will be sent after taking into account the comments of all reviewers.

The corrections in the manuscript are marked in red. Due to the significant reconstruction of the structure of the article, please read the entire manuscript.

Best regards,

Szymon Węgliński & Gabriel Martysz, Poznan University of Technology

Additional problems have been identified as follows:

1. The widespread practice of incorporating fly ash into cement mixtures to enhance properties and harness environmental benefits has been extensively documented. However, the present manuscript investigates the fabrication process and properties of products when utilizing bottom ash (BA) instead of fly ash (FA) in cement mixtures. How does the fabrication of the product in this manuscript, using bottom ash (BA) instead of fly ash (FA), compare to those made with fly ash? The manuscript's uniqueness has not been adequately addressed.

Ans1. The research did not analyze mixtures made on the basis of Fly ashes

2. Line 27, “various” is not accurate, define the type of emissions.

Ans2. The types of emissions were declared.

3. The author outlined the composition of IBA in Lina 35-38; why opt to reiterate it in Table 1? What crucial information can the audience gather from Table 1?

Ans3. Table No. 1 shows the diversity of the share of individual chemical compounds in IBA tested in different countries. Results from the analysis of other researches indicate the variability of substances found in IBA.

4. Line 65, what is MSWI bottom ash? Lack definition.

Ans4. MSWIBA definitions have been supplemented as Municipal solid waste incineration bottom ash (title of table 1 and in Line #49)

5. References are required to substantiate the IBA applications in "admixtures to cement," "concrete and construction materials," "embankments," and "road construction." The absence of critical comments from the author, such as distinctions in cost and environmental impact among these applications, is notable.

Ans5. The application of IBA to individual layers in various countries is given in the literature [12] as indicated in the heading. The article is not a review, but a research paper, therefore no more references were added. The possibilities of using IBA are generally listed, with specific references only in the field of road construction - the main topic discussed in the manuscript by the authors.

We have added our own assessment of the benefits of using IBA material.

6. Lines 82-157 exhibit poor structural organization. While the section is titled "BA application," the author delves into a multitude of policies and regulations starting from Line 93 and extensive surveys of MSW and incinerations from Line 112. How do these elements contribute to Section 2, "BA application"? Shouldn't they be considered background information instead?

Ans6. The structure and the content of chapters 1 and 2 has been reorganized.

7. The author opts to present points of view from others in Lines 84-92 but refrains from expressing agreement or disagreement. What is the author's stance on these viewpoints? Additionally, what are your own perspectives when considering the use of IBA in construction? What are the pros and cons from your point of view?

Ans.7 The content of the manuscript has been supplemented (in the conclusions chapter) with thoughts and comments regarding lines 84-92

8. Once again, regarding Table 2, Figure 2, and Figure 3, the author includes extensive information in the text without providing explanations or discussions. If the author assumes that the audience can extract all details directly from the graphs or tables, then presenting this information in the main context seems unnecessary and could be optionally placed in the supplementary information section.

Ans8. The structure and the content of chapters 1 and 2 has been reorganized.

9. In Line 178, the author mentions using SEM to detect the chemical composition, which lacks scientific soundness. SEM, in itself, does not directly detect chemical elements. However, it can offer valuable insights into the elemental composition of a sample when integrated with techniques like EDS or WDS. It is assumed that the author used EDS or WDS integrated with SEM, but clarification on this point is necessary.

Ans9. No detailed SEM tests were carried out, and only the chemical composition was determined using a TESCAN VEGA 3 scanning electron microscope with the Bruker EDX attachment for elemental analysis. The SEM test record was incorrectly specified.

10. Figure 4, the SEM images should be updated with high-resolution versions, as the current ones lack clarity. The scale bar is barely visible, and the plots also require higher resolution, particularly for the axis titles to be legible.

Ans.10. The figures in manuscript were modified.

11. The structure of Lines 184 to 187 is poor, and these pieces of background information should be relocated to the introduction section for better organization.

Ans11. The section were modified.

12. In Line 198, there seems to be a discrepancy regarding the difference between the "30BA/70_S" and "60BA/40_S" samples, considering the statements in section 3.2 that indicate they have the same composition. Clarification is needed to reconcile this apparent inconsistency.

Ans12. The research results were analyzed and described in more detail

13. Again, Figure 5 should go to support information section.

Ans13. Figure 5 is connected with research method and test. We do not understand why it should go to support section…

14. Line 225, lack of definition of “compressive strength index”

Ans14. The definition was supplemented

15. In Section 4.2, the statement that "the greater the amount of ash in the mixture, the more favorable the comparative index" lacks scientific soundness. It is essential to explain how IBA increases strength and capacity and elucidate the underlying mechanisms. Table 6 shows minimal differences in compressive strength between "60_BA/40_S/5C" and "45_BA/55_S/5C," considering the small difference or relatively high error. For instance, in the "RS_5C" case, minimal differences are observed. In "RS_7C," the compressive strength of "45_BA/55_S/5C" is close to "60_BA/40_S/5C," considering the variance. To support the statement, it is recommended to include more intermittent samples between the 60% BA and 30% BA compositions.

Ans15. The analysis of the results were supported.

16. For Figures 6-8, it is requested to align the axis bounds for all three plots. Inconsistencies in the y-axis bounds can be confusing for readers trying to compare strengths based on bar lengths. Ensuring consistency in the axis bounds will enhance the clarity of the visual comparison.

Ans16. Figures 6-8 were aligned

Round 2

Reviewer 1 Report

I recommend to transfer section 2 to section 1 or to obtain section 1 with subsections. Such an outstanding part of review is not needed in the Article (not a Review).

I recommend to transfer Table 3, Fig. 2 and Fig. 3 from Material and method section. This content is about results (Of course it is important description of material, but it looks strange in section 3)

Please, describe step by step all the method used in the article in separate subsections (X-ray spectroscopy line, SEM and EDX and others)

Author Response

Dear reviewer,

Thank you for the acceptance of the amendments to the manuscript. The current content is the result of the valuable comments of all reviewers.

R1:

I recommend to transfer section 2 to section 1 or to obtain section 1 with subsections. Such an outstanding part of review is not needed in the Article (not a Review).

Ans1: Due to the opinion of other reviewers, chapter 2 was left in the proposed form, however, table 1 prepared on the basis of the literature review was removed from paragraph 2, and several fragments that may have been redundant were also removed.

R2:

I recommend to transfer Table 3, Fig. 2 and Fig. 3 from Material and method section. This content is about results (Of course it is important description of material, but it looks strange in section 3)

Ans2: Table 3 and Fig 2 are included in the results section. Fig. 3 remained in the Material section due to the IBA illustration (without a broad description of the research).

R3:

Please, describe step by step all the method used in the article in separate subsections (X-ray spectroscopy line, SEM and EDX and others)

Ans3: Due to the lack of comments from other reviewers, in order not to expand the descriptive part, we did not characterize all research methods, but we briefly presented the assumptions of SEM/EDX spectroscopy

Best Regards,

Szymon Węgliński and Gabriel Martysz

Reviewer 2 Report

The comments and suggestions were fully addressed.

Author Response

Dear Reviewer,

Thank you for the acceptance of the amendments to the manuscript. The current content is the result of the valuable comments of all reviewers.

Best Regards,

Szymon Węgliński and Gabriel Martysz

Reviewer 3 Report

Dear Authors,

I would like to thank the authors for making additions and corrections. The quality of the manuscript has improved. It is true that the scientific discussion could still be worked on, but since (unfortunately) works without substantive scientific discussion are being published more and more often, in this case I accept the authors' work in the corrected version.

Dear Authors, please remember that the discussion of the results is not only about concluding that some parameter of the product's properties increases or decreases (due to, e.g., a change in the quantitative composition), but also about explaining why it happens.

I also draw attention to the authors that if information is provided that is incorrect, citing literature, this error should be commented on. Otherwise, an error is made which must be considered the authors' own error.

The authors' arguments cannot be accepted in terms of novelty either.

Advice for the future: please do not uncritically accept everything that is published. Please find your own way in research, do not duplicate what has been the subject of research for years.

Best regards,

Reviewer

Author Response

Dear reviewer,

Thank you for the acceptance of the amendments to the manuscript. The current content is the result of the valuable comments of all reviewers.

We will more work on research so that it can be better planned and have a more thorough analysis of the results obtained.

Best Regards,

Szymon Węgliński and Gabriel Martysz

Reviewer 4 Report

N/A

Author Response

Dear reviewer,

Thank you for the acceptance of the amendments to the manuscript. The current content is the result of the valuable comments of all reviewers.

Best Regards,

Szymon Węgliński and Gabriel Martysz