Strength and Deformation Characteristics of Dune Sand Earth Blocks Reinforced with Natural and Polymeric Fibers

Round 1

Reviewer 1 Report

Abstract

1. Expand GCC when used for first time
2. p.1, line 11 - several mixes - specify the number of mixes used in the study
3. Reconsider choice of keywords, particularly "improved soil"

Introduction

4. Authors can consider including literature section in the introduction and the summary of the work can be given at the end of this modified introduction and emphasis its contribution
5. The section on literature review and summary can be concise without excluding any of the referred works

Earth Block Materials and Experimental Programme

6. The data on the geotechnical properties of the soil and the gradation analysis can be represented as a single table for the different type of soil used
7. What compaction technique was adopted for dune sand? What is the percentage of fines in dune sand?
8. The properties of all the three fibres can be consolidated in a single table.
9. What is the length and diameter of the fibres used for block making?
10. How was the percentage of fibres fixed as 0.25, 0.5, 0.75 and 1 %?
11. Were the blocks moulded at the OMC? What about dune sand?
12. Test set-up for the compression test conducted in the study must be included.

Results and Discussion

13. Please name fibres based on the manufacturer specification or material instead of black or white
14. Minimum three blocks are required for each mix
15. 10, line 371- How can CBR be conducted on blocks?
16. Figure 7, does it show the stress-strain curve from UCC test or the compression test (3-point test) on blocks?
17. 14, lines 447-459 – the poor performance can be due to fibre clumping that happens when there is improper mixing. Have authors considered this fact? Also, if authors conclude that fibre (I presume synthetic) does not improve block strength, they should compare it with available literature to justify the trend. Many literatures show good improvement in strength. Also, please be specific of fibre type in this section. It is a very confused presentation.
18. Figure 10, Can authors explain the abrupt 1% stress-strain curve?
19. Figure 11 – did authors get the stress-strain curve from this set-up? How was deflection measured? Please explain.
20. p.17, line 538 - How CBR was used to assess compressive strength
21. How did authors arrive at 0.5% cement content? 
22. The results and discussion section must be restructured for better understanding and clarity to the readers. 
23. The method of test used for assessing compressive strength is not clearly mentioned and raises a lot of questions about the validity of the results
24. Error bars to be included in all the graphs showing compressive strength
25. Photos of blocks at failure showing the fibre bridging can be added to supplement the results

Author Response

Please check the attached file.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors have made all the required corrections.

Author Response

Please check the attached file.

Author Response File: Author Response.pdf

Reviewer 3 Report

1) The compaction curve of pure sand in Fig.2a could not be this kind of single peack curve. The maximum dry density of pure sand could be test with relative density method.

2) The compressive strength of the blocks is related to the water contents of the mixed soil. The mold procedure is not corresponding to the compaction test, So the water content of molding blocks should not be the  optimum moisture content.

Author Response

Please check the attached file.

Author Response File: Author Response.pdf

Reviewer 4 Report

Very interesting article. I have a few questions and comments:

1. Have you tested the effect of fibers on the optimum moisture content (Proctor compaction test) of the mixture (i.e. clay + sand + different fiber and + cement)? I think this can be more important for blocks with natural palm fibers and natural fibers and cement because of water absorbing. I think optimum water content value will be grater.
2. When presenting the properties of synthetic fiber, they were not given properties for white fiber, only for black fiber (table 1b)?
3. Is it possible to determine the density after block preparation, before drying? Static compaction for that was used, but preliminary compaction tests were done by dynamic compaction test. This could be (density after static compaction) compared to the Proctor results. Perhaps, as a result of static compaction, we obtain lower sample densities and lower strength and stiffness.
4. Was the number of tests not influenced on the results? I. If tests (for samples with the addition of fibers) were performed only for one sample, the results may be distorted, e.g. look on results of stiffness of blocks stabilized with 0.75% natural fiber, block with 0.25% white fiber r. I think at least 3 tests are needed for each type of earth block.
5. In tests for earth blocks, the stiffness was obtained as for good soils (i.e. medium dense sand), E50 = 80-100 MPa. But, is it enough for the walls? Will not be their deformation too high?
6. Figure 2 – I think density in g/cm³ will be better.
7. Line 496-511 – mistake in text (number of figure)– Figure 12 instead Figure 11.

 

Author Response

Please check the attached file.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have revised the manuscript based on the suggestions

1. Table 1 in p.5, section 3.1. Authors are requested to provide properties of both soil used for study. 
2. Legend box in figure 12a to be placed properly
3. CBR is conducted on soils compacted with light compaction test. I assume authors are referring to the same as cylindrical samples. 

Author Response

in attached file

Author Response File: Author Response.pdf

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Comments in attached file

Comments for author File: Comments.pdf

Reviewer 2 Report

1. Please change "casted" to "cast" in the abstract and other mentioned places.
2. At the end of the introduction section, authors are requested to highlight the uniqueness of their work from other such literature.
3. Summary of work presented at the end of introduction is not adequate. It should emphasize the need for the study also.
4. Section 2 literature review is inadequate and does not report the newer literature on the subject
5. Also, the structure of literature review must be changed to suit readership. It should compare the various aspects like different types of fibres, their proportion, cement content, size of block, etc. of various authors instead on reporting a summary of work of each literature. This limits the literature review.
6. Authors are requested to combine introduction and literature review section with a summary on research gap identified and how their work addresses it.
7. Authors are requested to check the specific gravity of clayey silt. It should be around 2.7. This value is low.
8. The justification for choice of fibre can be moved to the introduction section instead of section 3.
9. Section 3.1: mention the average diameter and length of the fibres.
10. Section 3.2: What is the size of the blocks?
11. Section 3.2: What is the fibre content and the cement content?
12. Figure 5 appears generic. Mention which blocks showed strain hardening behaviour and strain softening behaviour.
13. Figure 6 Why 12% clay content shows higher resistance than 10.8%
14. Section 4.2 - refer to fibre with its type or name instead of colur. 
15. Figure 9: Why has the curve been truncated (1%)
16. Why the performance dips at lower fibre content for polymeric fibre?
17. Figure 13: Curve of palm fibre is truncated. Why?
18. The discussion section must be improved significantly. The paper has considered only strength? What about durability of the block or its resistance to wearing?
19. What are the limitations of the study?
20. Microscopic images of fibres can be included to discuss the nature of fibres and their effect on strength of the blocks
21. Conclusion should be brief highlighting the findings of the study and its limitations.
22. Authors can consider including the following reference: Evangelin Ramani Sujatha and Selsia Devi S (2018) Reinforced Soil Blocks: Viable Option for Low-Cost Building Units. Construction and Building Materials. 189:1124-1133.