Review Reports

Round 1

Reviewer 1 Report

Manuscript: applsci-2266947

Journal: Applied Sciences.

Paper: “Analysis of the effect of capillary water absorption on the resistivity of cementitious materials".

 

1-   The originality and the scientific value of the topic are acceptable as it shows improving CWA of mortar using different percentages of cementitious materials.

2-   The abstract section gives the summary of the research work in a concise manner.

3-   I recommend the authors to further analyze the results of other similar research works which not discussed in the Introduction/literature review.

4-   The experimental methodology is very thorough and process of specimen’s preparation is clearly mentioned e.g. very clear figures. However, in Methodology section it’s not clear which type of curing has been used in specimens curing process and which standards have been complied with for compressive strength, CWA and resistivity experiments. Furthermore, more explanation needed in drying process (mass loss) of the specimens e.g. oven temperature.

5-   The presentation and clarity of results and data are good. However, the authors are kindly recommended to provide some further details/analysis about the rate of initial water absorption, which is referred as the water absorption coefficient and expressed as the slope of the initial part of the curve as shown in Figures 5-7. In addition, the advantages of the technique, justification and comparison between the present study and other literature works should be written out in a much more detailed and comprehensive manner in Results and Discussion section.

6-   The conclusions perform the findings of the present study in a concrete manner; however, I recommend the authors to add a paragraph on the motives and prospects that this work provides for future research. In addition, I recommend the authors to mention (recommendations) which durability properties should be investigated before it could be proven OK to be used in the future studies.

Author Response

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Reviewer 2 Report

The novelty of the study should be clearly presented.
The experimental methods part needs to be revised. For example in TGA section the authors  referred XRD analysis however the methodology for XRD was missing. 

Author Response

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Reviewer 3 Report

The paper shows the results of resistivity measurements on mortars before and after the capillary absorption test. The measurement of resistivity and water absorbed by capillarity at different ages, and the mercury intrusion porosimetry and DTG curves of samples cured 28 days are presented. The results require a better explanation and understanding of the results yielded by the tests chosen for the study.

Much literature has been published on electrical resistivity testing of concretes and mortars with and without mineral admixtures, and in this paper many of the references on the subject are missing (for example, while there are publications by the RILEM technical committee, none are mentioned in the literature).

In addition, this paper also has shortcomings in the methodology and discussion. When the preparation of the samples is mentioned, it is not detailed according to which standards the mixing, cast and/or curing are carried out (the curing temperature is not mentioned, nor the medium - water, water saturated with lime, air, or self-curing). Only in the results it is stated that compressive strength, MIP and TG are performed on samples cured at 28 days.

Furthermore, it is not known on what type of samples the MIP and TG are performed (whether on pastes or on mortar fractions taken from the samples tested by capillary absorption).

The preparation of the samples for the capillary absorption test is not clear. I suggest that you reference a European or US standard and state the differences in the procedure. How many days are the specimens cured before starting the test? It should also be incorporated at what ages weight and resistivity measurements are taken. 36 days of testing is unreasonably long, since the mortar is saturated by water ascension by capillarity and then the water in the area not immersed begins to evaporate.

On the other hand, in lines 136-140, references from the literature are used to discuss the pore size and the hydration products formed while in later sections of the paper the MIP and TG tests of the samples studied are presented. I suggest that the authors rearrange the order to support with their own samples the behavior of the mortars under capillary absorption.

Figure 3 does not show a significant increase in compressive strength, except for mortars with SF. The authors should specify how much the increase in strength is.

The JZ group is mentioned more than once and reference is made to several samples included in it. However, Table 2 suggests that only one sample is included under this denomination. Similarly, line 133 mentions the "benchmark group", but it is not clear whether this group is the JZ or another.

In lines 278-281 the authors say that "The secondary hydration reaction between the incorporated mineral admixtures and cement hydration product Ca(OH)2 increases the number of gel pores or transition pores in the specimen, decreases the number of macropores and capillary pores, and increases the tortuosity of pores so that the resistivity of the specimen after capillary water absorption is improved.", while in the introduction they say that the decrease in resistivity can generate durability problems and it is shown in Figures 4 that resistivity decreases after capillary absorption in all cases. Therefore, a contradiction is made. Otherwise, they should indicate with respect to what is improving it.

In lines 281-282 the authors make a mistake, since it cannot be the dilution effect that promotes cement hydration. In any case it will be the filler effect generated by the inclusion of fine particles (SF, FA, and SL). In lines 288-291, the sentence contradicts the above. The inclusion of certain SCM promotes hydration at early ages (filler effect) and reduces strength at late ages (dilution), but the authors did not measure TG (or at least it is not presented) at early ages, so the analysis of hydration is not appropriate and should be improved. I suggest that they incorporate more literature and better describe hydration reactions, particularly with SCM.

Moreover, the relationship between cement hydration and porosity, and porosity with compressive strength, capillary absorption and resistivity is not presented throughout the paper. In addition, the authors should include more than one curing age to better understand the effect of including active mineral admixtures on the formed hydration products, porosity, water absorption and resistivity (preferably also include 90 days).

Finally, in the introduction and the purpose, the relationship between water absorption, resistivity and stray currents in underground projects is mentioned and this idea is not mentioned again.

For all these reasons, I do not consider this paper suitable for publication. The discussion and relationships between the parameters studied should indeed be improved.

Author Response

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Reviewer 4 Report

Generally the paper is well written but there are a few shortcomings as below.

The title:

The title refers to the content of the article and analyzed problem.

Section 2.2

-- Line 86:  The abbreviation “JZ” should be written first in full words, as others abbreviations.

Section 2.3

-- Line 103:  To precise origin of the “Test Method for Strength of Cement Mortar”. Is it from the standard, literature, other source ?

Section 3.2

-- Fig 8: Photo in the Figure is not commented. What place of the sample is shown ? What time of water absorption is ?

-- Fig 9: Not precise title of the Fig. Pores in a material can be different, open or closed Here there is a system of capillary pores.

Section 3.3

-- Line 250: Doubtful statement is that in case of SF samples, if number of gel pores increased and  transition, capillary and macropores decreased, “… which significantly increased the tortuosity of the pores in the specimen, …”. This is rather assumption.

Having MIP results, better could be to show comparison of measured tortuosity values of tested specimens. Interesting could be to show as well comparison of porosity of tested mortars.

Section 3.4

-- Line 261:  English of the phrase “cement mortar slurry”. Usually is used “cement paste” or “cement mortar binder”.

-- Line 265:  The abbreviation “AFM” should be written first in full words.

-- Lines 271-274:  To check English of the sentence.

-- Line 277:  The phrase JZ>FA-4>SL>4>SF-3 is not precise because the bar of FA-4 is not higher to the bar of SL-4 in the Fig.13.

-- The section 3.4 presents well done discussion of thermogravimetric analyzes. However there is no comments about meaning of these results on the resistivity or water absorption. In the end such comment could be given. 

Section 5. Conclusions

-- There is no conclusion about importance the results of TG-DTG analyzes for the resistivity or water absorption.

Author Response

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Round 2

Reviewer 2 Report

The manuscript can be considered for publication.

Author Response

Comments: The manuscript can be considered for publication.

Response: Thank you very much for your recognition of our work

Reviewer 3 Report

P. 4: Line 130: Wenner, not "Wennar"; Line 146: What do the authors mean by "carbonization"? Why would the sample carbonize at laboratory temperature?

P. 5: Line 176: the unit of 200 is missing. Line 193: what is "wollastonite"? this is the first time it appears in the text and it is unknown what is meant.

P. 6: L202-207: The authors should use references in that sentence.

P7: L240-241: P. 6: L202-207: The authors should rewrite the sentence "The resistivity of the specimen with SF is the lowest, thus its resistivity is the lowest". It doesn't make sense.

P11: L395: "Cement mortar binder"??. The language should be revised.

In the conclusions the authors talk of gel holes. That is not a term that is commonly used, they should check it.

The authors sometimes use the first person form (e.g., p. 8, L279) and sometimes impersonal forms. They should unify the way they write.

Authors sometimes speak of dopants, others of mineral admixtures and others of cementitious materials. The terminology should be unified. Otherwise, it seems that the different ones in the article are written by different people and does not give a sense of continuity. At the same time, I suggest that you do not use the term dopants as it is not what is commonly used to refer to slag, FA and SF. The absence of uniformity is also read with, for example, the "JZ group". In the materials section, the authors introduce it as the baseline group and then refer to it as the reference group (I think). I suggest that they always use the same words to refer to the materials to make it easier for readers to follow, otherwise sometimes we have to guess whether they mean the same thing or not.

I suggest to revise the english writing.

Author Response

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