Study on the Performance Optimization of Plant-Growing Ecological Concrete
Round 1
Reviewer 1 Report (New Reviewer)
Comments and Suggestions for AuthorsThe manuscript “Study on Performance Optimization of Plant-Growing Ecological Concrete” contains several inaccuracies that require clarification and correction. The authors should write what they were guided by when selecting the three-parameter concrete test. This requires explanation.
General remarks
1. In the manuscript, the authors should explain what they were guided by when selecting the three levels of water to binder ratio, fly ash content and designed porosity.
2. Explain how the samples were adapted for compressive strength testing. If the test is to be representative, the surfaces of the tested samples should be adjusted accordingly. Otherwise, comparing the compressive strength of samples is impossible due to too large statistical dispersion of the tested parameter.
3. The authors should provide how many samples were tested for each of the 15 concrete mixtures. What was the SD and COV for each type of concrete specimens.
4. On what basis was the percentage porosity obtained by dividing the mass difference (before and after immersion) by the sample volume. This absolutely needs to be clarified. Eq.1. Why wasn't another method used to measure porosity?
5. The authors should write in the manuscript what Fig. 3 and Fig. 4 refer to.
Specific remarks
6. 46 line: What does "...concrete has good permeability and air permeability" mean?
7. 99 line: You should write: The composition of acetic acid is presented in table 5.
8. 121 line: It should read, for example, "Experimental research".
9. 173 line: explain how dimensionless quantities are obtained; in relation to what size.
10. 175-181 lines: The pH value test should be described correctly in style.
11. 206 line, Tab.7: It should be "Test value" instead of "Actual value".
I recommend an in-depth review of the manuscript, including comments, to make it an article suitable for publication in the Sustainability.
In its current state, the article should not be published.
Comments on the Quality of English LanguageModerate editing of English language required.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report (New Reviewer)
Comments and Suggestions for AuthorsJournal: SUSTAINABILITY (MDPI) ISSN 2071-1050
Manuscript ID: sustainability-3001324
"Study on Performance Optimization of Plant-Growing Ecologi-2 cal Concrete"
The article contains information regarding the analysis of properties of eco-friendly concrete, such as compressive strength, porosity, pH value, and the influence of acetic acid on concrete. The article requires clarification on several issues:
11. Please provide the number of samples tested in each series.
22. An important characteristic of the tested concretes is their water permeability. How do the authors intend to determine the rate of water flow, and particularly whether water flow will occur when voids are filled after some time?
33. The research focuses on short-term results, and the lack of data on long-term effects may limit their practical value. The studies should also include an assessment of the long-term durability of eco-friendly concrete under real operating conditions. This should consider potential changes in the concrete structure and its mechanical properties over time, as well as the effects of biological factors on its durability. Please explain this aspect.
44. Research on reducing the carbon footprint of concrete can lead to the development of more environmentally friendly production methods, including the use of alternative raw materials, more efficient cement firing processes, and the application of more energy-efficient technologies. Given the low strength of concrete, doubts about its durability in the context of damage by plant roots should address the eco-friendliness of concrete and its life cycle, conservation considering the possibility of recycling.
55. It is important for the research to encompass a wide range of factors that may affect the long-term durability of eco-friendly concrete. This should include not only its mechanical strength and resistance to atmospheric factors but also the impact of biological factors, such as plants, on its structure. The studies should consider diverse operating conditions to provide a comprehensive assessment of concrete durability.
66. It is necessary to conduct strength tests that consider the specificity of eco-friendly concrete and its reaction to environmental conditions. In the case of eco-friendly concrete, the research should also consider its resistance to biological corrosion and erosion, which may be caused by plants and water.
77. Research on eco-friendly concrete should be comprehensive and consider various factors that may affect its long-term durability. Special attention should be paid to the concrete's reaction to plant action and erosion to assess the potential risk of structural damage to this type of concrete.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report (New Reviewer)
Comments and Suggestions for AuthorsReview Study on Performance Optimization of Plant-Growing Ecological Concrete
Introduction, In the first paragraph, references 1 and 2 are irrelevant. Papers of Ido sella and Shimrit Perkol-Finkel R.I.P. are not cited (see Ido research page https://www.researchgate.net/profile/Ido-Sella ). You didn’t define what you mean by “Ecological concrete”. The relevancy of references 3-5 depends on the definition.
The second paragraph has the same problem. Ecological concrete has not been defined. As far as I am concerned, it does not have to be porous. Porous concrete is only one method of making concrete ecological in certain contexts. After you define the ecological concrete you may define a specific kind of ecological concrete for water permeability and plantability. That should be in the first paragraph.
A reference to experimental work is needed for the sentence “…pore water environment at an appropriate pH level.” In line 71. Even though one may think that concrete toxicity arises from its high pH, the toxicological test in which I was involved, showed no importance at all for the pore solution pH. The surface pH of the concrete decreases very fast in real life.
Table 2. You got the cement specific-gravity in the place of the fly-ash fineness, and the wrong units for fineness.
Table 4. Of which material is the composition? What are the units? Is it legal to add gypsum to concrete in China?
Lines 112-113, “…thus precisely and effectively predict in various indicators…” Well, only basic knowledge of statistics is needed to know that this is not true. First, any number without its accuracy is meaningless. Second, one cannot hide from the overfitting resulting from the ratio between the number of degrees of freedom in the model and the number of measurements. References 25-26 are not publications regarding the methods but examples of use. Please supply a reference to the method.
Table 6. I prefer the variables' name instead of A, B, and C
Continuous porosity needs clarification. Is V the cube volume, or is volume calculated by the weight difference out of the water and submerged in the water?
pH values that have been measured are not pore solution pH, and that should be stated clearly. The method which had been use measure mostly the diluted pH of soluble solids in the cement paste. It is more related to the buffering pH of the paste solids than to the pore solution pH.
What is the justification for using a second-order polynomial model? For example, for compressive strength, R2 for simple multivariant linear regression is 0.952 and the p-value is 8.31e-09.
Equations 2-4, like Table 6. It will be much more readable if the terms are related to the physical or chemical properties they are symbolising.
Using the same data which have been used to calibrate the model for testing it is a malpractice. The validation of the model should be performed with data that have not been used for its calibration. You could omit every time one data line and use it for validation 17 times.
Please specify in the methods the procedure for mixing acetic acid in the concrete. Why did you choose acetic acid which creates a soluble calcium acetate? You could use oxalic acid to receive an insoluble salt.
Line 262, for this work acetic acid was selected. The article does not select.
Subsection 5.1 –
The discussion is mostly speculative. The model has no scientific justification, only a statistical one. Since you selected a second-degree polynomial model, you may get an up-and-down behavior, and this is only in a very small range. Your interpretation may be right, but you have no way to prove it. Since it is highly speculative, you must bring references, to support your interpretation. For example, other references which demonstrate an optimum w/b around 0.3. reference for alkalinity reduction by fly ash, and so on… (you did so, excluding the mechanism of the acid as an activator, in subsection 5.2. so add some references also here and for the mechanism of acid activation).
Overall, this is an important paper that should be published once the flaws will be corrected.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report (New Reviewer)
Comments and Suggestions for AuthorsCompared to the previous version of the article, they have introduced corrections that largely take into account the reviewer's suggestions. However, there are still serious inaccuracies that require necessary correction.
Ad. 3 The article should explain the adjustment of the pressure surface of the samples in such a way that the compressive strength test is representative.
Comments on the Quality of English LanguageMinor editing of English language required.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report (New Reviewer)
Comments and Suggestions for AuthorsDear Authors,
I accept the corrections made.
Author Response
Dear Review Expert,
Here is the system requirement for the second round of revisions provided for your response. This round of modifications does not involve corrections to your content, so I apologize for having to trouble you with this matter.
Best regards.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe paper is about the investigation of performance of different mixes of cement-based composites for plant growing.
The state-of-the-art should be improved, adding comments and references about the significance of this type of concrete, with respect to other possible ecological solutions for concrete structures (e.g. other types of binder and material enhancement).
The style of the paper should be improved: in some parts it seems a laboratory report rather than a scientific paper. Methods and results should be presented with a critical approach, and more comments are needed.
Please describe better the numerosity of the samples, and describe better the methods. Not all the evaluated features are well defined.
Some comments are not convincing and not so scientific.
Conclusions are too generic. The aim of the research, the original contribution and the objectives are not clear. Not defined in the comments and conclusions the significance of the model.
Further recommendations are reported in the attached file.
Comments for author File: Comments.pdf
English should be improved.
Author Response
Dear reviewer,
Thank you very much for taking the time to review my manuscript. The following is my revision of your comments. I merged some of the same problems and modifications, so some of the changes are not shown below.
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Comments 1: The problem of introduction. |
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Response 1: I rewrote the introduction about pervious concrete, and corrected the part which is not detailed. this change can be found – line 25-50. |
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Comments 2: Epress in decimals. |
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Response 2: I modified the way of expression. this change can be found – line 102. |
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Comments 3: How was it adopted? |
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Response 3: The multiplication of this 1 and Rvoid has no practical significance, just to indicate the change from a percentage to a decimal. I am not good to modify the requirements of the specification, so I did not change this formula. |
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Comments 4: Not adequately defined. Standards? |
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Response 4: This change can be found – line 149-151, 173. |
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Comments 5: How were they evaluated? Not clear from the formula. (line 183-185) |
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Response 5: I rewrote the introduction of the response surface design method. This change can be found – line 122-133. If the detailed calculation process is written out, it is very cumbersome and verbose. In fact, these regression equations can be calculated by regression analysis software. We only need to analyze and optimize them. |
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Comments 6: Very complex and unclear, and not replicable. (line 187-200) |
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Response 6: It is necessary to analyze the significance of each item of the polynomial, and modify the formula through analysis, which is also the basis of image analysis later. For the deletion of non-significant items, unnecessary interference conditions can be effectively reduced. |
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Comments 7: How was it evaluated? How many samples? (table 5) |
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Response 7: These variance analysis indicators are calculated based on the previous 17 sets of tests, and the calculation can be completed by regression analysis software. |
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Comments 8: How is the compactness (or the presence of voids) impactant for the material performance? Why there are no fine aggregates? (line 232-239) |
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Response 8: The existence of voids is deliberate. In the previous calculation of mix design, we effectively reduce the amount of cementitious materials by designing the porosity index, so that it cannot fill the pores between aggregates. This is because the plant-growing eco-concrete needs to leave enough voids to accommodate the plant roots. The addition of fine aggregate can significantly improve the compressive strength, but it will lead to a serious decrease in porosity, which is inconsistent with our original intention, so no fine aggregate is added. |
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Comments 9: Why this choice of variables considered in the graphs? Not well explained in the text. Please justify the repetition of variables for the axes. The same for figures 2,3 and 4. |
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Response 9: Through the above analysis, we remove the influence of insignificant factors, which can be seen in the formula (line 201-203). For example, for R1, it only has two interaction factors, AB and BC, so we can only choose AB ( A and B as the coordinate axes respectively ) and BC ( B and C as the coordinate axes respectively ) for analysis. In fact, we will find that R3 can not be analyzed because there is no interaction term, but for the sake of research, we still carry out its interaction analysis discussion ( without abandoning the non-significant term ). |
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Comments 10: Not reliable: for low w/c ratios there is higher porosity. Please define better what do you intend with porosity and effective porosity. |
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Response 10: I am very sorry, I did not explain the meaning of effective porosity clearly in the text. This change can be found – line 153-157. Effective pores = all pores-invalid pores. Although the lower water-binder ratio reduces the amount of all pores, the increase of invalid pores increases the effective pores. |
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Comments 11: The problem of conclusions. |
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Response 11: I rewrote the conclusions, this change can be found – line 337-356. |
Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe paper concerns the subject of so-called plant-growing ecological concrete. The manuscript presents original research results and a modeling presented in the graphical form of the regression function describing relation between the composition of tested composites (water/binder ratio and range of the substitution binder with fly ash) and their selected technical properties (compressive strength, porosity and the pH). The presented model enabled the authors to indicate the composition that was optimal considering the selected criteria.
The manuscript appear to be interesting, however it requires major corrections and explanations. Parts of the manuscript may not be clear to the reader and should be improved or developed. Therefore, the manuscript in its current form does not appear to be suitable for publication. Some remarks (including editorial notes) are listed below.
Remarks/notes:
1) The title of the publication as well as the abstract section are adequate to the content. However it would be better to focus on the regression function instead of the “response surface” that is only the graphical presentation of the function and is not needed to indicate the optimal solution (it can be simply calculated without making any surface graph).
2) First of all the explanation what is the plant-growing concrete (lines 33-37) is not sufficient and is limited to only superficial information about the aggregate. It has not been explained what the composition of this unusual composite is (especially in the context of its name), its potential purpose, or expectations in terms of the level of characteristics. The reviewer requests that this topic be developed in the "Introduction" section, along with appropriate references to the literature.
3) Please provide the numbers of the standards of which criteria are met by the used materials listed in section 2.1. The reviewer expects that these are foreign local standards, which do not necessarily have to coincide with European or American standards and are not commonly known.
4) Please do not provide the commercial name of the admixture (or other components) unless there is a special reason to do so. Please explain what chemical compound the admixture is based on and what is its function, because the phrase "permeable concrete enhance" (line 80) is not informative. Was it a sealing admixture or a superplasticizer ensuring significant water reduction and lowering the water/cement ratio?
5) Please clarify what the phrase "in a quantity equivalent to 1/30 of the mass of cementitious materials " (line 81) means? 1/30 by mass or by volume of pure cement? It is customary in cement composite technology to express the amount of admixture as a mass percentage of the total mass of cement.
6) Is Table 1 summarizing the results of authors own tests? Giving the technical properties you need to give the source of the data, unless these were your own test results. Please add the source of the producer data sheet data in the reference or the testing method you have used.
7) Please use reasonable precision depending on the individual property. If, for example, the density is expressed in kg per 1 m3, there is no point in expressing the value with an accuracy of two decimal places (e.g. Table 1: apparent density 2592.69 kg/m3 = 2.59269 g/cm3 is an absurd precision in the case of building materials).
The same remark concerns Table 2 with the mass compositions of tested composites.
8) Please remove the text covering lines 84-96.
The calculation showing that the cement was replaced with fly ash by volume is too obvious and the entire fragment on this subject (including formulas No. 0, 2, 3, 4, which were numbered incorrectly in any case) is unnecessary and adds nothing to the paper. It was enough to provide information that the cement substitution was carried out in a given volume range and by volume.
9) Please remove the text covering lines 98-103. The entire fragment explains nothing particular to the paper.
10) Please give the source (references) of the Box-Behnken statistical design and explain the concept of statistical planning of the experiment – i.e. the relationship between input and output data, the reason for picking up the particular material variable, the type of optimization function used (what degree polynomial and why?), satisfactory intervals (why such?), level of significance, etc.
This part of the manuscript in its current form is not clear to people not involved in the experimental design of the experiment area.
11) Test of the so-called “porosity” (lines 123-134) has no sense. How can we talk about porosity testing when the specimen was not dried to a constant mass in an heater/oven, but left for 24 hours in "natural placement"? Please explain what is this "natural placement"? Were these room conditions, laboratory conditions, external environment?
According to what standard method was this study conducted to? The reviewer is afraid that the results absolutely do not indicate a property such as porosity as it compares the density of the specimen in a state of some temporary (unknown) humidity to the specimen in a state of total saturation with water. To determine porosity, you should compare the last one to a specimen dried to a constant mass in an oven, i.e. measure the mass loss for several consecutive days until it stabilizes.
12) What was the method of measuring pH? Have you used an automatic pH-meter (which one) or was it determined, e.g. by using acid titration and determining the specific content of hydrogen and hydroxide ions and calculating?
13) Please always write the units after spaces: e.g. "150 mm" instead of "150mm" (line 116) - please check the manuscript in this respect and correct it.
14) Results given in Table 3 are lacking information how many specimens were tested to determine the mean value, as well as SD (statistical deviation) and CV (coefficient of variation) that would show basic information on the homogeneity of the tested materials and repeatability, including the statistical significance of the results obtained. Please provide those data. If the SD/CV for the particular case are too high, such result shouldn’t be compared to the modelled predicted values.
15) The list of references is poor - only 20 items, including 3 titles of standards/technical specifications. Please do a better research on the literature on the topic.
16) The section "Conclusions" is a general summary rather than the actual conclusions of the manuscript. A scientific paper is not a report summarizing the results or observed trends, but primarily an attempt to conduct an analysis of the modeled phenomena. And this is missing in the manuscript, especially since the subject of the study is a new, little-known composite.
Regarding the content of the manuscript, investigation and modelling showed in the paper is interesting, however the manuscript need to be improved before publication.
Comments on the Quality of English LanguagePlease make a revision and correction of technical vocabulary and adjust it to the generally accepted and used in English, like use “cement paste” instead of colloquial “cement slurry” (line 47) and “slurry with cementation” (line 131) or “bulk density in the loose/compacted state” instead of “Packing density” or “Compact packing density” (Table 1), etc.
The reviewer recommends to ask professional to check the whole manuscript in terms of technical vocabulary.
Author Response
Dear reviewer,
Thank you very much for taking the time to review my manuscript. The following is my revision of your comments. My replies have been marked red.
1) The title of the publication as well as the abstract section are adequate to the content. However it would be better to focus on the regression function instead of the “response surface” that is only the graphical presentation of the function and is not needed to indicate the optimal solution (it can be simply calculated without making any surface graph).
Added the description of the regression equation. This change can be found – line 122-133.
2) First of all the explanation what is the plant-growing concrete (lines 33-37) is not sufficient and is limited to only superficial information about the aggregate. It has not been explained what the composition of this unusual composite is (especially in the context of its name), its potential purpose, or expectations in terms of the level of characteristics. The reviewer requests that this topic be developed in the "Introduction" section, along with appropriate references to the literature.
I rewrote the introduction about pervious concrete, and corrected the part which is not detailed. This change can be found – line 25-50.
3) Please provide the numbers of the standards of which criteria are met by the used materials listed in section 2.1. The reviewer expects that these are foreign local standards, which do not necessarily have to coincide with European or American standards and are not commonly known.
Attached the material requirements of the reference specification. This change can be found – line 104-105.
4) Please do not provide the commercial name of the admixture (or other components) unless there is a special reason to do so. Please explain what chemical compound the admixture is based on and what is its function, because the phrase "permeable concrete enhance" (line 80) is not informative. Was it a sealing admixture or a superplasticizer ensuring significant water reduction and lowering the water/cement ratio?
A reinforcing agent for pervious concrete is adopted. The reinforcing agent comprises the following components: nano-sized silicon powder, water reducing agent, cellulose, calcium sulfate whisker, trisodium phosphate, calcium carboxylate, alkali metal carbonate and formamide. The reinforcing agent can increase the bonding force of cement, improve the compressive strength and service life of permeable concrete pavement. The quality of the use of reinforcing agent is 3.3% of the quality of cementitious mate-rials.
5) Please clarify what the phrase "in a quantity equivalent to 1/30 of the mass of cementitious materials " (line 81) means? 1/30 by mass or by volume of pure cement? It is customary in cement composite technology to express the amount of admixture as a mass percentage of the total mass of cement.
This change can be found – line 102-103.
6) Is Table 1 summarizing the results of authors own tests? Giving the technical properties you need to give the source of the data, unless these were your own test results. Please add the source of the producer data sheet data in the reference or the testing method you have used.
These data are the results of my tests and also refer to the specification attached to the previous question.
7) Please use reasonable precision depending on the individual property. If, for example, the density is expressed in kg per 1 m3, there is no point in expressing the value with an accuracy of two decimal places (e.g. Table 1: apparent density 2592.69 kg/m3 = 2.59269 g/cm3 is an absurd precision in the case of building materials).The same remark concerns Table 2 with the mass compositions of tested composites.
The above content has been modified.
8) Please remove the text covering lines 84-96.
The calculation showing that the cement was replaced with fly ash by volume is too obvious and the entire fragment on this subject (including formulas No. 0, 2, 3, 4, which were numbered incorrectly in any case) is unnecessary and adds nothing to the paper. It was enough to provide information that the cement substitution was carried out in a given volume range and by volume.
The mix design of plant-growing ecological concrete is very different from the conventional concrete. The attached formula can help readers understand the subsequent content, which is also the reason why I attach Table 1. Pervious concrete can be simply understood as an aggregate accumulation formed by the bonding of cementitious materials. The calculation of mix proportion is based on the bulk density in the compacted state, and the amount of material is changed by adjusting the design porosity and water-binder ratio, which affects its performance.
9) Please remove the text covering lines 98-103. The entire fragment explains nothing particular to the paper.
The above content has been modified.
10) Please give the source (references) of the Box-Behnken statistical design and explain the concept of statistical planning of the experiment – i.e. the relationship between input and output data, the reason for picking up the particular material variable, the type of optimization function used (what degree polynomial and why?), satisfactory intervals (why such?), level of significance, etc.
This part of the manuscript in its current form is not clear to people not involved in the experimental design of the experiment area.
This change can be found – line 122-133.
11) Test of the so-called “porosity” (lines 123-134) has no sense. How can we talk about porosity testing when the specimen was not dried to a constant mass in an heater/oven, but left for 24 hours in "natural placement"? Please explain what is this "natural placement"? Were these room conditions, laboratory conditions, external environment? According to what standard method was this study conducted to? The reviewer is afraid that the results absolutely do not indicate a property such as porosity as it compares the density of the specimen in a state of some temporary (unknown) humidity to the specimen in a state of total saturation with water. To determine porosity, you should compare the last one to a specimen dried to a constant mass in an oven, i.e. measure the mass loss for several consecutive days until it stabilizes.
I am sorry that I did not explain this. This change can be found – line 153-168.
After the plant-growing ecological concrete specimen is completely immersed in water, the pores that can be filled with water are called effective pores, and the pores that cannot be filled with water are called invalid pores.
The purpose of the test is to determine the effective pore ratio in concrete that can be penetrated by plant roots. If the specimen is subjected to conventional drying treatment, the water in the invalid pores will be greatly lost, and the cementitious material is too dry, resulting in an increase in the water absorption rate of the concrete, thereby measuring the wrong effective porosity. Therefore, the natural placement treatment is adopted, and the treated specimen is required to not drip water, so as to ensure that the water evaporated from the specimen mainly comes from the effective pores and reduce the error.
12) What was the method of measuring pH? Have you used an automatic pH-meter (which one) or was it determined, e.g. by using acid titration and determining the specific content of hydrogen and hydroxide ions and calculating?
There is a serious lack of norms on how to deal with concrete in alkaline testing. I used the method most people use to test.
For the pH test, I used the alkalinity meter used in the electrode method, which is calibrated with a buffer and can display the reading directly without the need for calculation.
This change can be found – line 173-174.
13) Please always write the units after spaces: e.g. "150 mm" instead of "150mm" (line 116) - please check the manuscript in this respect and correct it.
The above content has been modified.
14) Results given in Table 3 are lacking information how many specimens were tested to determine the mean value, as well as SD (statistical deviation) and CV (coefficient of variation) that would show basic information on the homogeneity of the tested materials and repeatability, including the statistical significance of the results obtained. Please provide those data. If the SD/CV for the particular case are too high, such result shouldn’t be compared to the modelled predicted values.
I used three sample data to average according to the specification requirements. (line 178).
The statistical analysis indicators of these samples are shown in Table 5.
15) The list of references is poor - only 20 items, including 3 titles of standards/technical specifications. Please do a better research on the literature on the topic.
Added the corresponding specifications and references of the papers.
16) The section "Conclusions" is a general summary rather than the actual conclusions of the manuscript. A scientific paper is not a report summarizing the results or observed trends, but primarily an attempt to conduct an analysis of the modeled phenomena. And this is missing in the manuscript, especially since the subject of the study is a new, little-known composite.
I rewrote the conclusion, this change can be found – line 336-356.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors did not adequately respond to the reviewer's recommendations. The paper has not been enhanced in significance, and the results not enough discussed. Conclusions are too generic.
Comments on the Quality of English LanguageEnglish has been improved.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe feature measured in the research is not porosity (regardless of whether the authors add the term "effectiv" or not). Porosity is the content of pores in the structure of the material and not the ability to absorb water by the material in an air-dry state before testing.
