Influence of Fibers and Curing Conditions on the Pore Morphology in Plain and Fiber-Reinforced High-Performance Concrete through the Use of Computed Tomography Scan Technology
and Riyadh Hindi 2Round 1
Reviewer 1 Report
This study relates to the evaluation of the porosity of concretes through CT-scan. This paper presents an experimental program, rich of tests and results.
However, authors should provide a line-numbering to to facilitate the work of reviewers.
Overall, there are too many graphs in this paper (26 graphs). You should try to remove some of them which are not essential or try to mix some of them. You should have less than 20 graphs in total.
In Introduction, paragraph 3 : "This work demonstrates..." It would be better to use "aims to demonstrates...". This is the introduction section, not the conclusion or abstract.
In Introduction, paragraph 3 : When citing [33-42], you should give a short analysis of these studies and not only cite them. There is not point to cite a lot of references with summarizing them. What is point, conclusions and outlooks of these previous studies. Then you should link these comments with your study.
Note that the same remark can be made when citing [7-11] in paragrah 1 in the introduction.
In 2.1. : Please give more details about the cement used : strength, Blaine fineness, setting time, etc.
In 2.1. : Why did you use nano-silica ? Did you have requirements on concrete performances ?
In page 6 : "It can be observed in Figures 2" : Figure 2.
In 3.1. : In the title, please correct "porosyt" by porosity.
In Fig. 6 : in Y-axis, please remove a zero in numbers to be consistent with others graphs. 0.40% --> 0.4%
In conclusions : please give some outlooks for your study.
Author Response
REVIEWER 1
This study relates to the evaluation of the porosity of concretes through CT-scan. This paper presents an experimental program, rich of tests and results.
However, authors should provide a line-numbering to facilitate the work of reviewers.
ANSWER: Done.
Overall, there are too many graphs in this paper (26 graphs). You should try to remove some of them which are not essential or try to mix some of them. You should have less than 20 graphs in total.
ANSWER: In the new version of this paper the graphs have been compacted. Now there are only 14 figures.
In Introduction, paragraph 3: "This work demonstrates..." It would be better to use "aims to demonstrates...". This is the introduction section, not the conclusion or abstract.
ANSWER: Done.
In Introduction, paragraph 3: When citing [33-42], you should give a short analysis of these studies and not only cite them. There is not point to cite a lot of references with summarizing them. What is point, conclusions and outlooks of these previous studies. Then you should link these comments with your study.
ANSWER: A brief comment about references 33-42 has been included in the new version of the paper.
Note that the same remark can be made when citing [4-11] in paragrah 1 in the introduction.
ANSWER: A brief comment about references 4-11 has been included in the new version of the paper.
In 2.1.: Please give more details about the cement used: strength, Blaine fineness, setting time, etc.
ANSWER: The cement used agrees with the European Standard EN 197-1:2011 “Cement. Composition, specifications and conformity criteria for common cements”. This reference has been included in the new version of the paper.
In 2.1. : Why did you use nano-silica? Did you have requirements on concrete performances?
ANSWER: We used nano-silica because we are interested in high-strength and low-porosity concrete, in order to show better the influence of the fibers and the curing conditions on the porosity.
In page 6: "It can be observed in Figures 2" : Figure 2.
ANSWER: Done.
In 3.1. : In the title, please correct "porosyt" by porosity.
ANSWER: Done.
In Fig. 6 : in Y-axis, please remove a zero in numbers to be consistent with others graphs. 0.40% --> 0.4%
ANSWER: Done.
In conclusions: please give some outlooks for your study.
ANSWER: In the new version of the paper, some outlooks of our study have been included.
Reviewer 2 Report
In my opinion, this research is very interesting, it provides very useful results about the effect of the addition of fibers to the internal porosity of high-strength concretes. Viewing the effect of the fibers from this perspective can help to understand the fracture behavior of this type of concretes. Although the paper is very well organized, with ideas and discussions well exposed, the following minor comments should be considered to improve the quality of the work.
SPECIFIC COMMENTS
Introduction
- This statement is not correct: “up to date the research conducted has assumed the hypothesis that, in general, the fibers do not modify the concrete matrix”. There are previous studies with X-ray CT on UHPFRC, in 2019, which confirm that the addition of steel fibers modify the matrix. This sentence should be changed and to add those references. (Authors can look for in Cement and Concrete Research, Materials and Design, etc.)
- Please clarify the acronym IUPAC.
- The introduction section little is said about the state of the art and it is not clear why this study is necessary. Approximately half of the introduction talks about what has been performed in this study. It is necessary to include a more extensive state of the art.
Experimental program
2.2 Materials
- English must be revised and corrected.
- British and American English is mixed in the text. (behaviour/behavior, fibre/fiber, to analyse/to analyze etc.).
- “50 mm high” must be changed by “50 mm height”.
- I don’t understand this sentence: “Six of them were poured with plain concrete”. Maybe the verb is not correct.
- In this sentence: “After curing process, the specimens were scanned using a CT scanner to investigate the concrete properties”.It is very general to use concrete properties, it is necessary to specify more (pore properties, pore structure, etc.).
- Figure 1. It has been published in other two previous papers. Figures must be original.
- Compressive strength results of all different mixtures and their standard deviation should be shown.
2.3 Scanning process
- It should be changed 25x25 μm2 by μm2.
- It should be changed “Figures 2” by “Figure 2”.
- It should be changed “These fact” by “These facts”.
- It should be changed “Not the whole specimen was studied” by “the whole specimen was not studied”.
- Please, it is necessary to mention which void size is considered by authors “difficult to be identified”. Specify numeric data.
- The authors should explain why larger pores are not taken into account when greater damage involves a less strength material. Therefore, a greater influence on the behavior of the material.
3.1 Total volume of voids and porosity
- It should be changed “Total volume of voids and porosyt” by “Total volume of voids and porosity”
- The standard deviation of average results should be shown in Table 2.
- The porosity values are underestimated due to the selection of strict range of grey scale. For this reason, the total porosity is so low. At least, this aspect should be mentioned.
- I don’t agree with this statement: “It is concluded that, in this case, steel fibres help to increase the internal porosity.”. There are recent studies, in 2019, which have shown the opposite effect in ultra-high-performance concretes. This might be because the amount of fibres is significantly higher. In my opinion, it should be mentioned that the addition of low amount of fibres increase the porosity, but no when are added in a high amount of fibres, as happened in UHPFRC [references].
- I think it is mixed NMPS and NMAS in the text. The text must be checked.
3.4 Variation of porosity and porosimetric curves along the depth
- It should be changed “Variation of to porosity and porosimetric curves along the depth” by “Variation of porosity and porosimetric curves along the depth”.
- The figures should be changed from black&white to color version, especially from figures 9 to 16, which are really difficult to see the curves.
3.6 Correlation between the pore orientation and the fiber orientation
- In my opinion, it should be changed “Correlation between the pore orientation and the fiber orientation” by “Correlation between the pore and the fiber orientation”.
Conclusions
The conclusion section is too extensive. It should be summarized, especially at the beginning, where a summary of the research is presented again. It is not necessary.
If the authors carry out all the proposed changes, my opinion is that the article could be publishable.
Author Response
REVIEWER 2
In my opinion, this research is very interesting, it provides very useful results about the effect of the addition of fibers to the internal porosity of high-strength concretes. Viewing the effect of the fibers from this perspective can help to understand the fracture behavior of this type of concretes. Although the paper is very well organized, with ideas and discussions well exposed, the following minor comments should be considered to improve the quality of the work.
SPECIFIC COMMENTS
Introduction
This statement is not correct: “up to date the research conducted has assumed the hypothesis that, in general, the fibers do not modify the concrete matrix”. There are previous studies with X-ray CT on UHPFRC, in 2019, which confirm that the addition of steel fibers modify the matrix. This sentence should be changed and to add those references. (Authors can look for in Cement and Concrete Research, Materials and Design, etc.).
ANSWER: In the new version of the paper this issue has been corrected and some references have been added.
Please clarify the acronym IUPAC.
ANSWER: Done
The introduction section little is said about the state of the art and it is not clear why this study is necessary. Approximately half of the introduction talks about what has been performed in this study. It is necessary to include a more extensive state of the art.
ANSWER: I consider that the length of the introduction is Ok. It is explained the uses and the advantages of fibers for concrete, and the state-of-the-art of computer tomography scan technology is included. The introduction is focused on the main topic of this paper, i.e., the use of computed tomography scan technology.
A sentence about the interest of this study has been included in the introduction.
Experimental program
2.2 Materials
English must be revised and corrected. British and American English is mixed in the text. (behaviour/behavior, fibre/fiber, to analyse/to analyze etc.).
ANSWER: Done
“50 mm high” must be changed by “50 mm height”.
ANSWER: Done
I don’t understand this sentence: “Six of them were poured with plain concrete”. Maybe the verb is not correct.
ANSWER: Corrected.
In this sentence: “After curing process, the specimens were scanned using a CT scanner to investigate the concrete properties”. It is very general to use concrete properties, it is necessary to specify more (pore properties, pore structure, etc.).
Figure 1. It has been published in other two previous papers. Figures must be original.
ANSWER: The research shown in this paper is an evolution of the one carried out by Minguez, Vicente and co-workers, of which I was part. In consequence, Figure 1 represents well the manufacturing process of the specimens. In the new version of the paper, Figure 1 includes the references.
Compressive strength results of all different mixtures and their standard deviation should be shown.
ANSWER: The average standard deviation of the mixtures have been included.
2.3 Scanning process
It should be changed 25x25 μm2 by μm2.
ANSWER: Done
It should be changed “Figures 2” by “Figure 2”.
ANSWER: Done
It should be changed “These fact” by “These facts”.
ANSWER: Done
It should be changed “Not the whole specimen was studied” by “the whole specimen was not studied”.
ANSWER: Done
Please, it is necessary to mention which void size is considered by authors “difficult to be identified”. Specify numeric data.
ANSWER: The paragraph has been rewritten, in order to clarify the idea.
The authors should explain why larger pores are not taken into account when greater damage involves a less strength material. Therefore, a greater influence on the behavior of the material.
ANSWER: The largest voids (greater than 10 mm length) have been discarded, since the number of voids greater than this value is really small (less than three voids per specimen) but they have a significant impact on porosity, etc.
3.1 Total volume of voids and porosity
It should be changed “Total volume of voids and porosyt” by “Total volume of voids and porosity”
ANSWER: Done.
The standard deviation of average results should be shown in Table 2.
ANSWER: Done.
The porosity values are underestimated due to the selection of strict range of grey scale. For this reason, the total porosity is so low. At least, this aspect should be mentioned.
ANSWER: Done.
I don’t agree with this statement: “It is concluded that, in this case, steel fibres help to increase the internal porosity.”. There are recent studies, in 2019, which have shown the opposite effect in ultra-high-performance concretes. This might be because the amount of fibres is significantly higher. In my opinion, it should be mentioned that the addition of low amount of fibres increase the porosity, but no when are added in a high amount of fibres, as happened in UHPFRC [references].
ANSWER: I think the sentence is Ok. In this particular case, with an amount of fiber of 7.8 kg/m3 and a compressive strength of around 70 MPa, it is observed that steel fibers help to increase the internal porosity. This is not an UHPC.
I think it is mixed NMPS and NMAS in the text. The text must be checked.
ANSWER: The paper defines the “nominal maximum pore size” NMPS, which is analogous to the well-known “nominal maximum aggregate size” o NMAS. In the rest of the paper, only the NMPS is mentioned.
3.4 Variation of porosity and porosimetric curves along the depth
It should be changed “Variation of to porosity and porosimetric curves along the depth” by “Variation of porosity and porosimetric curves along the depth”.
ANSWER: Done.
The figures should be changed from black&white to color version, especially from figures 9 to 16, which are really difficult to see the curves.
ANSWER: Done.
3.6 Correlation between the pore orientation and the fiber orientation
In my opinion, it should be changed “Correlation between the pore orientation and the fiber orientation” by “Correlation between the pore and the fiber orientation”.
ANSWER: Done.
Conclusions
The conclusion section is too extensive. It should be summarized, especially at the beginning, where a summary of the research is presented again. It is not necessary.
ANSWER: Done.
If the authors carry out all the proposed changes, my opinion is that the article could be publishable.
