The Crystallization Effect of Sodium Sulfate on Some Italian Marbles, Calcarenites and Sandstones

Round 1

Reviewer 1 Report

 

The article provides a lot of interesting information on how to assess the degree of mineralization of the deterioration of limestone and sandstone from architectural elements in the European Mediterranean zone. The survey results of experimental studies are extremely valuable, while the petrographic features of the studied rock samples are less well described. The reviewer recommends checking the numbering of the figures (Figure 2 appears here twice) and correcting the references to them in the text. I also postulate a change in the order of presenting the results of the determination of oxides in Table 1, which should be in line with the principles used in petrology (ie SiO2, TiO2, Al2O3, Fe2O3, MnO, MgO, CaO, P2O5, LOI and Total). The work is consistent in terms of content and is another valuable study devoted to changes in the surface of stone historic buildings as a result of their secondary mineralization.

Author Response

Reviewer 1

The article provides a lot of interesting information on how to assess the degree of mineralization of the deterioration of limestone and sandstone from architectural elements in the European Mediterranean zone. The survey results of experimental studies are extremely valuable, while the petrographic features of the studied rock samples are less well described. The reviewer recommends checking the numbering of the figures (Figure 2 appears here twice) and correcting the references to them in the text.

We thank you for the observation. We corrected the repetition and renumbered the figures.

I also postulate a change in the order of presenting the results of the determination of oxides in Table 1, which should be in line with the principles used in petrology (ie SiO2, TiO2, Al2O3, Fe2O3, MnO, MgO, CaO, P2O5, LOI and Total).

We thank you for the observation. We have rearranged the order of the oxides, according to the use of petrography.

The work is consistent in terms of content and is another valuable study devoted to changes in the surface of stone historic buildings as a result of their secondary mineralization.

Author Response File: Author Response.pdf

Reviewer 2 Report

 

Dear authors this is an interesting piece of work containing valuable information. However, the paper could be improved by improving the English and by clarifying some details in the text. Please find a list of my suggestions below.

 

Comments to individual lines in the paper:

Lines 68 to 70: "Soluble salts are particularly dangerous in rocks characterized by high porosity because they can penetrate easily into the pore structure and cause esthetic and structural damage, but there are also possible hazards to less porous building materials."

It is simply not true that the quantity of porosity of a rock is a decisive factor for its susceptibility for salt damage, which is what your phrase suggests. Think about very porous rocks like pumice, which is probably not susceptible to salt damage because its porosity is not open for salt solutions to penetrate or tufa, where its big pores are not affected by salt damage but its very fine pores are; further there are many cases of heavy salt damage to rocks being only little porous…

Susceptibility to salt damage has much more to do with how the porous network is arranged… Please change the mentioned phrase accordingly.

Lines 73-74: "…rocks have been chosen for their different porosity…" looking at the literature you cite here [41-43] it seems not simply to be porosity (volume proportion of voids of these rock types) but rather their overall petrophysical properties of these rock types?!

Lines 77-78: Change " …when their porosity is more abundant " by " ..after their porosity has been increased…"

Lines 97-98 Figure 1. Caption: "…Cubic specimens have 5 cm long sides" the images of the stones are not squares but rectangles. So, which of the sides are 5 cm?

Lines 106-107: " ..transmitted light microscopic observations of thin sections…" – better " polarized light microscopy on thin sections"

Line 116: " wet-drying" this would mean drying under wet conditions but I suppose it should be something like "…subsequent cycles of wetting and drying …"

Line 119: " can be calculate" needs to be " can be calculated"

Line 126: " to store the" better " to record the"

Line 128: " ..among our samples only calcarenite ones..," better " among our samples only calcarenites…"

Line 133: " exposition" probably "exposure" would be more appropriate

Line 133-134: " We weighted the specimens at the end of every cycle" How did you avoid loss of material from the stone by mechanical abrasion during this process? Or why was this no problem?

Lines 136: " have not been brought to high temperatures, …" " that have not been subjected to thermal degradation…" seems easier to understand for the reader…

Line 147: " From chemical point of view" needs to be " From the chemical point of view"

Line 148: " similar each other needs to be " similar to each other"

Line 149: " …of a little more amount of…" …should be " of a little more …"

Line 149: " in respect to marbles" better "compared to marbles"?

Lines 150-151: " In addition, the marble samples are characterized by a higher content of chemical components referred to carbonates (LOI, CaO and MgO) than the calcarenite" could be replaced by " In addition, the marble samples are characterized by a higher content of LOI, CaO and MgO than the calcarenite" (the part of the phrase " chemical components referred to carbonates" seems in itself incorrect, it would need to be " carbonate rocks" instead of "carbonates" which itself means a salt of carbonic acid…)

Line 168: " the first one that can appear" better " with calcite appearing…"

Line 173: " percentage" better " percent" The word appears twice in this line

Line 177: " The two samples of calcarenites " please give their names (MPS and MAS) the reader is not forcibly so familiar with the abbreviations used and their meanings …

Line 179: " there are substantial difference" needs to be " there are substantial differences"

Line 198: " and apparent density decrease" needs to be " and apparent density decreases"

Lines 199-200: " and some samples met the requirements of the application of the European Norms" what do you want to say with that? Which Norms you refer to – all Norms mentioned in the paper? What are these requirements?

Line 202: " application of the norm" please cite the norm you refer to

Line 203: " underwent 500°C (C) decay" what stands the (C) for? The whole paragraph is difficult to understand. I have seen later that A, B and C refer to the temperatures used to treat the samples. This should be clearly explained. Maybe by giving a table that explains all names and abbreviations?

Line 211: " the wet-drying cycles" as comment for line 116

Line 211: " it has been observed the presence of efflorescence" better " the presence of efflorescence has been observed "

Line 214-215: " Fresh and thermally degraded specimens showed different relative mass percentage loss." …after brushing???  Probably not. This paragraph needs to be built up more clearly

Line 218: " average relative mass percentages" mass percent of what? loss? Replace percentage by percent, also in line 219

Line 225-226: "MPS drop its mass over than 20% just after…" suggestion for better phrasing " MPS loses more than 20% of its mass just after…"

Line 226: what is meant with " and breaks over"? Figure 2 did not explain it to me

Lines 227 to 229: " It is also slightly different the rate of mass loss, with MAS that appear to be a little slower in its disintegration than MPS, but the remarkable difference is about the time that the specimens need to break under the attack of the saturated salt solution." I do not understand this whole phrase in general and more specifically what is meant exactly with "the time the specimens need to break"?  How is the "breaking" manifested (split apart?)? How is it defined?

Line 230: "Once the process begins," which process?

Line 231: " even the salt crystallization…" the weight gain is related to the uptake of salt, but not to its crystallisation! In other words, even if the salt was present within the sample in an amorphous form there still would be a weight gain – needs to be rephrased

Line 242-243: " due to its best petrographic features. " better " due to its better properties in comparison to the other tested rocks…" – (petrography = description of rocks – "petrographic feature" seems not correct to me; if "petro" needs to remain in the sentence it would rather be "petrologic features")

Line 257: " Loss of mass is remarkable in" – remarkably high or remarkably low or "remarkable" in the sense "can be observed"?

Lines 260-264: " Sodium sulphate crystallizes as sub-efflorescence inside the stone where the porosity allowed it: the saturated solution penetrated through the pores and when the specimens were dried, the humidity was low enough to trigger crystallization in outer- most layers of the rocks, causing pressure from the crystals with consequential cracking and disintegration" I suppose this was observed during your tests? If yes please say so. The English needs revision

Line 272-273: "wet-drying cycles" as comment for line 116

Line 278: Figure caption, please indicate what the letters A,B and C in the figure represent. Same remark for similar figures later in the paper

Line 279: " where the warmest specimens break at the same cycle" how is "break" defined? Isn't the degradation of the samples gradual? From the figures I guess, that "break" is when weight loss reaches 20% or more ?

Line 293: " salt soluble crystallization resistance" = resistance to soluble crystallisation of salts! Better would be "resistance to crystallisation of soluble salts"

Line 299: "degradation, but on a small scale also they show the decay process" replace by "degradation, but on a small scale they also show the decay process"

Line 317: "petrographic characteristics and physic properties" Please verify that petrographic is correct here, to my opinion it should rather be petrologic; "physic" needs to be replaced by "physical"

Lines 318-320: The whole phrase is not clear. Are these your observations or are there citations missing?

Line 319: What do you mean by "with an insolation, and therefore a heating"? Can you give an example?

Lines 322-323: "but we want to emphasize …" why "but" and not "and"?

Line 326-327: "…lost more mass percentage in less cycles…" The word "percentage" is not necessary; if you want to keep the notion you could replace the phrase by "relatively lost more mass in less cycles…"

Line 327: " In environments where the overheating of the materials is constant" what is meant by "constant"? regularly/frequently? It would be good to give an example and/or cite a paper or to describe places like that of your own observation.

Author Response

Reviever 2

Dear authors this is an interesting piece of work containing valuable information. However, the paper could be improved by improving the English and by clarifying some details in the text. Please find a list of my suggestions below.

Comments to individual lines in the paper:

 

Lines 68 to 70: "Soluble salts are particularly dangerous in rocks characterized by high porosity because they can penetrate easily into the pore structure and cause esthetic and structural damage, but there are also possible hazards to less porous building materials."

It is simply not true that the quantity of porosity of a rock is a decisive factor for its susceptibility for salt damage, which is what your phrase suggests. Think about very porous rocks like pumice, which is probably not susceptible to salt damage because its porosity is not open for salt solutions to penetrate or tufa, where its big pores are not affected by salt damage but its very fine pores are; further there are many cases of heavy salt damage to rocks being only little porous…

Susceptibility to salt damage has much more to do with how the porous network is arranged… Please change the mentioned phrase accordingly.

We thank the reviewer for the comment and are in complete agreement with his observation. Without changing the sentence too much, we specified that we are talking about open porosity, connected through a dense network of pores, through which salts can circulate dissolved in liquids and settle when the conditions of pressure and temperature change.

Lines 73-74: "…rocks have been chosen for their different porosity…" looking at the literature you cite here [41-43] it seems not simply to be porosity (volume proportion of voids of these rock types) but rather their overall petrophysical properties of these rock types?!

The works cited report a series of chemical-physical properties in addition to porosity, which we have decided to consider only marginally, focusing our attention on porosity

Lines 77-78: Change " …when their porosity is more abundant " by " ..after their porosity has been increased…"

We have made the required correction in the text.

 

Lines 97-98 Figure 1. Caption: "…Cubic specimens have 5 cm long sides" the images of the stones are not squares but rectangles. So, which of the sides are 5 cm?

These are cubes of 5 cm on each side. The deformation that can be observed in the figure and which makes them appear rectangular is due to a distortion of the image due to a resize operation useful for pagination in the article. We tried to correct the distortion as best we could.

Lines 106-107: " ..transmitted light microscopic observations of thin sections…" – better " polarized light microscopy on thin sections"

We have made the requested correction.

Line 116: " wet-drying" this would mean drying under wet conditions but I suppose it should be something like "…subsequent cycles of wetting and drying …"

We have made the requested correction.

Line 119: " can be calculate" needs to be " can be calculated"

We have made the requested correction.

Line 126: " to store the" better " to record the"

We have made the requested correction.

Line 128: " ..among our samples only calcarenite ones..," better " among our samples only calcarenites…"

We have made the requested correction.

Line 133: " exposition" probably "exposure" would be more appropriate

We have made the requested correction.

Line 133-134: " We weighted the specimens at the end of every cycle" How did you avoid loss of material from the stone by mechanical abrasion during this process? Or why was this no problem?

Right observation. During each weighing cycle, we paid particular attention to ensure that there were no mass losses from the sample, carefully handling each of them and carefully checking that there were no leaks.

Lines 136: " have not been brought to high temperatures, …" " that have not been subjected to thermal degradation…" seems easier to understand for the reader…

We have made the necessary correction in the text, for the purpose of better readability and clarity.

Line 147: " From chemical point of view" needs to be " From the chemical point of view"

We have made the requested correction.

Line 148: " similar each other needs to be " similar to each other"

We have made the requested correction.

Line 149: " …of a little more amount of…" …should be " of a little more …"

We have made the requested correction.

Line 149: " in respect to marbles" better "compared to marbles"?

We have made the requested correction.

Lines 150-151: " In addition, the marble samples are characterized by a higher content of chemical components referred to carbonates (LOI, CaO and MgO) than the calcarenite" could be replaced by " In addition, the marble samples are characterized by a higher content of LOI, CaO and MgO than the calcarenite" (the part of the phrase " chemical components referred to carbonates" seems in itself incorrect, it would need to be " carbonate rocks" instead of "carbonates" which itself means a salt of carbonic acid…)

We thank you for the observation. We have made the necessary corrections in the text.

Line 168: " the first one that can appear" better " with calcite appearing…"

We have made the requested correction.

Line 173: " percentage" better " percent" The word appears twice in this line

We have made the requested correction.

Line 177: " The two samples of calcarenites " please give their names (MPS and MAS) the reader is not forcibly so familiar with the abbreviations used and their meanings …

We added in the text.

Line 179: " there are substantial difference" needs to be " there are substantial differences"

We have corrected the sentence.

Line 198: " and apparent density decrease" needs to be " and apparent density decreases"

We have corrected the sentence.

Lines 199-200: " and some samples met the requirements of the application of the European Norms" what do you want to say with that? Which Norms you refer to – all Norms mentioned in the paper? What are these requirements?

We have modified the text in this way: EN 12370 on the determination of resistance to salt crystallisation (open porosity > 5% by vol.).

Line 202: " application of the norm" please cite the norm you refer to

We added in the text: (EN 12370).

Line 203: " underwent 500°C (C) decay" what stands the (C) for? The whole paragraph is difficult to understand. I have seen later that A, B and C refer to the temperatures used to treat the samples. This should be clearly explained. Maybe by giving a table that explains all names and abbreviations?

We deleted A, B, C.

Line 211: " the wet-drying cycles" as comment for line 116

We have corrected the sentence.

Line 211: " it has been observed the presence of efflorescence" better " the presence of efflorescence has been observed "

We have corrected the sentence.

Line 214-215: " Fresh and thermally degraded specimens showed different relative mass percentage loss." …after brushing???  Probably not. This paragraph needs to be built up more clearly

As reported in the text, before drying the specimen has been washed and cleaned (paying attention to not damage its) with a soft paint brush.

Line 218: " average relative mass percentages" mass percent of what? loss? Replace percentage by percent, also in line 219

We have corrected the sentence.

Line 225-226: "MPS drop its mass over than 20% just after…" suggestion for better phrasing " MPS loses more than 20% of its mass just after…"

We have corrected the sentence.

Line 226: what is meant with " and breaks over"? Figure 2 did not explain it to me

We have changed the sentence in the text.

Lines 227 to 229: " It is also slightly different the rate of mass loss, with MAS that appear to be a little slower in its disintegration than MPS, but the remarkable difference is about the time that the specimens need to break under the attack of the saturated salt solution." I do not understand this whole phrase in general and more specifically what is meant exactly with "the time the specimens need to break"?  How is the "breaking" manifested (split apart?)? How is it defined?

We have rewritten the sentence.

Line 230: "Once the process begins," which process?

We have modified the sentence.

Line 231: " even the salt crystallization…" the weight gain is related to the uptake of salt, but not to its crystallisation! In other words, even if the salt was present within the sample in an amorphous form there still would be a weight gain – needs to be rephrased

We have modified the sentence.

Line 242-243: " due to its best petrographic features. " better " due to its better properties in comparison to the other tested rocks…" – (petrography = description of rocks – "petrographic feature" seems not correct to me; if "petro" needs to remain in the sentence it would rather be "petrologic features")

We have corrected the sentence.

Line 257: " Loss of mass is remarkable in" – remarkably high or remarkably low or "remarkable" in the sense "can be observed"?

We have modified the sentence.

Lines 260-264: " Sodium sulphate crystallizes as sub-efflorescence inside the stone where the porosity allowed it: the saturated solution penetrated through the pores and when the specimens were dried, the humidity was low enough to trigger crystallization in outer- most layers of the rocks, causing pressure from the crystals with consequential cracking and disintegration" I suppose this was observed during your tests? If yes please say so. The English needs revision

We have modified the sentence.

Line 272-273: "wet-drying cycles" as comment for line 116

We have modified the sentence.

Line 278: Figure caption, please indicate what the letters A, B and C in the figure represent. Same remark for similar figures later in the paper

We changed letters A, B and C with 200°C, 350°C and 500°C.

Line 279: " where the warmest specimens break at the same cycle" how is "break" defined? Isn't the degradation of the samples gradual? From the figures I guess, that "break" is when weight loss reaches 20% or more ?

We have modified the sentence.

Line 293: " salt soluble crystallization resistance" = resistance to soluble crystallisation of salts! Better would be "resistance to crystallisation of soluble salts"

We have corrected the sentence.

Line 299: "degradation, but on a small scale also they show the decay process" replace by "degradation, but on a small scale they also show the decay process"

We have corrected the sentence.

Line 317: "petrographic characteristics and physic properties" Please verify that petrographic is correct here, to my opinion it should rather be petrologic; "physic" needs to be replaced by "physical"

We have checked and corrected the sentence

Lines 318-320: The whole phrase is not clear. Are these your observations or are there citations missing?

We have rewritten the sentence.

Line 319: What do you mean by "with an insolation, and therefore a heating"? Can you give an example?

We have rewritten the sentence.

Lines 322-323: "but we want to emphasize …" why "but" and not "and"?

We have corrected the sentence.

Line 326-327: "…lost more mass percentage in less cycles…" The word "percentage" is not necessary; if you want to keep the notion you could replace the phrase by "relatively lost more mass in less cycles…"

We have corrected the sentence.

Line 327: " In environments where the overheating of the materials is constant" what is meant by "constant"? regularly/frequently? It would be good to give an example and/or cite a paper or to describe places like that of your own observation.

We have changed the sentence.

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Editor,

 

Thank you for the opportunity to review the paper entitled "Study of the effect of salt crystallization on natural stones". The paper is well-structured and written in the scientific manner. The paper deals with the decay effect of the sodium sulphate crystallization on the chosen natural stone samples. The obtained results are interesting and practically useful. Nevertheless, there are a few things that should be added/changed before the further process of publication.

 

Some of my overall comments for this paper:

 

-          Abstract part:

lines 12-13- Please, rephrase the sentence and emphasize the problem of salt crystallization in a better manner;

Line 15: Sodium sulphate has a great impact in the constructions, but also on their surface. Please, correct …. in constructions;

Line 17: Please, write freshly made instead of fresh samples

Also it is necessary to put some exact results gained through experiments in the abstract part

-          Introduction part:

Lines 34-36: Not all laboratory studies follow this regime for artificial contamination of specimens with different salts. More precisely, sometimes there is no drying of the specimens in the oven, but drying in the air

Line 43: change as to called

Lines 43-44: The written sentence is partially correct. Namely, the efflorescence seems to cause just aesthetic problem, but the salts on the surface of the materials are great environment for the microbial growth.

Line 70: Indicate which structural damage could be caused by the presence of the soluble salts

The novelty of the work should be emphasized at the end of the Introduction part

-          Materials and methods:

-          Line 109: Indicate the producer and type of the used XRPD for the analysis

-          Results and discussion:

After each presented Table should add explanation of the abbreviations used for the samples

Line 211: Was the presence of the efflorescence observed ad oculi or by microscope?

For the Figures 5 and 6 add exact name and the written explanations and descriptions should be transferred to the following text.

Lines 298-303: Are these findings supported by the other authors?

-          Conslusions:

Please, add some future perspectives according to the obtained results

-          References:

The number of references is good, but they are quite outdated. This part should be revised and some new results in this area should be added in the Introduction part as well as in Results and discussion.

Author Response

Reviever 3

Dear Editor,

Thank you for the opportunity to review the paper entitled "Study of the effect of salt crystallization on natural stones". The paper is well-structured and written in the scientific manner. The paper deals with the decay effect of the sodium sulphate crystallization on the chosen natural stone samples. The obtained results are interesting and practically useful. Nevertheless, there are a few things that should be added/changed before the further process of publication.

 

Some of my overall comments for this paper:

 

-          Abstract part:

lines 12-13- Please, rephrase the sentence and emphasize the problem of salt crystallization in a better manner;

We have rewritten the sentence.

Line 15: Sodium sulphate has a great impact in the constructions, but also on their surface. Please, correct …. in constructions;

We have corrected the sentence.

Line 17: Please, write freshly made instead of fresh samples

We have corrected the sentence.

Also it is necessary to put some exact results gained through experiments in the abstract part

We have included a short sentence to indicate the results of this study.

-          Introduction part:

Lines 34-36: Not all laboratory studies follow this regime for artificial contamination of specimens with different salts. More precisely, sometimes there is no drying of the specimens in the oven, but drying in the air

We have corrected the sentence.

Line 43: change as to called

We have corrected the sentence.

Lines 43-44: The written sentence is partially correct. Namely, the efflorescence seems to cause just aesthetic problem, but the salts on the surface of the materials are great environment for the microbial growth.

We have corrected the sentence.

Line 70: Indicate which structural damage could be caused by the presence of the soluble salts

From line 51 to line 53 we have the sentence: “In this case, salts expanding their volumes or changing their shape can cause pressure and stress to the outermost layers of the rocks, and generate form of decay like cracking, disintegration or delamination [29]”.

The novelty of the work should be emphasized at the end of the Introduction part

We have added a short sentence to point out the novelty of the work.

-          Materials and methods:

Line 109: Indicate the producer and type of the used XRPD for the analysis

We insert the model of XRD.

 

-          Results and discussion:

After each presented Table should add explanation of the abbreviations used for the samples

We add an explanation in Table 1.

 

Line 211: Was the presence of the efflorescence observed ad oculi or by microscope?

We observed the efflorescence ad oculi or by stereomicroscope.

 

For the Figures 5 and 6 add exact name and the written explanations and descriptions should be transferred to the following text.

We have modified the figures.

 

Lines 298-303: Are these findings supported by the other authors?

??????

 

-          Conslusions:

Please, add some future perspectives according to the obtained results.

We have inserted the short sentence for future perspective.

 

-          References:

The number of references is good, but they are quite outdated. This part should be revised and some new results in this area should be added in the Introduction part as well as in Results and discussion.

 

We added some references.

Author Response File: Author Response.pdf

Reviewer 4 Report

Dear Authors,

Please refer to the uploaded file. All suggestions and comments are given in a positive and constructive tone with respect to the authors expertise. The paper was an interesting read, I believe it can be helpful for the community after some changes have been made to clarify the processes and the experimental method. 

Kind regards

Comments for author File: Comments.pdf

Author Response

Reviever 4

Check on the PDF file.

We thank you for the suggestions and observations that we have accepted modifying accordingly the text considering all the requests from the other reviewers.

Author Response File: Author Response.pdf

Round 2

Reviewer 4 Report

The changes have improved the overall read and have addressed some theoretical inaccuracies of the paper. Some concerns persist, yet the results are clear and interesting to built on future work, thus accept in present form.

Author Response

We thank the reviewer for its interesting suggestions that allowed to significantly improve our paper.

Author Response File: Author Response.pdf