An Approach to Understanding the Hydration of Cement-Based Composites Reinforced with Untreated Natural Fibers

Round 1

Reviewer 1 Report

I strongly do not agree with the way TGA data was analyzed in this manuscript. The author's method was referred to an rather old piece of reference. For a better data analysis method please find the following literature:

 T Kim, J Olek. Effects of sample preparation and interpretation of thermogravimetric curves on calcium hydroxide in hydrated pastes and mortars. Transportation research record 2290 (1), 10-18

We, along with many other researchers have tried, but “untreated” natural fiber does not work in cement-based materials, hence its influence on hydration does not mean much…

Author Response

The authors would like to thank the contribution of the reviewer for their thorough examination of the manuscript and valuable comments, which will undoubtedly enhance the manuscript’s quality.

The authors’ response to the reviewer’s suggestions are attached.

Author Response File: Author Response.pdf

Reviewer 2 Report

Paper ID: sustainability-2331715

Type:Article
Title: An approach to understanding the hydration of cement-based composites reinforced with untreated natural fibers

Authors: Joan Llorens , Fernando Julián , Ester Gifra , Francesc X. Espinach , Jordi Soler , Miquel Àngel Chamorro

 

This paper investigates untreated natural fibers on the hydration process of cement Portland composites. Although the testing methods and compared results attained in the present study show the importance of the paper, this paper needs extensive revision.

1.     ……. “materials as metakaolin, crushed waste calcined clay bricks ground granulated blast furnace slag, calcined waste crushed clay bricks, with a promising results [19–26]” . Each one of the cited references must be discussed individually and demonstrate their significance to your work. Not [19-26], should be [19] text what is presented in the manuscript [20] text what is presented in the manuscript [21].

2.     Novelty in comparison to recent literature? “What is new? Please give it in the last paragraph of Introduction section. Delete the main conclusions given in the last paragraph of the Introduction section.

3.     For mixing procedures and ratios? Which standard did the authors use?

4.     What is the meaning of “A/F-0/2-T-G-L”?

5.     Please use “×” instead of “x”.

6.     Please give test methods, including the method described by Bhatty in Section 2.2 Test Methods.

7.     Please give only results and discussion in Section 3.

8.     The relevant literature must discuss the results in the paper.

9.     “The authors obtained for a mortar curing at 7 and 28 days a degree of hydration of 60,60 % and 66,96 %”. Please use “.” As a decimal separator.

10.  Fig 7: Are you sure it is Ettrengite? It is like C-S-H. Ettringites are a rod-like crystals.

11.  Fig 8: “Portlandite (C3S)”. What is portlandite? Portlandite, also known as calcium hydroxide, is a chemical compound with the formula Ca(OH)2.

12.  Please rewrite section 3.3 or remove it.

13. Throughout the text, some typos must be eliminated.

14.  I strongly suggest for authors present their conclusions more concisely, avoiding repetition of the obvious and simple results.

 

 

Author Response

The authors would like to thank the contribution of the reviewer for their thorough examination of the manuscript and valuable comments, which will undoubtedly enhance the manuscript’s quality.

The authors’ response to the reviewer’s suggestions and the revised version of the manuscript. are attached.

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Authors,

I had the pleasure to review your manuscript "An approach to understanding the hydration of cement-based composites reinforced with untreated natural fibers."

In my opinion, the manuscript presents interesting data and is well organized in proper sections, getting straight to the point and is easy to understand for all types of readers.

More in detail

In the introduction, the authors have done a good job of outlining the state of the art in researching environmentally friendly materials. In this section, the authors frame the focus of their research well with a considerable amount of bibliography.

In the Materials and Methods section, the characterisation of the raw materials used and the description of how the tests were performed are well explained and described.

In the results section, the authors present the results of their experiments well and clearly describe all the steps of material curing they have investigated. I appreciated the structure of the paragraph, in my opinion well organized and understandably written.

The conclusions of this manuscript are supported by appropriate evidence and provide good answers to the aims of the study. The results and the references well support the conclusion.

For all these reasons, only a few minor changes are requested

Comments for author File: Comments.pdf

Author Response

The authors would like to thank the contribution of the reviewer for their thorough examination of the manuscript and valuable comments, which will undoubtedly enhance the manuscript’s quality.

The authors’ response to the reviewer’s suggestions and the revised version of the manuscript. are attached.

Author Response File: Author Response.pdf

Reviewer 4 Report

This paper presents the TGA-dTGA test carried out on mortar samples with and with out fibers at different age and deals with the hydration degree, hydration products and microstructure of OPC mortar with and without untreated natural hemp fibers to explore the effect of fibers in mortar composite. The morphologies of hydration products at different ages were evaluated using a SEM-EDX analysis.

I believe that the paper is very well structured, that the results are clearly presented, and the methodology is very well applied.

I suggest replacing the yellow color in the pictures (i.e. on the graphs) with another darker color so that the printed version of the work is clearer. Also, for the same reason, in Figure 5 I suggest painting the gray columns with a lighter color.

However, I have some concerns and I kindly ask the authors for the clarification. Please explain in the manuscript why (reason) and how (method) the fibers were cut to a length of 0.5 to 2 mm, why the length of all fibers is not the same, and how the weight fraction of fibers was chosen with respect to the weight of cement (why 1 %). Please explain and provide references that support the claims made. Also, I wonder why was hemp fiber chosen, and not the fiber of, for example, some cereals? In addition, please describe in detail in the manuscript how the mixtures were made. Were the fibers and cement mixed dry and then the water was added to that mixture or the procedure was different? This explanation will ensure reproducibility of tests and results.

Finally, I kindly ask the authors to provide guidelines and suggestions for further research in Conclusion.

Author Response

The authors would like to thank the contribution of the reviewer for their thorough examination of the manuscript and valuable comments, which will undoubtedly enhance the manuscript’s quality.

The authors’ response to the reviewer’s suggestions and the revised version of the manuscript. are attached.

Author Response File: Author Response.pdf

Reviewer 5 Report

 

1. Can the authors elaborate on the specific uncertainties surrounding the influence of untreated natural fibers on the hydration process of Portland cement composites, and how these uncertainties may impact the findings of the study?
2. How do the authors justify the use of differential thermal and thermogravimetric analysis as the most common tests to analyze the degree of hydration of cement composites, and what are some potential limitations of these tests?
3. Can the authors provide more detail on Bhatty's method for calculating the degree of hydration of cement composites, and how it was applied in this study?
4. What are some potential mechanisms by which untreated natural hemp fibers increase the degree of hydration of OPC mortar, and how do these mechanisms relate to the broader literature on fiber-cement composites?
5. Can the authors explain why the degree of hydration decreased between 14 and 28 days in samples with and without fibers, and what implications this finding may have for the practical use of cement composites?
6. How do the authors reconcile the finding that fibers increase the formation of monosulphate but not ettringite, and what are the potential reasons for this discrepancy?
7. How do the authors explain the relationship between the presence of fibers and portlandite content, and how does this relationship inform our understanding of the role of fibers in cement composites?
8. How do the XRD patterns of OPC mortar with and without fibers differ, and what are the implications of these differences for the strength and durability of the composite? Can the authors provide more detail on how the level of calcite is affected by the presence of fibers, and how this may impact the sustainability of cement composites?
9. How do the authors address potential environmental concerns related to the use of untreated natural hemp fibers in cement composites, and what steps can be taken to mitigate these concerns?
10. Can the authors provide additional insights into the variation in hydration process observed between different particles of belite, and how this variation may affect the overall strength and durability of the composite?
11. How do the findings of this study compare to those of previous research examining the effect of natural fibers on cement composites, and what are some potential areas for future research in this field?
12. How does the addition of synthetic fibers compare to natural fibers in terms of their impact on the hydration process and microstructure of cement composites?
13. Can the authors elaborate on the specific effects of fiber length and content on the hydration process of cement composites, and how these factors were accounted for in the study?
14. How can the findings of this study be applied in practical contexts, such as in the development of more sustainable construction materials?
15. Can the authors provide additional insights into how the microstructure of cement composites can be optimized for strength and durability, and what implications this has for the use of natural fibers? And what are some potential drawbacks of adding natural fibers to cement composites, and how can these drawbacks be mitigated in practice?
16. How can future research build on the findings of this study to further our understanding of the effect of natural fibers on cement composites, and How can the insights gained from this study be translated into practical industrial applications, and what are some potential challenges associated with scaling up the use of natural fibers in cement composites?

 

 

Author Response

The authors would like to thank the contribution of the reviewer for their thorough examination of the manuscript and valuable comments, which will undoubtedly enhance the manuscript’s quality.

The authors’ response to the reviewer’s suggestions and the revised version of the manuscript. are attached.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have made the necessary chenges. Therefore The manuscript can be accepted.

Author Response

The authors would like to thank the contribution of the reviewer for his thorough examination of the manuscript and valuable comments, which will undoubtedly enhance the manuscript’s quality.

Reviewer 4 Report

I can confirm that the authors have addressed all the issues in the manuscript and significantly improved its content.

However, I kindly ask the authors to once again read and check the information written in response to my 4th comment, namely:

"To analyze the degree of hydration, different tests were carried out on samples with and without fibers at age of 2, 3, 7, 14 and 28 days. Cubic mortar samples sized 30x30x3 mm were manufactured according to the standard [45]. The procedure for mixing the materials was, with the planetary mixer running, the water and cement Portland was introduced and mixed for 30 seconds. The next step was the introduction of the sand and the fiber and mixed for 30 seconds more. Finally, stopped 30 seconds the mixer, remove the material adhering to the walls and mixed for 60 seconds. All the materials were added dry."

I do not understand the following parts:

"...Cubic mortar samples sized 30x30x3 mm..." Where they really 30x30x3 mm or perhaps 30x30x30 mm? The size of 3 mm seems very small.

"Finally, stopped 30 seconds the mixer..:" This part I do not understand.

I suggest rewriting the whole paragraph by a native English speaker.

Also, I suggest writing s instead of seconds (SI units should be used)

 

Author Response

The authors added the response of each comment in a attached document

Author Response File: Author Response.pdf

Reviewer 5 Report

the revised manuscript can be accepted. 

Author Response

The authors would like to thank the contribution of the reviewer for his thorough examination of the manuscript and valuable comments, which will undoubtedly enhance the manuscript’s quality.