Optimization of Soil to Fly-Ash Mix Ratio for Enhanced Engineering Properties of Clayey Sand for Subgrade Use
Round 1
Reviewer 1 Report
The manuscript is about a laboratory investigation to determine the optimum soil to fly-ash mix ratio to improve the engineering properties of clayey sand for road projects. There are few suggestions/comments as follows:
- Table 2 showed that 40% Fly-ash has the highest MDD, higher than 50% Fly-ash. Also, Figure 5 showed that 50% Fly-ash has the highest UCS, higher than 40% Fly-ash. Please describe why the 40% Fly-ash despite having the highest MDD value did not obtain the highest UCS.
- The trend lines in Figure 6, which are used to be able to get the UCS values between 8-28 days curing period, might be not appropriate. The trend lines in Figure 5 is more general than those in Figure 6. Therefore, the reviewer suggests that the authors may omit Table 3 and Figure 6, or provide related reference data.
- The manuscript should show or provide pictures of the “before and after” of the specimen during the UCS tests.
- Lastly, referring to wrong figure number within the manuscript brings confusion and misinterpretation to the readers. Kindly check and give the correct figure number to the following: (a) Lines 157-158 (Page 7). There is no Figure 11 in the manuscript. (b) Lines 223-253 (Pages 10-12) discuss about Figure 6 and Table 3. However, in Table 3 under the “Fitted Polynomial Equation” column, the authors wrote “As shown in Figure 8”, but the R² values matched with those in Figure 6 and not in Figure 8. Did the authors mean to write Figure 6? Kindly check also Line 225 (Page 10). (c) Lines 263-285 (Pages 12-14) discuss about Figure 8 and Table 4. However, in Table 4 under the “Fitted Polynomial Equation” column, the authors wrote “As shown in Figure 10”, but Figure 10 shows variation of Cc and Cs; and not about UCS. Did the authors mean to write Figure 8?
Author Response
Comments and Suggestions for Authors
The manuscript is about a laboratory investigation to determine the optimum soil to fly-ash mix ratio to improve the engineering properties of clayey sand for road projects. There are few suggestions/comments as follows:
- Table 2 showed that 40% Fly-ash has the highest MDD, higher than 50% Fly-ash. Also, Figure 5 showed that 50% Fly-ash has the highest UCS, higher than 40% Fly-ash. Please describe why the 40% Fly-ash despite having the highest MDD value did not obtain the highest UCS.
Response: Line 180-192 in the revised document, it has been addressed that says, “The original soil had the higher OMC than that of other mixtures. Whereas the mixture with 40% fly-ash content had the highest MDD among the original soil and the other mixtures. This could be due to the reason that poorly graded soil could have gaps in particle distributions and fly-ash particles filled the gaps establishing a great connection of soil particles due to an abundance of fly-ash particles that increased the maximum dry density up to certain percentage of fly-ash content and this process was called “Optimum Fly-ash – soil mixing ratio”. The theoretical analysis of the decreases in the MDD for 50% and 60% fly-ash content could be due the fine particles and the lightweight of Class F fly-ash comparing to the SC soil that was used in the study that was also concluded in a study by Ozdemir7 for Class C fly-ash and CL soil. Curing process could play a role here as well for the high MDD at 40% fly-ash content whereas it is supposed to be less than that of 50% and 60% fly-ash contents to maintain the trends mentioned in several studies [2, 6, 8, 16]. Beyond this fly-ash content, it led to dropping the maximum dry density, however, it was still higher than the maximum dry density of the original soil.”
- The trend lines in Figure 6, which are used to be able to get the UCS values between 8-28 days curing period, might be not appropriate. The trend lines in Figure 5 is more general than those in Figure 6. Therefore, the reviewer suggests that the authors may omit Table 3 and Figure 6, or provide related reference data.
Response: Figure 6 trend lines were used to overcome the limitations of any missing data for curing period of 2 - 8 days as well as 8 - 28 days. Therefore, the authors feel like it could be there to overcome this limitation. The other reviewers seemed to be fine with Figure 6 and Table 3. The authors would like to keep them, if possible.
- The manuscript should show or provide pictures of the “before and after” of the specimen during the UCS tests.
Response: A new (Page 7 of the revised document) Figure 5 titled “Typical specimen appearance (a) before (b) after the UCS test” has ben added to address this issue.
- Lastly, referring to wrong figure number within the manuscript brings confusion and misinterpretation to the readers. Kindly check and give the correct figure number to the following: (a) Lines 157-158 (Page 7). There is no Figure 11 in the manuscript. (b) Lines 223-253 (Pages 10-12) discuss about Figure 6 and Table 3. However, in Table 3 under the “Fitted Polynomial Equation” column, the authors wrote “As shown in Figure 8”, but the R² values matched with those in Figure 6 and not in Figure 8. Did the authors mean to write Figure 6? Kindly check also Line 225 (Page 10). (c) Lines 263-285 (Pages 12-14) discuss about Figure 8 and Table 4. However, in Table 4 under the “Fitted Polynomial Equation” column, the authors wrote “As shown in Figure 10”, but Figure 10 shows variation of Cc and Cs; and not about UCS. Did the authors mean to write Figure 8?
Response: All Figure numbers have been corrected. It was an unintentional error due to some changes made right before the submittal. Sorry for the unintentional errors.
Reviewer 2 Report
As the authors write in the paper, the objective of this dissemination is to present a laboratory investigation made to determine the optimum soil to fly-ash mix ratio to enhance the engineering properties of clayey sand that can potentially be used as a road subgrade.
The scientific level in my opinion is low. My recommendation for the authors is to try to build a process simulation model that is calibrated and validated using the data obtained by them in the laboratory. The degree of generalization of the mode can bring useful results to experts in the field, being a useful scientific research. At present, the work is useful to create a laboratory with students.
Author Response
Comments and Suggestions for Authors
As the authors write in the paper, the objective of this dissemination is to present a laboratory investigation made to determine the optimum soil to fly-ash mix ratio to enhance the engineering properties of clayey sand that can potentially be used as a road subgrade.
The scientific level in my opinion is low. My recommendation for the authors is to try to build a process simulation model that is calibrated and validated using the data obtained by them in the laboratory. The degree of generalization of the mode can bring useful results to experts in the field, being a useful scientific research. At present, the work is useful to create a laboratory with students.
Response: Thanks a lot for this suggestion. It is very important and useful suggestion to improve the use of the article. The authors feel that more data may be needed to build the model. As a result, the authors adding it as a future recommended study. In page 14, Line 359-368 of the revised document that says, “The future studies can use resilient modulus (MR) to characterize and quantify the mechanical behavior of soil materials for pavement design purposes as well as investigate the effects of seasonal moisture fluctuations which ultimately affect both their load bearing capacity and the overall performance of the materials14. The future studies can also (a) formulate and develop an enhanced hyperbolic constitutive model (eHCM) for the estimation of MR based on small-strain modulus measurements from the free-free resonant column (FFRC) test, (b) estimate MR values using the eHCM model along with FFRC test measurements, (c) calibrate and validate the eHCM model using modulus measurements obtained through conventional MR testing, and (d) finally establish statistical correlations between eHCM model parameters and routinely measured soil properties [13].”
Reviewer 3 Report
Revision needed - see attached comments (pdf file)
Comments for author File: 
Comments.pdf
Author Response
TITLE: Optimization of Soil to Fly-Ash Mix Ratio for Enhanced Engineering Properties of Clayey Sand for Subgrade Use
REVIEW COMMENTS
GENERAL COMMENTS:
- Good paper warranting acceptance consideration after addressing all of the comments below.
Response: Thanks a lot for the complement.
- English language & grammar are good – just minor improvements are needed throughout the paper.
Response: Thanks a lot. The corrections have been done.
- Paper is thorough and easy to comprehend.
Response: Thanks a lot for the complement.
4) The paper should have a Section 4 entitled “Conclusions and Recommendations” where future recommendations on the basis of limitation of the study should be suggested.
Response: Thanks a lot for this suggestion. Section 4 title has been changed to “Conclusions and Recommendations” along with 2 subsections 4.1 Conclusions and 4.2 Recommendations for Future Studies. Provided in pages 13-14, Line 328-368 of the revised document.
5) “enhanced engineering properties” could be omitted from keywords.
Response: this keyword has been changed to “engineering properties” as the study was focused on engineering properties of soil.
6) Usage of 40%, 50%, and 60% fly-ash should be justified with proper references.
Response: A statement in pages 3-4, Line 110-114 has been added to justify the percentages of fly-ash used in the study that says, “ The percentages of fly-ash (0%, 40%, 50%, and 60%) in the soil-fly-ash mixtures and the curing periods (0, 2, 8, and 28 days) were arbitrarily selected for the experiments. Higher percentages of fly-ash was selected to find the highest optimum fly-ash to maximize the beneficial use because most of the studies conducted used highest fly-ash content of 20% except for one where the maximum fly-ash content used was 40%.”
7) Advanced Statistical Analysis could be done in order to generate more accurate results and provide additional scientific merit to the paper.
Response: That seems to be a good suggestion. The authors thought about it and could not figure it out what kind of appropriate advanced statistical analysis can be done.
8) Figure references throughout the paper are misspelled.
Response: All Figure numbers have been corrected. It was an unintentional error due to some changes made right before the submittal. Sorry for the unintentional errors.
ABSTRACT:
9) Page 1, Line 15-16: Grain size distribution, Atterberg limits, Proctor compaction, unconfined compression, and the consolidation tests were conducted.
Response: This sentence has been deleted as it seems to be duplicate information and it does not bring any additional information.
10) Page 1, Line 25: The settlement and the volume change behavior improved with increased fly-ash content. (Quantifiable data can be provided from the results)
Response: A quantifiable data that says, “The settlement and the volume change behavior improved at least 44% with increased fly-ash content.” is provided in Line 25-26 in the revised document.
11) Optimum moisture content, Maximum dry density, and Unconfined Compressive Strength can be added to the keywords.
Response: These terms have been added in the keywords as suggested (Lines 27-28 in the revised document).
INTRODUCTION:
12) Page 2, Line 44-45: The term “Soil Stabilization” refers to the modification of soil through the utilization of additives to enhance the engineering properties.
Response: This sentence has been deleted as it seems to be redundant here.
13) Page 2, Line 45-46: Fly-ash has been used as a soil stabilizer in the highway and transportation industry in different layers and different methods. (A table summarizing uses of fly-ash in soil can be provided)
Response: The authors looked for more publications to summarize the use of fly-ash in a tabular form. But they were not that successful to find a lot specially in TRR and TRB publications. So, putting in a tabular form of the information may be incomplete and misleading to some extent. As a result, the authors decided not to summarize in a table form. Based on the suggestions from the editor and you (in the comment 15) authors found couple of related publications from TRR and TRB and included in the literature review [13, 14].
14) Page 2, Line 46-47: Fly-ash has also been used to increase the stability of road roads embankments by strengthening soft subgrade soil.
Response: The authors did not understand this comment as it is directly copied from the manuscript without mentioning as to what to do.
15) Line 44-73: The text discussions here should be supplemented, substantiated, & populated by citing the following two references: (a) https://doi.org/10.1080/14680629.2020.1756901 ; and (b) https://doi.org/10.1177%2F0361198119833681
Response: The authors did review these two references and used them in appropriate places [13, 14] as they fit. Thanks for the links.
16) Page 2, Line 56-58: White et al. [5] studied the short- and long-term behavior of the soil treated with fly-ash content of 5%, 10%, 15%, and 20%.
Response: The authors did not understand this comment as it is directly copied from the manuscript without mentioning as to what to do.
17) Page 3, Line 69-73: This study performed compaction tests according to Method A of ASTM D1557 and concluded that as the fly-ash content in the mixture increases the MDD decreases, the theoretical analysis of the decrease decreases in the MDD is because the fine particles and the lightweight of Class C fly-ash compared comparing to the CL soil that was used in the study.
Response: The authors did not understand this comment as it is directly copied from the manuscript without mentioning as to what to do.
MATERIALS AND METHODS:
18) Page 4, Line 106: Figure for soil samples could also be included.
Response: A figure of soil sample has been included in Figure 1 (1c)
19) Page 5, Figure 2: Experimental method is misspelled in the figure.
Response: Corrected. Sorry for the unintentional error.
20) Page 7, Line 157-158: Figure 9 is misspelled as Figure 11.
Response: Corrected. Sorry for the unintentional error.
RESULTS AND DISCUSSIONS:
21) Page 8, Table 2: The anomaly for increase of OMC at 50% fly-ash-soil should be addressed too.
Response: Part of the paragraph, Lines 185-191 in the revised document has been updated to address this issue that says, “The theoretical analysis of the decreases in the MDD for 50% and 60% fly-ash content could be due the fine particles and the lightweight of Class F fly-ash comparing to the SC soil that was used in the study that was also concluded in a study by Ozdemir [7] for Class C fly-ash and CL soil. Curing process could play a role here as well for the high MDD at 40% fly-ash content whereas it is supposed to be less than that of 50% and 60% fly-ash contents to maintain the trends mentioned in several studies [2],[6],[8],[16]. Beyond this fly-ash content, it led to dropping the maximum dry density, however, it was still higher than the maximum dry density of the original soil.”
22) Page 9, Line 196: Specify the optimum moisture content used.
Response: This sentence has been updated to indicated that the mixtures were compacted at respective optimum moisture contents (Table 2) that is presented in Table 2. Line 196-197 in the revised document.
23) Page 9, Line 207-209: Scanning electron microscope can be used to clarify. 2 | 2
Response: Our University is primarily a teaching university that became R2 in 2019 due to the elimination of R3. Currently, we do not have lab equipment, such as SEM to do this kind of analysis.
24) Page 9, Line 216-218: The decrease decreases in the UCS could also be attributed to the changes in outside humidity, since the samples were kept in the lab and the indoor temperature and humidity are related to outdoor factors. ( Future recommendations on this limitation needs to be addressed)
Response: A future suggested study has been included in Lines 354-357 in the revised document that says, “The decrease in the UCS seems to be attributed to the changes in outside humidity, since the samples were kept in the lab and the indoor temperature and humidity are related to outdoor factors. Future studies can be performed to simulate the outdoor conditions to eliminate this limitation.”
25) Page 9, Line 218-219: The optimum curing period seemed to be 8 days because zero to very little increase in of strengths was observed after this period (Figure 5).
Response: This sentence has been updated that says, “The optimum curing period seemed to be 8 days because no increase of strengths was observed and some cases a decrease of strengths was observed after this period (Figure 5)” to clarify the issue. Provided in lines 220-222 in the revised document.
26) Page 10, Line 225: Figure 6 is misspelled as Figure 8.
Response: Corrected. Sorry for the unintentional error.
27) Page 10, Line 236-241: The paragraph can be included in the literature review section of the paper.
Response: The authors feel like this does not belong to the literature as it does not have direct relationship with the article theme. It is an analysis tool and related to the analysis that was done to address the limitation of the data.
28) Page 11, Table 3: Figure 6 is misspelled as Figure 8.
Response: Corrected. Sorry for the unintentional error.
29) Page 13, Table 4: Figure 8 is misspelled as Figure 10.
Response: Corrected. Sorry for the unintentional error.
CONCLUSIONS:
30) Page 17, Line 354-356: Potentially 32% - 50% of fly-ash can be used beneficially as a beneficial use that would otherwise go to landfill to be managed.
Response: The authors did not understand this comment as it is directly copied from the manuscript without mentioning as to what to do.
REFERENCES:
31) References should be updated accordingly – refer to Comment# 14 above.
Response: The authors did review these two references (13 and 14 in the revised document) and used them in appropriate places as they fit.
32) Reference citation & listing formats should be rechecked for consistency with the journal.
Response: The citations and references were updated using Zotero for ACS/IEEE format.
33) Overall, good paper warranting acceptance consideration after addressing all of the above comments.
Response: Thanks a lot. It means a lot to us.
Round 2
Reviewer 2 Report
The authors have improved the paper in relation to some of my observations. I am waiting for future papers to be able to see the recommended model.
Reviewer 3 Report
Authors have addressed all of this Reviewer's comments.
The revised manuscript should be accepted.
