Mechanical and Self-Healing Performance of Yellow River Alluvial Silt Treated with Composite Flexible Curing Agent

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

 This article investigated stabilized Yellow River alluvial silt's mechanical properties with a flexible composite curing agent. The article requires some revision and the comments are listed below.

1. Line 1 “This report presents” I suggest using the sentences “This article or research presents”.
2. Abstract, the description of the work investigated is unclear and should be improved with more detail.
3. Most of the literatures were cited in a group. However, more individual literatures regarding compressive strength, drying shrinkage, freeze-thaw and high temperature should be discussed in the introduction section.
4. Line 149, Add the properties of Portland cement, sintered mud and asphalt powder.
5. Line 163, Why is the cement content limited to 5%? Highlight this in the manuscript.
6. Line 163, on what basis the 2%, 4%, 6%, 8% flexible curing agents were selected? Why is it limited to 8%?
7. Table 2, why is the standard curing compressive strength higher than the immersion curing?. The reason should be discussed in section 3.1.
8. Compressive strength results, section 3.2-3.4 results can be compared with earlier findings. Results correlation can further improve the reliability of the investigation.
9. Figure 7, calcium silicate hydrate gel, flaky calcium hydroxide and acicular ettringite should be marked or shown in the figure for better understanding.
10. Conclusions should be improved. Quantify the results and include the key findings.

Author Response

1- Line 1 “This report presents” I suggest using the sentences “This article or research presents”.

Response: Thank you for your suggestion, we have made corresponding modification in red words.

2-Abstract, the description of the work investigated is unclear and should be improved with more detail.

Response: Thank you for your suggestion, we have improved the abstract and made corresponding modification in red words.

3-Most of the literatures were cited in a group. However, more individual literatures regarding compressive strength, drying shrinkage, freeze-thaw and high temperature should be discussed in the introduction section.

Response: Thank you for your suggestion, we have improved the introduction section and made corresponding modification in red words.

4-Line 149, Add the properties of Portland cement, sintered mud and asphalt powder.

Response: Thank you for your suggestion, the properties of Portland cement, sintered mud and asphalt powder have been added in table 2-4 and corresponding modification has been made in red words.

5-Line 163, Why is the cement content limited to 5%? Highlight this in the manuscript.

Response: We are very sorry for our unclear report in designing of the cement content. The design of the cement content is based on the engineering experience and previous study results. In China, the cement content in the cement-solidified soil for engineering is mostly 4%-6%, the cement content of 5% is selected as the reference group for the experimental comparison in this paper.

Corresponding modifications have been made in the revised manuscript in red words in 2.2 according to the reviewer’s comments.

6-Line 163, on what basis the 2%, 4%, 6%, 8% flexible curing agents were selected? Why is it limited to 8%?

Response: The design results are based on a large number of tests. Initially, based on the research experience and some literatures on solidified soil, 5%,10% and 15% flexible curing agents was selected in initial research and the compressive strength was taken as the evaluation parameter of stabilization effect. The results showed that the strength of the solidified silt with 10% content decreased significantly compared with that of 5% content. Then, the 2%, 4%, 6%, 8%,10% flexible curing agents were selected in next research. The addition of 8% flexible curing agents causes decrease in compressive strength compared with that of 6% flexible curing agents. This phenomenon is attributed to plasticity enhancement with the increase of asphalt content. Therefore, it is limited to 8% flexible curing agents in this paper considering the influence of asphalt content.

7-Table 2, why is the standard curing compressive strength higher than the immersion curing?. The reason should be discussed in section 3.1.

Response: The standard curing compressive strength is higher than the immersion curing. Some researchers also reported the same conclusion (Fan, 2019 and 2021).

The composite flexible curing agent was prepared by sintering red mud and asphalt as the main raw materials. The sintered red mud contains active CaO and SiO2 and has hydration activity. Under standard curing conditions, the cement and red mud in curing agent undergoes hydration reaction to form C-S-H and other products. Moreover, the asphalt particles connect the hydration products and silt particles under the action of physical compaction. However, when the sample is soaked in water, the internal structure of the solidified silt is destroyed, the gel material is peeled off from the soil particles, and the number of pores in the sample increases. As a result, the compressive strength of sample under standard curing condition is higher than that of sample under the immersion curing condition.

Some improvements were made in the article and the reference was added accordingly.

Liang Fan, Shanwei Mou，Yong zhen Li. Strength and Water Stability of Compound Stabilized Silt with Emulsified Asphalt. Highway Engineering, 2019,44(4): 178-238

Liang Fan, Sheng-jie Zhou, Jia-lin Hou, Lin Wang. Composite Stabilization of Silty Soil near the Yellow River: Two Methods and Performance Comparison. Journal of Yangtze River Scientific Research Institute, 2021,38(12):118-124.

8-Compressive strength results, section 3.2-3.4 results can be compared with earlier findings. Results correlation can further improve the reliability of the investigation.

Response: Thank you for your suggestion. We have made corresponding modification in section 3.2-3.4, and the earlier findings was compared.

9-Figure 7, calcium silicate hydrate gel, flaky calcium hydroxide and acicular ettringite should be marked or shown in the figure for better understanding.

Response: Thank you for your suggestion. Calcium silicate hydrate gel, flaky calcium hydroxide and acicular ettringite are marked in Figure.7.

10-Conclusions should be improved. Quantify the results and include the key findings.

Response: Thank you for your suggestion. The conclusions has been rewritten to be more concise.

Reviewer 2 Report

This review report has been removed from the review record as it did not meet MDPI’s review report standards.

Reviewer 3 Report

Comments and Suggestions for Authors

This paper presented a study regarding the effect of composite flexible curing agent on aged mechanical properties of treated ilt, in which the replacement levels of the flexible curing agent below 10% by weight are compared. This work introduces new findngs with repsect to the flexible curing agent in cementitious composites. This paper is well written and is in the journal scope. Therefore it is worthy to consider this paper for publication. Hovewer, major revision shoud be introduced into the manuscript. The comments of this paper are as follows:

(1) Keywords. Keywords must indicate the main materials, tests, and methodology used in the study. Therefore, it is required to revise the keywords, add new one, and write based on the points mentioned above.

(2) Abstract. Abstract need to be rewritten to report about the main and new findings obtained in this paper briefly.

(3) Topic selection and literature review. The article concerns the analysis of mechnaical and rheological  parameters of composites strenghthening by specific curing agent. This issue should be developed. Furthermore, new curing and nucleating agent materials using in new composites should also be described. Therefore at least, below paper from MDPI database should be discussed and cited in the manuscript:

- "Rheology of cement pastes with siliceous fly ash and the csh nano-admixture”, Materials 2021.

(4) Experiments. Please introduce the name of SEM equipment used in the studies.

(5) Tests. Please provide photos showing specimen during mixing, casting, curing, testing etc. This section should be enlarged and contains relevant photos from the conducted experiments.

(6) Results. Presentation of test results should be shown in different colors. Moreover results on graphs should contain error bars.

(7) Conclusions. Please condense the conclusion part and emphaize the main innovaltive findings.

Author Response

Special thanks to you for your good comments. We have carefully revised the manuscript, and the paper was also re-scrutinized to improve the English. Our responses are as follows, and we amended the relevant part in revised manuscript and the changes below are noted in red words in the article.

1-Keywords. Keywords must indicate the main materials, tests, and methodology used in the study. Therefore, it is required to revise the keywords, add new one, and write based on the points mentioned above.

Response: Thank you for the suggestion. We carefully checked the keywords and confirmed that the keywords in the manuscript can indicate the points mentioned above.

2-Abstract. Abstract need to be rewritten to report about the main and new findings obtained in this paper briefly.

Response: Thank you for the suggestion. we have improved the abstract and made corresponding modification in red words.

3-Topic selection and literature review. The article concerns the analysis of mechnaical and rheological  parameters of composites strenghthening by specific curing agent. This issue should be developed. Furthermore, new curing and nucleating agent materials using in new composites should also be described. Therefore at least, below paper from MDPI database should be discussed and cited in the manuscript:

- "Rheology of cement pastes with siliceous fly ash and the csh nano-admixture”, Materials 2021.

Response: Thank you for the suggestion. We have made increase discussion about the analysis of road performance properties of composite curing agent. And the materials using in new composites were described in 2.1 section.

The composite flexible curing agent was developed with sintered red mud and No. 70 base asphalt as the main materials. First, the sintered red mud was dried and ground to less than 120 mesh for use. Then, the base asphalt was heated to a certain temperature and the ground sintered red mud was put into in proportion. After fully stirring for 120s, it was cooled to room temperature. Finally, an appropriate amount of dispersant was put in, and the mixture was crushed to less than 0.075 mm with a pulverizer to obtain the composite flexible curing agent.

The paper concerns the road performance of stabilized silt soil rather than the cement paste. After careful discussion, we think that the paper you mentioned is not suitable for citation in this article.

4-Experiments. Please introduce the name of SEM equipment used in the studies.

Response: The name of SEM equipment used in the study is ZEISS Sigma 500. It has been mentioned in 2.3.5 section.

5-Tests. Please provide photos showing specimen during mixing, casting, curing, testing etc. This section should be enlarged and contains relevant photos from the conducted experiments.

Response: Special Thanks for your suggestion. The relevant photos of experiments are as follows. After careful discussion, we believe that the mixing, casting, curing, and performance testing of the samples are all routine operations according to standards, and there is nothing special, so there is no need to put all the photos in the article.

Specimen casting by static pressure method

  The curing of samples      

 compressive strength test

 Test piece and shrinkage meter

Soil sample state after low temperature freeze-thaw

6-Results. Presentation of test results should be shown in different colors. Moreover results on graphs should contain error bars.

Response: Special Thanks for your suggestion. The figures has been modified to show in different colors, and the error bars was also added in related figures.

7-Conclusions. Please condense the conclusion part and emphaize the main innovaltive findings.

Response: Thank you for your suggestion. The conclusions has been rewritten to be more concise.

Author Response File: Author Response.docx

Reviewer 4 Report

Comments and Suggestions for Authors

The conducted work “Mechanical Behavior of Yellow River Alluvial Silt Treated with Composite Flexible Curing Agent” is good. However, following comments should be addressed to further improve paper:

1. Add more recent relevant literature review from 2021 and 2022 in introduction section. Also, explicitly mention the novelty and research significance of current work in last paragraph of introduction section.
2. Avoid long sentences throughout the manuscript, e.g. lines 226-231, etc.
3. Show standard deviation where average is being taken.
4. Outcome should be further discussed in detail. More scientific reasoning emphasis is required while elaborating outcome.
5. There should be a separate section (before conclusions section) explaining the implementation of this research in real field for practicing professionals.
6. Closing remarks should be added at the end of conclusion section keeping in mind all conclusive bullet points.
7. English Language should be improved throughout the manuscript.

Author Response

I am very grateful to your comments for the manuscript. According with your advice, we amended the relevant part in manuscript. Your questions were answered below, and the changes are noted in red words in the article.

1-Add more recent relevant literature review from 2021 and 2022 in introduction section. Also, explicitly mention the novelty and research significance of current work in last paragraph of introduction section.

Response: Thank you for your suggestion, we have improved the introduction section and made corresponding modification in red words.

Researchers have carried out a lot of experimental research and practical work on the solidification and stabilization materials of silt, and have achieved good theoretical analysis and experimental results. The solidified materials have gradually developed from traditional inorganic and organic types to inorganic-organic composite and biological improvement cured. However, there are still problems of single improvement effect and high technical difficulty in popularization and application of silt solidification in engineering application practice. And research on self-repair is relatively lacking Therefore, it is very necessary to further study the changes of the road performance of the solidified silt under the unfavorable conditions of actual work, such as water, temperature and natural or load effects, on the basis of the basic performance research on the strength and deformation of the solidified silt.

Sintered red mud is a solid industrial waste residue discharged from the production of alumina by the alkaline process. It has high calcium oxide and silicon oxide content, small particles and a network structure inside, which has strong adsorption capacity and certain hydration activity. Asphalt is a complex mixture of hydrocarbons and their derivatives with different molecular weights. It is a temperature-sensitive material with flow self-healing properties. Combined with the characteristics of sintered red mud particles and asphalt materials, the two materials were mixed and ground under a certain process to prepare a new type of silt curing agent, and the silt was solidified and stabilized through physical-chemical comprehensive action. The preparation process of the new curing agent can realize the value-added utilization of industrial solid waste - sintered red mud, and at the same time convert asphalt into solid powder form at normal temperature, which is beneficial to the engineering practice and construction quality control of solidified silt.

On the basis of evaluating the basic mechanical properties of the composite flexible curing agent stabilized silt, the mechanical properties of stabilized silt under test conditions such as water softening, cyclic heating, low temperature freeze-thaw, and high temperature self-healing were further studied, and the effect of the composite flexible curing agent content on water stability of stabilized silt, frost resistance and damage repair performance was analyzed. Scanning electron microscope (SEM) was used to observe the microscopic morphology of silt, cement stabilized silt and the composite flexible curing agent stabilized silt, respectively, to analyze the influence of different materials on soil structure and pore characteristics, and to explore the mechanism of solidification and stability.

2-Avoid long sentences throughout the manuscript, e.g. lines 226-231, etc.

Response: Special thanks for your good comments. We have carefully revised the term in the manuscript and modified long sentences. Corresponding modification was made in red words.

3-Show standard deviation where average is being taken.

Response: Thank you for your suggestion. The error bars has been added in related test results. Corresponding modification was made in red words.

4-Outcome should be further discussed in detail. More scientific reasoning emphasis is required while elaborating outcome.

Response: Thank you for your suggestion. The previous related researches have been added to increase the discussion in Section 3. Corresponding modification was made in red words.

5-There should be a separate section (before conclusions section) explaining the implementation of this research in real field for practicing professionals.

Response: Special thanks for your suggestion. This paper mainly discusses the road performance laboratory test and result analysis of flexible solidified silt. There are many differences between the test indicators and methods of specific project implementation in real field and laboratory tests. We will write another paper to discuss in detail.

6-Closing remarks should be added at the end of conclusion section keeping in mind all conclusive bullet points.

Response: Thank you for your suggestion. The conclusions has been rewritten to be more concise. And the study and future research topics was added at the end of conclusion section

7-English Language should be improved throughout the manuscript.

Response: Special thanks to you for your good suggestion. We have carefully revised the manuscript, and the paper was re-scrutinized to improve the English. Corresponding modification was made in red words.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

All comments are addressed sufficiently.

Reviewer 3 Report

Comments and Suggestions for Authors

I have no comments.