Review of 'An overview of hydrophobic treatments and their application with Internal Wall Insulation'

On one hand an interesting overview on hydrophobic treatment of internally insulated walls, that could be a good introduction if you are not familiar with the topic. Written in a way that makes it easy to read. On the other hand, it is not clear to me what the purpose of the paper is and what it adds to the present literature on hydrophobic treatment. The paper covers too many subjects which means that it does not go deep into any of them. Like Nathan, I would therefore consider it as a good conference paper, but it would not qualify for a high-ranked scientific journal.

My specific comments are split in two parts; the first part contains suggestions to improve the content of the paper, while the second part contains some editorial comments.

Suggestions to improve the paper:

Section 3.2 – 3.5 should be rewritten; I suggest to use the references as a support to your main story (which I have not identified, cf. my introductory comment). The present setup presents a lot of details without bringing these into an overall story.

Section 3.3, concerning timing of interventions: please add https://doi.org/10.1016/j.buildenv.2020.107410 as reference.

Switch order of 4.1 and 4.2.

Section 4.1.2 is quite detailed compared with other sections of this paper; consider to rewrite the section and refer the different theories to each other, i.e. including your own opinion, not only referring previous studies (referring also to my comment regarding section 3.2-3.5).

Section 4.2.2: Why do you present the two-stage process in such a detail? This should be common knowledge.

Section 4.3.2, last paragraph, last sentence: To my knowledge nobody relate breathability to include liquid transport. Consider to rewrite.

Section 4.3.3, 2^nd paragraph, last sentence: add ‘or reduction of liquid absorption (Soulios et al, 2020)’.

Section 5, 4^th paragraph, 1^st line: Why do you write ‘perhaps’; explain why these mechanisms are the most important. i.e. why you focus on these in section 5 (this could be explained in the introduction, explaining the structure of the paper).

Section 5.2: According to the headline this is about cryptofloresence, however this is not defined until the last part of second paragraph, after defining another important parameter. Please frontload the definition of cryptofloresence or reconsider the title of this section. In section 5.1, it is labelled ‘damage due to the expansion of salt crystals’.

Section 6, 6^th paragraph: Also Soulios has modelled a hydrophobized brick; refer to 10.1016/j.buildenv.2020.107410 (Soulios, de Place Hansen and Peuhkuri, 2021) and (Soulios 2021) Hygrothermal Performance of Hydrophobized Brick and Mortar: Energy Renovation Through Internal Insulation - Can Hydrophobization Improve the Moisture Safety? Phd. Thesis, Aalborg University 10.54337/aau459966346

Section 6.1-6.3 should be supported by more references to support your statements / discussions.

Section 6.3, last sentence: What you state here as a need was studied by Soulios in the two references mentioned above.

Section 7: Please make this section shorter and less detailed. It should focus on the main findings, not repeating the discussions in previous sections. And add a paragraph indicating the next step; what do you suggest to study further?

Section 5.1, 4^th paragraph:

This paragraph should be expanded, as several authors have studied freezing mechanism over the years, e.g. (Powers & Helmuth, 1953), (Litvan, 1972) and (Setzer, 1977). Also, a reference to thresholds values for frost damage expressed by the critical degree of saturation developed by Fagerlund (1977) would be relevant to add. Critical degree of saturation is shown to be strongly related to porosity and pore size distribution, e.g. (Maage, 1984). Also note that not only the freezing point but also the freeze-thaw behaviour / mechanism is affected by the presence of salts, see e.g. (Springenschmid, 1969, 1972), (Jungwirth, Bayer & Grübl, 1986).

References:

Fagerlund, G. (1977). The critical degree of starvation method of assessing the free/thaw resistance of concrete. Materials and Structures, vol. 10, no. 58, pp. 217-253.

Jungwirth D., Beyer, E., & Grübl, P. (1986). Dauerhafte Betonbauwerke. Substanzerhaltung und Schadensvermeidung in Forschung und Praksis. Beton-Verlag, Düsseldorf.

Litvan, G.G. (1972). Phase transitions of adsorbates: III, Heat effects and dimensional changes in nonequilibrium temperature cycles. J. Colloid Interface Science, vol. 38, no. 1, pp. 75-83.

Maage, M. (1984). Frost resistance and pore size distribution in bricks. Materials and Structures, vol. 17, no. 101, pp. 345-350.

Powers, T.C. & Helmuth, R.A. (1953). Theory of volume changes in hydrated Portland cement paste during freezing. Proc. Highway Research Board, vol. 32, pp. 285-297.

Setzer, M.J. (1977). Einfluss des Wassergehaltes auf die Eigenschaften des erhärteten Betons. Deutsche Ausschuss für Stahlbeton, Heft 280, Berlin.

Springenschmid, R. (1969). Grundlagen und Praxis der Herstellung und Überwachung von Luftporenbeton. Zement und Beton, vol. 15, pp. 19-25.

Springenschmid, R. (1972). Erfahrungen bei der Verwendung von Luftporenbildern im Strassenbau. Betonwerk + Fertigteil-Technik, vol. 38, no. 8, 587-593.

I am not familiar with (Künzel, 1995) and (Sedbauer and Künzel, 2000) referred in the paper and whether they refer to the different theories on frost degradation etc., covered by the above-mentioned references, included in my PhD-thesis in frost resistance (published in 1996, in Danish unfortunately).

Further, I could suggest to study section 4.3 in report D2.2 from the RIBuild project on internal insulation of historic buildings (look for the Knowledge Base -> Research at https://www.ribuild.eu/knowledge-base/#research)

Editorial remarks not already covered by a previous review by Nathan Van Den Bossche:

When listing several references to support a statement: Consider listing references with the newest first. And be careful not to list too many references, as in the last paragraph of Section 3.4.

Section 3.1, 2^nd paragraph: Check the used of ‘(SPAB,1995)’ in first line.

Section 3.2:
Is ‘the treatments was usually missing’ referring to van Hees?
Is the phrase ‘The research presented’ referring to the three references already mentioned? In the same sentence, something is missing between ‘hygrothermal performance’ and ‘consumption rate’. And replace ‘are’ with ‘is’ after ‘impregnation’.

Section 3.3: Check the grammar in 2^nd sentence.

Section 3.4: replace ‘depth’ with ‘Depth’ in 3^rd line.

Section 4.1.1, 2^nd paragraph:
Is ‘This means’ referring to hydrophobic or hydrophilic? And please check the grammar of this sentence.
The text in the parenthesis in 2^nd sentence is superfluous.
In the last sentence please add ‘with water repellants’ after ‘treatment’.

Section 4.1.2, last sentence: Is ‘small amount of residual absorption’ referring to absorption still being present or that it is reduced heavily?

Section 4.2.1,1^st sentence after the bullet lists, 5^th line: Should ‘where’ be replaced by ‘whether’?

Section 4.2.1, 2^nd paragraph after the bullet lists:  replace ‘(Krus, 1998)’ to the end of the sentence.

Section 4.2.1, 3^rd paragraph after the bullet lists, 4^th line: delete ‘the’ in front of ‘moisture’.

Section 4.2.1, 5^th paragraph after the bullet lists, 4^th line: Delete ‘).’
Do. Last sentence: what is ‘this type’ referring to? Please specify.

Section 4.2.1, last paragraph: Be more specific than simply referring to ‘below’.

Section 4.2.2, 1^st paragraph: Delete 2^nd sentence as you refer to this study in the following paragraphs.

Section 4.3.2, last paragraph, 5^th line: ‘only a small impact’; do you mean that the treatment does not affect breathability significantly?

Section 4.3.3, 2^nd paragraph, 3^rd line: delete ‘is’ after ’50mm)’.

Section 4.3.3, 2^nd paragraph the sentence starting at 5^th line: Please replace ‘because’ with ‘as this is directly linked with’, and delete ‘is directly linked’.

Section 5: Add a level 2 headline (5.1) right after the level 1 headline (5).

Section 5, 4^th paragraph, 1^st line: ‘to the external surfaces of masonry’ => surface.

Section 5.1: Merge the two (or three) first paragraphs.

Section 5.1, 5^th paragraph: Which mechanism do you refer to in the last sentence?

Section 5.2: Please use either ‘efflorescense’ or ‘effloresence’. At present, both are used. Similar with ‘cryptofloresence’.

Section 6: Add a level 2 headline (6.1) right after the level 1 headline (6).

Section 6, 1^st paragraph, 5^th line: Please specify which techniques you refer to.

Section 6.2, 1^st paragraph: What does ‘Alle three approaches’ refer to?

Section 6.2, 3^rd paragraph, 4^th line: delete ‘is’ after the parenthesis.

Section 7, 7^th section: This should be placed earlier in section 7.

References: Please use ‘de Place Hansen, E.J.’ in the three references with Soulios as first author, and in (Hansen, Hansen and Soulios, 2021).