Stabilization of Road Embankments on Peat Soils Using Oil Shale Ash and Pozzolanic Additives

Round 1

Reviewer 1 Report

Review

Stabilization of road embankments on peat soils using oil shale ash and pozzolanic additives

 

The detailed description of the experimental study leading to the establishment of road on peat soil was provided. The overall study is interesting but the manuscript is chaotic and not well-balanced. The experimental description is too long, the description of the results and discussion is insufficient. The detailed comments are listed below:

The authors use the expression peat soil, peaty soil or soil containing peat – please be precise and name the soil you are studying. Moreover, on what basis did you classify the soil? In table 1 the organic matter is low suggesting that the soil is not organic. How did you determine organic matter and mineral matter contents (method)? Why mineral matter plus organic matter do not make 100%??

Line 21: what is road soil?

Line 31 and 86: low pH values are not the consequence of high humic acids contents

Line 68: including “floating roads”; in the case of is unnecessary

Line 69-71: please specify the depths/thicknesses of subsoil that is stabilized and “the rest of the subsoil”

Line 81: silicates?; aluminate or aluminum contents?

Line 85: can be adsorbed

Line 87: please specify what kind of effect of humic acids do you have in mind

Lines 101-105: the sentence is too long, make 2 sentences

Lines 116-117: you write that geologically it is a good place for peat formation but you do not specify the conditions or references. In the next sentence, contrary to the previous, you write that this are has different geology – but different from what?

Table 1: In peat soils the organic matter content is much higher, even 90%. The results provided in the table suggest that the soil is not organic. Moreover, the soil consists of mineral and organic matter which summed should be 100%. What is beside organic and mineral matter in your soil?

In line 114 you say that the peat layer is 3 m but in lines 120-124 you write that it is thinner – please correct and be precise or add additional description

For table 1 and 2 there are no methods of analyses provided. I can only assume what methods were used.

In table 2: for Cyclone “PF” should be added

In table 3: The table heading should be Characteristics of three types of silica fume used in the study. Please also change the font type.  

Line 162-165: Why did you collect water?

Line 182: …. in Table 4. Consequently, 12 …….

There are too many Photos, I suggest to reduce most of them (especially the photos with the apparatus) because the description of the experiment is described in detail. I would also suggest to name Chapter 4 "Materials and methods" and provide the description of methods.

When you give a figure caption “(…) components/mixture”, please write these components (or composition of mixture) in brackets.

In table 6 – are the weights of components in kg of fresh matter or dry matter?

In table 7 – please write that these are only for field studies

The chapter 4 is very detailed but lacks the description of the methods used for the determination of chemical analyses.

Lines 364-366, 370-384, 413-415, 440-442: the methods should be provided in the previous chapter.

Line 396: Table xxx – where is it??

Line 461, and also other parts of the text: please provide the scientific description of figures and do not use expressions like “swan neck-shaped”; moreover if you are describing a figure, please provide the figure number in the brackets.

Line 471: what is the creep limit?

Line 512: please rewrite the sentence.

Line 513: current study, not work

Line 530: The water regime of peatland was not studied, therefore you can not say that it was not changed. Water regime studies are carried out on larger areas, which was not included in your experiments.

Line 531: avoiding negative impacts on biodiversity – I would be careful with such statements. You haven’t studied it.

Author Response

All responses in one file

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript contains new interesting results of testing peat soil stabilization using traditional geopolymerization agents (like cement, fly ash or silica) and catalysts (like NaOH). A distinctive feature and an undeniable advantage of the study is the conduction of experiments at all levels from laboratory to field as well as a significant number of nice photos. The main flaws of the manuscript include the poor structure of the text (the Introduction consists of two parts, there is no aim of the study, the experiment is described in insufficient details, the Results section often contains information related to other sections, etc.) and an insufficiently well description of the results (there is no discussion and comparison with the results of other authors or other stabilized substrates, their own results are described very sparsely, therefore the specific values given in the Conclusion do not seem obvious, etc.).

 

Particular comments

Abstract: should be re-written. The sentence "In this study, an exhaustive investigation of chemical processes allows us…" should be deleted, since this study is based on existing ideas about the chemistry of geopolymerization processes, and does not study them. The summary should include information about the specific results obtained in the work, with specific values

line 38: please decipher Cu

line 56-57: I would recommend to delete the sentence

Subsections 1 (Introduction) and 2 (Chemical processes during the hardening of concrete materials in environments with high humic acid concentrations) should be combined to make Introduction

lines 81-82: repetition (lines 31-32)

line 92: please add an explanation of the term C-S-H gel (calcium silicate hydrate)

lines 91-95: please add a reference where the described phenomenon has been demonstrated

lines 96-98 please add a reference where the described phenomenon has been demonstrated

line 109: please specify here an aim of the study

line 114: please re-write the sentence "The soil at the test site is peat with a layer thickness of 0–3 meters". The thickness cannot be 0 m

line 124: please add a short description of sampling procedure: what was a sample size, what was a depth of sampling etc.

lines 126-128: please remove or move into the Introduction

lines 129-134: please remove or move into the Introduction

lines 135-147: please re-write in a way to describe the specific samples used in this study excluding general information; descried how the mineral content has been determined

line 157: please describe how particle size and silica content have been determined or specify the origin of the data

line 163-165: please describe how bog water has been sampled and how organic matter has been determined

line 168-169: unclear, Table 1 contains description of 20 variants rather than 57

lines 170-174: please describe more detailed, wet or dry peat samples were used, was there a preliminary preparation of peat samples or not, how peat samples were mixed with additives, what was the sequence of adding additives etc.

lines 183-184: please specify what were "standard containers" and "compressive strength measuring apparatus"

line 193: please add the manufacturer and country for the equipment used; check this point for all facilities thought the manuscript

lines 202-205: please specify what peat sample was used for the experiments

line 228: T17? what is this?

line 243: delete the sentence

lines 326-330: this information seems to be excessive in terms of a scientific paper and can be excluded

line 333: what was the "working depth"? how " the soil was loosened"?

Table 7: please specify "ash" and "silica" used in the experiment

line 347: please describe how ash has been spread and mixed with soil

lines 358-360: this information should be placed in the Materials and Methods section, not in the Results section

Table 8: Spaceman's names do not correspond to those in Table 4, please, correct. Please add statistical information

lines 365-366: this information should be placed in the Materials and Methods section, not in the Results section

Table 9: please decipher Rwp and Rwp'

lines 370-381: this information should be placed in the Materials and Methods section, not in the Results section

lines 381-384 information concerning measurements procedure should be placed in the Materials and Methods section, not in the Results section

Table 10: please indicate the meaning of +/-

lines 387-391: please specify the experimental data (figure or table) on the basis of which this conclusion is made

line 391: Figure xxx?

line 396: Table xxx?

lines 413-415: this information should be placed in the Materials and Methods section, not in the Results section

Table 11: please indicate the meaning of +/-, what is "Bag 1"? All the samples' names used in the Results section should be introduced in the Materials and Methods section

Table 12: what are "samples 1–5" here?

Table 13: all the indexes used in the table should be deciphered; please add statistical data; all the samples' names used in the Results section should be introduced in the Materials and Methods section

Table 14: bad table name; all the samples' names used in the Results section should be introduced in the Materials and Methods section; please add statistical data; replace the decimal separator with a dot

Figure 23, 24: completely unclear. How presented data were obtained? What samples were tested? There are no references to these figures in the text

lines 479-481: please add a reference

lines 482-510: this part of the text is a mixture of information related to the Materials and Methods section and descriptions of the results, but without references to figures or tables. In this regard, its meaning is very difficult to understand, the text should be rewritten

Author Response

All responses in one file

Reviewer 3 Report

Stabilization of peat soils for load embankment using oil shale ash is discussed in the manuscript. In addition, several reagents are also considered. The attempt is interesting. However, the manuscript does not maintain the form of technical article. Although rational and strategic study process should be shown, conducted tests are just orderly described. The results can be summarised more concise using just what is needed. Moreover, shear strength describing as "compressive strength", which is the most important soil constant, is not clear. Specimen's height needs to 1.5 times or more than its diameter to evaluate shear strength in compression tests. Therefore,  the reviewer cannot confirm their reliability. 

The reviewer can understand the English meanings in the manuscript. However, more concise and plain English is required.

 

Author Response

All responses in one file

Round 2

Reviewer 1 Report

The weak points of the paper has not been removed yet. 

First of all, mineral matter and organic matter contents constitute 100% of the solid mass. You can not include water content  - this is a methodological failure (100% - organic matter content% = mineral matter content%). 

The amount of photos was not reduced but several photos has been put as a single figure. The photos of apparatus are unnecessary. Only the photos which show the experimental site, materials, or scientific approach, should be present. 

In Figure captions or table headings lack the "space". In tables various fonts were used. Some of the table headings provide the heading and some are still to laconic. SOme tables could also be removed or the data could be included as a sentence (for example Table 5). Please do not duplicate the Figure captions (for example Figure 11, 12, others also; name the graphs A and B instead of duplication of sentences; inlude the units in the captions). In figure 12 - some of information is missing. 

In my opinion some of the weak points has been removed but the paper still requires corrections. The authors provided the answer to the reveiewer's  comments but did not include some of the explanations in the text. 

I suggest to correct the tables, fonts and table headings (they should describe the contents of the table), reduce the figures, correct the figure captions. Some of the tables should be included as supplementary material - this would make the paper less chaotic. 

Author Response

The English of the manuscript has been improved by language editing.
The data shown in Table 1 have been recalculated to exclude water from the composition of soil, so that the soil mass is constituted of mineral and organic matter only.
Photos of equipment removed.
All the tables reformatted.
Changes have been made in figures and figure captions taking into consideration the reviewers’ suggestions.

Reviewer 2 Report

The authors replied almost all the remarks. In some cases I still do not agree to the structure of the text. However, these points are not essential in this case. The only point is still questionable. I could not understand the authors' reply which was "Jüri sa oled sellega paremini kursis kui mina". However, I could not find added statistical data to the values presented in Table 12 and 13. The manuscript can be accepted after adding standard deviations.

Author Response

Sorry, some comments from one author to another in Estonian were somehow left in replies’ file.
The experiments were arranged in such a way that the results of each previous series were the basis for the choices on which each subsequent series was organized. Measurements of mechanical properties were destructive, ending with the breakage of the respective test piece. Therefore, each measurement was performed once, statistical calculations were not prformed, and standard deviations cannot be presented.

Reviewer 3 Report

The authors insist in the authors' response that the tests are conformed to the standards. Therefore, the reviewer checked the standard of CEN ISO/TS 17892-7:2004. The standard requires following items: 

5.1.2 For cylindrical specimens the ratio between height and diameter shall be between 1,8 and 2,5. For square specimens the ratio between height and length of side shall be between 2,0 and 2,8.

 

The specimen dimensions used in the study do not follow this standard. Therefore, the authors have to describe the reasons why nonconforming methods were used. In addition, they should discuss the effects of nonconforming on their results. Otherwise, we cannot confirm the reliability of the tests.

 

Moreover, the ISO standard has already published for this standard: ISO 17892-8: 2018. In the future, this standard should be used.

 

The reviewer can understand the English meanings in the manuscript. However, more concise and plain English is required.

 

Author Response

The tests were performed as part of the master's thesis of one of the co-authors of this manuscript. The determination of the shear strength was based on the work instructions of the Geotechnical Laboratory of the Estonian Environmental Research Center STJnrG25. The STJnrG25 work manual was based on the standard CEN ISO/TS 17892-10:2004: Geotechnical investigation and testing – Laboratory testing of soil – Part 10: Direct shear tests, but some changes compared to the standard were possible. These tests were indicative, the following tests were planned based on them. In the final tests, measurements were performed in accordance with the above-mentioned standard.
Uniaxial compression tests were carried out in accordance with the STJnrG22 standard work manual of the Estonian Environmental Research Geotechnical Laboratory, which was prepared based on the standards:
GOST-12248-96: Soils. Laboratory methods for determining the strength and strain characteristics
CEN ISO/TS 17892-7:2004: Geotechnical investigation and testing – Laboratory testing of soil Part 7: Unconfined compression test on fine-grained soil
For uniaxial compression tests, test specimens with dimensions of 50x50x50 millimeters were used.
The compressibility test, or oedometer test, was prepared based on the standard work manual STJnrG20 of the Geotechnical Laboratory of the Estonian Environmental Research Center. The standard guide was compiled based on the standards:
EVS-EN ISO17892-5:2017: Geotechnical investigation and testing – Laboratory testing of soil. Part 5: Incremental loading oedometer test (ISO 17892-5:2017)
GOST 12248-96: Soils. Laboratory methods for determining the strength and strain characteristics
The main difference between the two standards lies in the selection of the load range (STJnrG20).
When performing compression tests on natural soil, the load levels were used: 0.005MPa, 0.01MPa, 0.02MPa, 0.04MPa, 0.08MPa, 0.16MPa, 0.32MPa. At all load levels, the length of loading was 12 hours. Decompression was carried out at a load level of 0.005 MPa and the duration of decompression was 2 hours.
When carrying out the compression tests of the mixed mixture in outdoor conditions, the load levels were used: 0.01MPa, 0.02MPa, 0.04MPa, 0.08MPa, 0.16MPa, 0.32MPa. At all load levels, the length of loading was 12 hours. Decompression was performed at a load level of 0.01MPa and the duration of decompression was 2 hours.
The text of the revised manuscript has been proofread by a professional English language editor.

Round 3

Reviewer 1 Report

no comments

Author Response

No comments

Reviewer 3 Report

The reviewer cannot find the revised parts based on reviewer's previous comments.

 

The reviewer can understand the English meanings in the manuscript. However, more concise and plain English is required.

 

Author Response

Replies to Comments and Suggestions for Authors, 3rd revision, applsci-2395327

Reviewer’s comment: Comments and Suggestions for Authors

The reviewer cannot find the revised parts based on reviewer's previous comments.

Reply: The following text was added in “track changes” to chapter 4.4.2. Shear strength tests:

The tests were carried out as part of Andrus Leinpuu's master's thesis and were considered indicative, enabling the selection of the optimized composition of the mixture used in the final field tests (see chapters 4.3 and 5.5). In this regard, the solidified test specimens were treated not as mass-stabilized soil, but as lightweight concrete with organic fillers, and the tests were performed according to the national standard “EVS-EN 12390-3:2019 Testing hardened concrete - Part 3: Compressive strength of test specimens”, using the equipment available in the research group's laboratory. The standard allows the use of cube or cylinder shaped specimens or drill cores as test pieces. The corresponding ISO standard is “ISO 1920-6 Testing of concrete — Part 6: Sampling, preparing and testing of concrete cores”.

The following text was added in “track changes” to chapter 4.4.3. Compressibility tests:

 

Reviewer’s comment: Comments on the Quality of English Language

The reviewer can understand the English meanings in the manuscript. However, more concise and plain English is required.

Reply: The text of the manuscript has been proofread by a professional scientific editor from a MDPI language-editing service company. The changes made have been indicated in “track changes” in the revised manuscript.