Effect of Superabsorbent Polymers on the Self-Healing Properties of Pre-Damaged Concrete

Round 1

Reviewer 1 Report

Dear authors,

The paper is aimed at investigating and summarizing the results of a wide campaign of the use of SAP on pre-cracked cement based matrix. The work covers experimental studies and tackles an important topic which falls within the topic of the MDPI.

The work is worth doing. However, there are a number of issues (not a conclusive list):

Figure 1 – Authors must increase the scale bar. Legend should also bee improved. Sugestion: Use A, B, C to better identify images.

 

Authors should inform SAP and SAND granulometric curves or D50. At table 3 authors indicate that SAP diameter range between 150 to 300 um. This information should be improved. I suggest also add average value and standard deviation

 

What is the moisture content of SAP ?

 

How the authors justify the use of vacuum to obtain the dry mass? The absorption at vacuum is higher in comparison to regular absorption test.

 

Since room-lab temperature and relative humidity interfere the results at Table 3 authors must inform these information’s.

 

Inform the methods of results presented at Table 3

 

Is table 2 information provided by company ?

 

At line 89 use sand-to-cement instead OPC-to-sand.

 

The different Water amounts presented in Table 4 is quite confusing. I suggest to improve this data presentation at table 4.

 

Improvements must be made at topic 2.3 and 2.4. Authors can not inform about pre-damaged specimens, informing compressive force, followed by topic 2.4 indicating a flexural strength.

 

Line 109 – 1kN.min-1 is not a loading speed. Who authors obtained the 70% peak force information?

 

Line 110 – ‘another part did nothing’ rewrite this sentence.

 

Line 115 – The mechanical methods is confusing. There is mixed information regarding compressive and flexural test. Create subtopics to facilitate the manuscript understanding.

 

Methods and results writing must be improved.

 

Is there another reference to support the Power’s model hypoteses? Otherwise will be quite complicated to explain the improvement observed at 0.35 samples.

 

Line 153 – the mentioned pores are not formed after matrix hardening.

 

Regarding Figure 2,3,4 and 5, standard deviation bars must be presented.

 

Figure 7 needs a scale (indicate if the presented surface is the sample sides, bottom or top surface.

 

SEM images must have a bigger scale. EDS methods are not presented at the manuscript. Please indicate the EDS points or indicate at methods if a EDS mapping was performed.

 

Figure 9 SEM images have a high quality. Other SEM images (e.g Figure 10) does not.

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The topic is good, but there are some major issues to consider.

1.      In the abstract, it should contain the aim/objective, methodology/experiments, findings, etc. Please rewrite the abstract.

2.      The introduction has no proper of focus, the novelty and knowledge gap of study are not known and the objective of the study is not stated.

3.      In the last paragraph of Introduction part, authors should justify their investigation. What can be done at the end of this study and what the results of this study provide for the literature?

4.      Figure 4 and 5 have low resolution, in general the resolution in all figures!

5.      The accuracy and reproducibility of the data should be presented more clearly

6.      SEM images must be discussed in details.

7.      Conclusion is not just about summarizing the key results of the study, it should highlight the insights and the applicability of your findings/results for further work, where is the recommendations for scientific community and possible using fields? Where those materials will be candidate for using...?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript presents an investigation on the self-healing performance of pre-damaged concrete with SAP. The results have interest, but the uncertainties associated with the experimental methods render the overall usefulness limited. Some grammatical errors are present throughout the manuscript and this needs revision. Also, interpretation of results was weak at times which has to be strengthened.

1. The literature review part of this paper was quite poor. There were many studies investigating the self-healing behavior of concrete with SAP, but the authors did not provide a comprehensive literature review. The authors should make a proper improvement in literature review section before claiming the novelty of this paper.

2. The specimens in this research were 40 by 40 by 160 mm prisms, they were not the proper size for ASTM C39 testing requirement.

3. The author should describe how the specimens split in two pieces, and then refer which standard to do the compression damaging for 40 by 40 by 80 mm prisms. The current description of the pre-damaging method was quite confused.

4. The samples should be well-polished before EDS quantitative analysis.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors handled the points well, which led to the improvement of the manuscript, and therefore I recommend the manuscript be accepted for publication.

Author Response

Thank you very much for your affirmation of our work.

Reviewer 3 Report

The present form of this manuscript can be published.