Study on Mechanical Properties and Constitutive Equation of Earth Materials under Uniaxial Compression
Round 1
Reviewer 1 Report
The proposed paper investigates the uniaxial compressive mechanical properties of earth materials by experimental tests. The theme is interesting. In my opinion the following topics should be improved.
The compressive strength of the tested material is rather low (2-3 MPa). So the practical application of this material in structural or nonstructural fields should be better described, also providing suitable references on this aspect.
Due to the particular nature of the material (earth material), additionals properties should be investigated dealing with durability. This concept should be mentioned in the paper. The authors could refer to the following study:
Fiore A., Marano G.C., Marti C., Molfetta M. (2014), “On the fresh/hardened properties of cement composites incorporating rubber particles from recycled tires”, Advances in Civil Engineering, Vol. 2014, Article ID 876158, 12 pages, ISSN: 1687-8086, DOI: 10.1155/2014/876158.
The experimental procedure should be described in detail.
Finally I propose a careful reading of the work to eliminate typing and language errors.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Dear Authors,
I propose to review and complete the citations in the content. There are no references given to items 4, 19, 20, 21, 22 and 23. The numbering of the Tables should be corrected.
I suggest you describe the soils better. The results of the studied dependence will be different depending on the humidity of the samples, their density, mineral composition, etc. The place where the soil comes from is not a physical quantity such as a precise graining curve. It is not sufficient to indicate the type of soil. The soil moisture content seems to be too high – such soil should not be used for earth building material.
To conclude that 28-day curing period is the best , it is necessary to add information on how they were seasoned (humidity, temperature) and check what results would be obtained for the samples after a seasoning time longer than 28 days. The strength of earthen building materials continues to increase intensively after 28 days.
Moreover, comparing your results with the research of other scientists much more data about of the soil used by you and by others is required. Also you suggest that other researchers used soil with more humus (line 319). Soil with any organic matter cannot be used in such research and generally in soil mixtures used for earth building materials.
You compare your results mostly with thesis of other authors. These thesis cannot be easily find for other researchers (they are not published anywhere). Therefore more information should be shown In your manuscript.
Author Response
Please see the attachment
Author Response File: Author Response.docx
Reviewer 3 Report
1. In lines 83-85 it is necessary to briefly mention some bibliographic example of the mentioned methods.
2. In the discussion of Figure 1 it is necessary to indicate the type of material according to the USCS (Unified Soil Classification System) classification.
3. In Table 2, explain the meaning of the symbol Φ present in column 2.
4. Different curing times are mentioned but there is no explanation of the method used or why to apply such curing. Was any stabilizer used?
5. Why is Poisson's modulus data not included?
6. Equation 4 is mentioned on line 267 but only two equations are identified in the document.
7. In the discussion of lines 312-320 add the USCS classification of the materials mentioned.
Author Response
Response to Reviewer 3 Comments
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The authors answered all points. The paper can be published in the present form.
Author Response
非常感谢您对本文的帮助，我们最真诚地感谢您。
Author Response File: Author Response.docx
Reviewer 2 Report
Dear Authors,
Thank you for responding to my comments and supplementing the article with grain size and mineral composition. Although you have completed the work with these key parameters, I doubt their credibility. The specimens were prepared and tested some ime ago. I question that you have mesured mineral composition and grain size measurements on the soil used to form the test samples. Although it is also unlikely, even if you managed to examine the missing variables in just a few days that you had to prepare your response to the review, they were made on a different soil, at most from the same region. However, as the research results you publish in Table 5 show, for the Xinjiang region, individual soils were characterized by significantly different properties. Also, the reviewer's experience shows that it cannot be assumed that the soil on is similar in the area. Therefore, a mistake was made in the preparation of the experiment without examining the essential characteristics of the soil used.
The reviewer was not given enough time to reach all the new literature items listed (especially the above MA theses), but he decided to verify some of them. And so, referring to the well-known article [4] Van Damme, H.; Houben, H.; Earth concrete. Stabilization revisited. Cement. Concrete. res. 2018, 114, 90-102.
Autors write:
„According to statistics, about 30% of the world's population still lives in houses built of earth materials. The low strength of earth materials (compressive strength 1Mpa-3MPa) makes them mostly used in low-rise buildings with 1-3 floors (vertical compressive stress of 0.1Mpa-0.3MPa) [4]”
In the cited reference there is no information that earth materials are mostly used in 1-3 storey buildings. There is also no compressive strength range of 1Mpa-3MPa for earthen materials. Houben et. all states: "The unconfined compressive strength of unstabilized earth goes from a few tenths of MPa for air dried earth (~0.5 to ~1.5 MPa for cob; ~1.0 to ~2.5 MPa for adobe) to a few MPa for rammed earth (~ 1. to ~4. MPa) and compressed blocks (~1 to ~7 MPa)”
Then the authors state that "nearly 60 million people live in earth buildings", which is not true, it is about 100 million people.
The authors in line 136-138 state that the mineral composition of the soil is dominated by common minerals such as quartzite and calcite. Nothing else was mentioned about minerals. I don't know what the mineral composition of the clay is which is essential. We know that there are clay minerals in clay such as illite, kaolinite, beidelite, montmorillonite, etc. Depending on what clay materials are present in the soil, we can expect significantly different optimal moisture content (OMC). Quartz and calcite are minerals found mainly in the silt and sand fraction of the soil and this is not the information the readers of the article (manuscript) care about.
The authors in line 168-181 state according to which standards they prepared cubic specimens. Each size and shape was formed differently according to Mexican, Chinese or New Zealand standards. Each standard includes a different method of forming samples (different: compaction energy, ramming number, method of ramming, etc.). Then, in lines 181-206, one method is given, similar to the one described in one of the standards.
The authors provide the values of the determined optimum moisture content, but without specifying the method by which it was determined. The Optimum moisture content (OMC) is the moisture content at which the soil attains maximum dry density. This OMC value is with respect to the specific amount of compaction energy applied to the soil. The authors in the revised text state that the specimens were compacted in three layers with a compaction work of 592,188 kj/m3 and 25 strokes per layer. Has an OMC been designated for this method? OMC can be measured by mainly two methods Standard Proctor Compaction Test and Modified Proctor Compaction Test. The authors also compare their OMC values in Table 5 to the works of a series of master's and doctoral theses from 2017 [34,36,39,40]. There, the samples seems to be shaped and compacted differently. In this way, the reader is misled during the analysis of Table 5.
The authors write that the samples were compacted in three layers. The specimens shown in Figures 3, 4 and 5 appear to be molded in a single layer. In line 204 the authors state that:
"the average dry density of the specimens at 28 d was 1.61g cm-3, indicating that the specimens had basically hardened". The specimens compacted in three layers with a compaction work of 592 kJ/m3 and 25 strokes per layer for samples of different sizes will be significantly different. In addition, for the given particle size curve, the obtained density of 1.61g·cm-3 is too low, if, as the authors write, the composition of the soil was 19% clay particles. In Table 5 for samples from other publications much higher densities were obtained with similar OMC.
In response to the review, the authors write:
". We measured the moisture content and strength of the earth specimens at 14d, 21d, 28d, and 56d with this method of curing, and found that the water contents of the specimens at 14d, 21d, 28d, and 56d were 8.8%, 4.3% , 3.5%, and 3.2%. Respectively, while the measured strength values were 1.81MPa, 2.33MPa, 3.05MPa, and 3.31MPa. After 28 d, the strength and moisture content increased rather slowly. Therefore, we consider that the raw soil specimens with a curing age of 28 d are fully cured under the premise of the curing conditions used in this test”
Why is this information not in the text of the article?
Author Response
非常感谢您的宝贵意见，我们根据您的意见对论文进行了修改。我们感受到你们在修改过程中的认真和细致。因为您的帮助，我们的文章会得到更多的改进。最真诚地感谢你。
Author Response File: Author Response.docx
Round 3
Reviewer 2 Report
Dear Authors,
Thank you for completing the text of the article and taking my suggestions into account.
Regards,
