Use of Potabilized Water Sludge in the Production of Low-Energy Blended Calcium Sulfoaluminate Cements
Round 1
Reviewer 1 Report
This paper investigated the possibility of using thermally treated WPSs (TTWPSs) as SCMs in CSA-blended cement.
The research is well organized. However, I am a critic of this paper. The author explained CSA-blended cements have some benefits such as low carbon, energy saving, reduction of cost. However, in the research, I cannot find such benefits. Therefore, the following comments should be considered before published.
- Abstract is not well organized, so the reviewer recommend that follow that pattern [background] -> [objective] -> [process] -> [results] -> [contribution]
- In conclusion, the author explained that the CSA cements the following advantages, such as reducing carbon emissions, energy savings and reducing costs. However, In Results and discussion, I cannot find benefits. The author has to prove the benefits in the following ways. First the life cycle assessment or CO2 should be conducted. Second, the energy consumption should be compared to that of the OPC. Third, the net present value, the IRR or the savings-to-investment ratio should be completed. The author should be regarded as such an analysis to prove the benefit of the CSA.
- In References, The authors should include more references recently published in the Applied Science at least 5.
Author Response
Dear Reviewer,
we sincerely appreciate the insightful comments and suggestions given. The manuscript has been revised carefully according to these comments. Below, we address the questions raised in a point-by-point format. Thank you again for your work.
Sincerely,
The authors
This paper investigated the possibility of using thermally treated WPSs (TTWPSs) as SCMs in CSA-blended cement. The research is well organized. However, I am a critic of this paper. The author explained CSA-blended cements have some benefits such as low carbon, energy saving, reduction of cost. However, in the research, I cannot find such benefits. Therefore, the following comments should be considered before published.
1. Abstract is not well organized, so the reviewer recommend that follow that pattern [background] -> [objective] -> [process] -> [results] -> [contribution]
Response
Thank you so much for your comments. The abstract has been organized according the suggestions of the Reviewer.
2. In conclusion, the author explained that the CSA cements the following advantages, such as reducing carbon emissions, energy savings and reducing costs. However, In Results and discussion, I cannot find benefits. The author has to prove the benefits in the following ways. First the life cycle assessment or CO2 should be conducted. Second, the energy consumption should be compared to that of the OPC. Third, the net present value, the IRR or the savings-to-investment ratio should be completed. The author should be regarded as such an analysis to prove the benefit of the CSA.
Response
Thank you for the requests. More detailed information and further benefits, regarding CO2 and energy consumption as well as the comparison with OPC, have been included. They are reported in a separate paragraph entitled “Environmental implications of manufacturing CSA-based cements: kiln thermal requirements and CO2emissions”.
However, net present value, IRR or savings-to investment ratios are elements to be considered in a separate study, inasmuch as these were not the objective of this paper which is mainly focused on the technical validation and the environmental impact of CSA binders blended with a waste-materials (i.e. water potabilization sludges).
3. In References, the authors should include more references recently published in the Applied Science at least 5.
Response
Six references published in Applied Science are now present in the manuscript.
Reviewer 2 Report
This investigation reports the use of treated thermally water potabilization sludges (at 700°) as supplementary cementitious materials (SCM) in calcium sulfoaluminate cements (CSA). A neat CSA paste/mortar and two blends (20 and 35% cement replacement) were prepared and their main cementitious properties were measured : i) compressive strength development, ii) shrinkage/expansion; iii) thermal-thermogravimetric; iv X-ray powder diffraction, and v) mercury intrusion porosimetry.
The scope of the work is well planned a fits within the scope of the journal. However, a number of points (major and minor) should be addressed before I can recommend publication of the work.
- The w/b (or w/c) ratio(s) employed in this investigation is/are not mentioned at all in the manuscript. It is imperative to clarify this as all properties depend (a lot) upon the value(s) of this ratio. This is even more important for CSA binders.
- To my analysis, the authors have 16 self-citations out of 52 or 31%. This is well above the average about 15-20%. Hence, I suggest to replace some of the self-citations by well-established works. I will not give any suggestion as I do not want to bias, and furthermore, reviewer suggestion to cite his/her papers and acquaintance works is a poorer practice.
- The English has to be deeply improved. There are many poor expressions even in the abstract "... This article discusses the use of water potabilization sludges (WPSs) were employed as..."
- Spite the written introduction where the role of calcite/limestone as SCM is very much highlighted, limestone was not added (which is known to help in a synergistic way). Why limestone has not been added? I will strongly advise to add another sample/blend: 20% replacement with 15% of added limestone and to carry out a similar characterization.
- The paste elaboration (mixing procedure, etc.) is not reported at all. Some details would be very helpful.
- If the flexural strength values are available, they should also be reported. Interesting findings can be extracted from the flexural/compressive ratios.
- For the textural characterization, only Blaine values are provided. It is imperative to provide also the particle size distribution curves from laser diffraction. The reactivity strongly depends upon this.
- I would advise to report the thermal data up to the highest recorded temperatures (even if the authors very elusively stated "...No significant exo-/endo-thermal effects were found above 500°C..."). Weigh losses should be reported at higher temperatures.
- I suggest to replace CSH by C-S-H by obvious reasons.
- I suggest to analyze the powder patterns by the Rietveld method and to report/display the phase content evolution with time.
- Fig. 6. In my opinion it more informative to give these results as total porosity fraction (instead of cumulative Hg volume). Please redraw the figure.
Author Response
Dear Reviewer,
we sincerely appreciate the insightful comments and suggestions given. The manuscript has been revised carefully according to these comments. Below, we address the questions raised in a point-by-point format. Thank you again for your work.
Sincerely,
The authors
This investigation reports the use of treated thermally water potabilization sludges (at 700°) as supplementary cementitious materials (SCM) in calcium sulfoaluminate cements (CSA). A neat CSA paste/mortar and two blends (20 and 35% cement replacement) were prepared and their main cementitious properties were measured: i) compressive strength development, ii) shrinkage/expansion; iii) thermal-thermogravimetric; iv X-ray powder diffraction, and v) mercury intrusion porosimetry. The scope of the work is well planned a fits within the scope of the journal. However, a number of points (major and minor) should be addressed before I can recommend publication of the work.
Response
The authors express their gratitude to the reviewer for the comment.
1. The w/b (or w/c) ratio(s) employed in this investigation is/are not mentioned at all in the manuscript. It is imperative to clarify this as all properties depend (a lot) upon the value(s) of this ratio. This is even more important for CSA binders.
Response
Thank you for pointing out. The w/b ratios have been reported in the manuscript.
2. To my analysis, the authors have 16 self-citations out of 52 or 31%. This is well above the average about 15-20%. Hence, I suggest to replace some of the self-citations by well-established works. I will not give any suggestion as I do not want to bias, and furthermore, reviewer suggestion to cite his/her papers and acquaintance works is a poorer practice.
Response
Thank you for pointing out. The number of total references has been increased; we have added additional references related to the use of other supplementary cementitious materials and references dealing with kiln thermal energy requirement and CO2 emissions reports in the new paragraph entitled “Environmental implications of manufacturing CSA-based cements: kiln thermal requirements and CO2 emissions”.
Moreover, we also reduced the number of self-citations (now the percentage of self-citations is 17.5%).
3. The English has to be deeply improved. There are many poor expressions even in the abstract "... This article discusses the use of water potabilization sludges (WPSs) were employed as..."
Response
The manuscript has, once again, been reviewed by a mother tongue and typing errors have been eradicated.
4. Spite the written introduction where the role of calcite/limestone as SCM is very much highlighted, limestone was not added (which is known to help in a synergistic way). Why limestone has not been added? I will strongly advise to add another sample/blend: 20% replacement with 15% of added limestone and to carry out a similar characterization.
Response
The authors added by mistake almost only references (4 out of 5) dealing with the use of limestone as SMC for blended CSA cements. We have added additional references related to the use of other supplementary cementitious materials.
The aim of this manuscript was to evaluate the possibility of using a thermally treated waste material, often landfilled, as active supplementary cementitious materials. However, as suggested by the Reviewer, future studies dealing with the addition of another sample blend (e.g 20% replacement with 15% added limestone) will carried out in a similar experimental activity.
5. The paste elaboration (mixing procedure, etc.) is not reported at all. Some details would be very helpful.
Response
According to the suggestions of the Reviewer, more details about the paste elaboration have been added to the manuscript.
6. If the flexural strength values are available, they should also be reported. Interesting findings can be extracted from the flexural/compressive ratios.
Response
Unfortunately, flexural strength values are not available. Samples mortars were broken using a suitable mean able to avoid harmful stresses to the prisms before the compressive strength test (according to EN 196-1).
7. For the textural characterization, only Blaine values are provided. It is imperative to provide also the particle size distribution curves from laser diffraction. The reactivity strongly depends upon this.
Response
Particle size distribution data, obtained from laser diffraction, have been included in the text.
8. I would advise to report the thermal data up to the highest recorded temperatures (even if the authors very elusively stated "...No significant exo-/endo-thermal effects were found above 500°C..."). Weigh losses should be reported at higher temperatures.
Response
As suggested by the Reviewer, the old DT-TG figures have been substituted with those reporting thermal data up to 1000°C and a few comments have been added to the manuscript.
9. I suggest to replace CSH by C-S-H by obvious reasons.
Response
Thank you for your advice. CSH has been replaced by C-S-H.
10. I suggest to analyze the powder patterns by the Rietveld method and to report/display the phase content evolution with time.
Response
According to the suggestions of the Reviewer, XRD patterns have been analyzed by the Rietveld method. So, the evolution of the hydration process, in terms of ettringite, ye’elimite and belite concentration at different hydration times, has been reported in the manuscript (Figure 6).
11. Fig. 6. In my opinion it more informative to give these results as total porosity fraction (instead of cumulative Hg volume). Please redraw the figure.
Response
Thank you for pointing out; as suggested, total porosity has been reported in a new figure (Figure 8).
Round 2
Reviewer 1 Report
1. The author revised the manuscript appropriately by reflecting reviewers comments, however, before publishing the 'Applied Science', a one issue should be handled.
2. In Conclusions, if the author cannot prove the economic benefit, the economic benefit should be deleted from the paper.
Author Response
Dear Reviewer,
we thank you for revising our paper one more time. According to your suggestions, the "economic benefits" have been deleted from the manuscript.
The authors
Reviewer 2 Report
The authors have appropriately addressed the questions/recommendations/comments. In some cases, the suggestions have not been followed but sound reasons are provided. Now, I can recommend acceptance as it is.
Author Response
Dear Reviewer,
we thank you for revising our paper one more time and for accepting it in the revised version.
The authors
