Use of Computed Tomography Scan Technology to Explore the Porosity of Concrete: Scientific Possibilities and Technological Limitations
Round 1
Reviewer 1 Report
- Line 187, how was the upper gray threshold of 5500 selected to define pores?
- The manuscript did not include any experimental work to verify the CT results. The authors need to explain how the results were confirmed.
Author Response
Thank you very much for your comments.
Reviewer 2 Report
The article summarizes several possibilities for quantitative evaluation of the individual properties and spatial and morphometric characteristics of pores present in the material of concrete based on tomographically obtained data. Although tomographic data acquisition technology does not provide sufficient resolution yet and only macro-pores can be evaluated in this way, provided approaches can also be used to evaluate other objects, such as fibers, cracks, aggregates etc. and I find the described options attractive. I would recommend a minor revision:
r. 30: Consider using the word technique instead of technology.
r. 42-44: “The scan measures the initial and final intensity of all the X-rays, thus finally determining the density at all points of the specimen.”
I think this sentence can be misleading. Industrial tomographs cannot normally monitor the initial and final intensities (or all parameters needed) to such an extent that the density of individual volume elements of the matter can be determined. Please omit the sentence, or provide a more detailed explanation or reference regarding the initial intensity measurement and tomographic densitometry.
r. 73: Provide a direct reference to IUPAC (e.g. https://doi.org/10.1351/goldbook)
r. 95-98: Pros and cons are not divided into these two sentences. Consider this form: They can only provide the pore-size distribution, but neither their spatial distribution nor their morphological parameters. Moreover, the information that they provide is related to the open porosity and not to the close one, which is more interesting when studying this phenomenon.
r. 148: Can you provide more information about the CT data acquisition and reconstruction in this section? What was the geometry of the irradiation - cone beam, spiral...? Have been all specimens tomographically scanned together or one after each other? Did you use both X-ray tubes mentioned or just one? What were the radiation parameters? What detector did you use? Did you use a filtered back projection algorithm for reconstruction or any other method? Was it necessary to handle any artifacts (e.g. beam hardening or scattering from wires)?
r. 151: It should be emphasized that the “resolution” here has the meaning of the voxel dimensions. Otherwise, it can be understood as the dimensions of the smallest distinguishable particle.
r. 164-179: Consider move the text above 146 for better information flow.
r. 180-182: Consider move the text above 133 for better information flow.
r. 188: On what basis the threshold value was determined? Is it based on some algorithm, knowledge of the overall porosity of the used material or the visual assessment of the image data? When the specimens were scanned one after each other, have you take into account e.g. variation in radiation intensity? Are the intensity values in all six reconstructed volumes exactly the same for the same material phases? Can you discuss the accuracy of pore segmentation?
r. 236: I recommend merging the information from Figure 6, 7 and 8 into one graph.
r. 271: I recommend merging the information from Figure 10, 11 and 12 into one graph.
r. 304: I recommend merging the information from Figure 13, 14 and 15 into one graph.
r. 381: I recommend using only one of Figures 17 or 18.
r. 367: Have you tested any mechanical parameters of used specimens after the tomography? If so, adding values of these parameters, e.g. compressive strength, to the Table 2 would be very interesting.
r. 614: I recommend considering reducing the number of self-citations.
Results: Please consider the need of using intervals in graphs where it is not necessary due to sorting the results.
Author Response
Thank you very much for your comments. The corrections are marked in blue in the paper.
Author Response File: 
Author Response.pdf
Reviewer 3 Report
Very interesting work in general,. in my opinion. Please see some comments and suggestions below.
- fig 1. this figure itself does not show much. any topic will have increased publications during the last years as the number of published papers increases in all fields together with the number of publishers and journals. maybe this diagram should be normalized with something like the number of papers in concrete or similar. this would give more reasonable results for a comparison. if the purpose is not to show the growth in the topics but rather compare the topics with each other then it is OK, I think
- fig 2. add "dimensions in mm" to the figure
- section 2. you say that the 6 specimens were taken from a bigger 150x150x600 piece but you do not mention anything about the properties of this concrete and how it was made. some details need to be added so as to understand what it is about. I see that you mention these details later, but something also need to be said in the beginning.
- is the resolution of 30x30x30 micro meters enough for this type of investigation? are there limitations because of this resolution? what could be achieved if better resolution could- be obtained? please comment on these
- why don't you start with checking standard concrete (instead of fiber reinforced concrete) with this procedure? I understand that one would need to start with simpler models rather than starting with a more complex model so I wonder why this investigation is not made in the simplest form of concrete, to be able to see how it behaves and what kind of results it can give.
- it would be interesting to compare your results about porosity with results obtained from determining porosity using another traditional method. have you done that? what could such a comparison reveal? do you think that your method is more accurate than traditional techniques? please comment on that
- please give us more details about the size of the equipment used and whether it is mobile or not. I am wondering if this equipment could be carried to the site to do in-situ testing of concrete elements, or if it needs to be in the lab checking only specimens of concrete. That is very interesting as I understand this technology could give valuable results for testing real concrete structures for cracks, etc.
- There are too many self-citations (at least 12 counted). Please try to limit the number.
Author Response
Thank you very much for your comments. The corrections are marked in red in the paper.
Author Response File: Author Response.pdf
