The Workability and Crack Resistance of Natural and Recycled Aggregate Mortar Based on Expansion Agent through an Environmental Study
Round 1
Reviewer 1 Report
The paper describes the comparative results on the use of natural and recycled aggregates for the production of cement mortars. The manuscript is interesting because the recycling of building materials is a sustainability strategy towards which the construction sector should be directed. That is why the document is of high interest for the scientific field of building materials.
The manuscript is well structured and the results are well described. However, some minor changes need to be made. I am sending you a PDF with my suggestions included.
As a general comment, I recommend that you review the bibliography published by MI Sanchez Rojas and M. Frías , two senior researchers from the Materials Recycling Research Group of the Spanish National Research Council.
I also recommend that you rewrite the conclusions as indicated in the attached PDF.
Comments for author File: 
Comments.pdf
Author Response
Dear Editor,
Thank you for your notification, and really appreciate for two reviewers’ valuable comments and suggestions. Based on these comments and suggestions, all the revisions in the manuscript have been highlighted by ‘Track Changes’ in MS Word, which you recommended. Also, the revisions are detailed through point-to-point response to each comment.
Date: 2021. 1.3.
The responses to editor and two reviewers are listed as below:
â‘ Response to Reviewer #1:
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M1) I recommend you to check the bibliography of Frías, Moisés ; Sánchez de Rojas, María Isabel (Research Group on Recycling of Building Materials - CSIC Torroja) |
Answer:
The authors would like to thank the reviewer for this suggestion. The recommended scholars are awesome and the research group is out-standing. We have read some of their papers, all of which are fantastic and really impressive, and we are pretty sure that it will equip us with a deeper view into this research field.
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M2) Line 86, You should define what NA and RA means. I think you should write it in the figure caption. |
Answer:
The authors would like to thank the reviewer for his carefulness. According to the reviewer, it’s suggested to define NA and RA in the figure caption. Actually, the definition of NA and RA is presented in this paragraph. NA and RA in Fig. 1 have been defined in the figure caption.
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M3) Line 95, You must include the following data: - Water-cement ratio -Aggregate-cement relationship - Mixing procedure according to standards |
Answer:
Reviewer’s comment has been fully accepted. The supplement information has been added into the revised manuscript.
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M4) Line 95, Sample size |
Answer:
The authors would like to thank the reviewer for his carefulness. The sample size is presented in the next paragraph, and the sample size is 70.7mm × 70.7mm × 70.7mm.
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M5) It would be good if you could indicate the specific name of the machine used |
Answer:
The authors would like to thank the reviewer for his carefulness. The name of the machine has been added in this paragraph.
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M6) Line 120, You must indicate: - Data of the machine used - Sample preparation data |
Answer:
Reviewer’s comment has been fully accepted. In this part, the specimens were prepared and curing for 28 days before SEM and XRD tests.
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M7) Line 125~126, Is this decision based on literature? |
Answer:
The authors would like to thank the reviewer for his carefulness. This decision is not based on any specific reference, but CO2 emission calculation is one part in environmental evaluation.
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M8) Line 127~129, How do you quantify? What procedure do you use? |
Answer:
The authors would like to thank the reviewer for his carefulness. The procedure and the way to quantify the carbon emission have already been illustrated in this part, as shown in Fig. 3.
The environmental protection of recycled aggregate is supposed to be studied from CO2 emission. In this paper, the carbon emissions of NAM and RAM per unit of cement are calculated and compared. CO2 emission is calculated step by step from material demolition, process transportation and recycled aggregate production to quantify greenhouse gas CO2 pollution systematically. The CO2 emission system for the NAM and RAM production is depicted in Fig. 3.
Fig. 3. CO2 emission system for the NAM and RAM production.
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M9) Line 134, It would be interesting to include the RAM and NAM data in the same figure (NAM 7d and RAM 7d) and (NAM 28d and RAM 28d) in order to compare easily the result. |
Answer:
The authors would like to thank the reviewer for his carefulness. In order to depict the data more clearly. The figures in compressive test were divided into 4 individual figures. We have thought to combine these lines together, but it will be difficult to distinguish with each other.
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M10) Line 137, I don't understand the meaning of this sentence |
Answer:
The authors would like to thank the reviewer for his carefulness. This sentence has been modified as ‘the 7d compressive strength of mortar with 9% EXP content is the highest in all groups of specimens’.
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M11) Line 188, ¿La porosidad de la muestra influye en los resultados? You should measure the porosity. It is a very simple test that can help to understand your results |
Answer:
The authors would like to thank the reviewer for his carefulness. It’s a simple test, but we didn’t measure the porosity during the tests. So, we will take it into consideration in our further researches and analyze the results together.
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M12) Line 189, Why this conclusion? It may be that the RAM absorbs more water than NAM and reduces the mixing water. This generates more porosity in the samples |
Answer:
Reviewer’s comment has been fully accepted. And this part has been modified as below:
The bubbles on the surface of Nam specimens are obviously less than those of ram specimens, which is related to the particle size and fineness modulus of ram. Also, the RAM absorbs more water than NAM and reduces the mixing water, which generates more porosity in the samples.
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M13) Line 197, You must define the identified peaks |
Answer:
The authors would like to thank the reviewer for his carefulness. Actually, the peak in this figure is quartz, and it has been analyzed in this paragraph.
Figure 9 shows the XRD chemical composition pattern of RAM with 0% EXP, 9% EXP and 9% EXP. The strength of mortar and concrete is mainly from quartz. The quartz content of RAM is less than NAM, which is the main reason why the strength of RAM is lower than that of NAM.
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M14) You should mark in the figures the results that you explain in the text. |
Answer:
Reviewer’s comment has been fully accepted. The figure has been replaced as below:
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M15) L227-245 This text describes the procedure, not the results. It should be included in "methodology". |
Answer:
The authors would like to thank the reviewer for his carefulness. This part of procedure has been removed into Materials and Methods.
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M16) Line 229~230, Is this decision based on literature? |
Answer:
The authors would like to thank the reviewer for his carefulness. This decision is not based on any specific reference, because it’s common. In addition, a reference has been added at this part to enhance this decision.
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M17) How is the quality of the material defined? |
Answer:
The authors would like to thank the reviewer for his carefulness. As shown in Table 2, the quality of materials is defined by per ton in actual use. This is a macro calculation. The ‘Factor’ is the calculated I.
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M18) Line 240, Is this data based on literature? |
Answer:
The authors would like to thank the reviewer for his carefulness. The data is based on calculation and the reference is cited in this paper.
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M19) Line 240, Is I in formula 3? |
Answer:
The authors would like to thank the reviewer for his carefulness. The ‘Factor’ is the calculated I. Table 2 has been modified.
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M20) Line 242, Justify this decision. |
Answer:
The authors would like to thank the reviewer for his carefulness. In this part, other components like EXP is hard to calculating. So, we only take these 3 main components into consideration.
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M21) Line 258, You must rewrite the conclusions of the manuscript due to currently they are a summary of the results. Describe the conclusions based on the quantification of the results. |
Answer:
The authors would like to thank the reviewer for his carefulness. The conclusion has been modified as below:
In this paper, the aggregate is fine aggregate. The natural aggregate and recycled aggregate, combined with the utilization of expansion agent, are investigated and discussed based on mechanical performance, micro-mechanism and environmental evaluation. Various tests including compressive strength test, flexural strength test, XRD, SEM and CO2 emission evaluation are conducted. The conclusions are drawn as below:
- The compressive strength of NAM is higher than that of RAM, while the flexural strength of NAM is less than RAM. Further, the trend of mechanical strength is similar that it increases first and then decrease when the EXP proportion reaches the optimal. The strength value of recycled aggregate is acceptable compared with that of NAM.
- From the XRD and SEM patterns, the quartz is the source of strength in NAM and RAM. The ettringite occurs in the early stage of cement hydration and the C-S-H are the main courses of shrinkage- compensating mechanism. At the same time, the CaO and MgO may hydrated to Ca(OH)2 and Mg(OH)2, and the volume expand relatively. The effect of EXP on NAM and RAM is similar, and it expose significant influence.
- The proportion of Production and Transport of Cement occupies the most, around 94% to 96% of CO2emission. The CO2emission of RAM is a little bit less than NAM, as a result, the utilization of recycled aggregate from CDW or other environmental-friendly resources may reduce the energy consumption.
Reviewer 2 Report
The aim of this paper is of interest but authors should be improve some aspect:
Section 1. Introduction: Authors have made a brief review of the current state of the art by adding similar publications, but the conclusions they reached are missing. It would be advisable to considerably increase the number of references (40 is an acceptable number) and to include the most significant differences in their paper compared to other works.
Section 2. Material and Methods: Materials and Methods section is very complete. Perhaps, to improve it, it would be necessary to incorporate information on the standards of the tests carried out and to complement the information of the LCA by including the evaluation methodology used, the functional unit or, for example, commenting that a limit of the cradle-to-gate system has been followed, as they indicate when listing the stages of the process evaluated.
Section 3. Results and discussion: The authors should support the methodology used in section 3.3. on the assessment of the carbon footprint with other previous studies or, if it is new, justify its validity, for example through empirical methodologies. Similarly, it would be advisable for them to justify the origin of the data provided in Table 2.
Section 4. Conclusion: The conclusions are clear and concise, nothing to comment on.
It would be advisable to delve further into a novel aspect of the article such as cost reduction estimates.
References: I recommend to include more references.
Author Response
Dear Editor,
Thank you for your notification, and really appreciate for two reviewers’ valuable comments and suggestions. Based on these comments and suggestions, all the revisions in the manuscript have been highlighted by ‘Track Changes’ in MS Word, which you recommended. Also, the revisions are detailed through point-to-point response to each comment.
Response to Reviewer #2:
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M1) Section 1. Introduction: Authors have made a brief review of the current state of the art by adding similar publications, but the conclusions they reached are missing. It would be advisable to considerably increase the number of references (40 is an acceptable number) and to include the most significant differences in their paper compared to other works. |
Answer:
Reviewer’s comment has been fully accepted. The authors appreciated reviewer’s precision and carefulness very much. The references have been added.
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M2) Section 2. Material and Methods: Materials and Methods section is very complete. Perhaps, to improve it, it would be necessary to incorporate information on the standards of the tests carried out and to complement the information of the LCA by including the evaluation methodology used, the functional unit or, for example, commenting that a limit of the cradle-to-gate system has been followed, as they indicate when listing the stages of the process evaluated. |
Answer:
The authors would like to thank the reviewer for his carefulness. Section 2 has been modified and highlighted.
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M3) Section 3. Results and discussion: The authors should support the methodology used in section 3.3. on the assessment of the carbon footprint with other previous studies or, if it is new, justify its validity, for example through empirical methodologies. Similarly, it would be advisable for them to justify the origin of the data provided in Table 2. |
Answer:
Reviewer’s comment has been fully accepted. At this part, some references have been added.
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M4) Section 4. Conclusion: The conclusions are clear and concise, nothing to comment on. |
Answer:
The authors would like to thank the reviewer for his carefulness. Thank you for your comment.
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M5) It would be advisable to delve further into a novel aspect of the article such as cost reduction estimates. |
Answer:
The authors would like to thank the reviewer for his carefulness. Thank you for your comment. Cost reduction estimates is a good idea, and if possible we will discuss it in our further researches.
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M6) References: I recommend to include more references. |
Answer:
The authors would like to thank the reviewer for his carefulness. More references have been added.
