Investigating the Influence of Fiber Content and Geometry on the Flexural Response of Fiber-Reinforced Cementitious Composites

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this manuscript, authors investigates the impact of such tiny diameter carbon and micro polypropylene fibers on the flexural performance of FRCCs. The overall study aims to investigate the impact of different fiber types (carbon, micro, macro polypropylene and sisal fibers) on the compressive and flexural strength, as well as the initial cracking resistance and post-cracking behavior of cementitious composites reinforced with fibers. The topic of the paper is well worth researching. However, Since the corresponding research results in this paper is used for industrial application. there are still a few points required to be explained in more details or added on the innovation and practicability of the article, as follows.

(1) The abstract effectively outlines the study's focus on FRCCs, particularly emphasizing the geometric properties of micro and macro fibers. The authors need to highlight the novelty of the work presented. Please, demonstrate more obvious your innovation in this work. Would you mind identifying discrimination between your work and others?

(2) The findings regarding the brittleness of carbon fiber-reinforced composites (CFRCCs) post-cracking and their improved flexural strength are insightful. However, a more detailed discussion on the underlying mechanisms contributing to these behaviors (e.g., interfacial bonding, fiber-matrix interaction) would enhance the understanding of the results.

(3) The implications of the findings on practical applications of FRCC are significant, particularly concerning the trade-offs between strength, ductility, and toughness based on fiber characteristics. Discussing how these findings could inform material selection or engineering design criteria would enhance the relevance of the study to the field of construction materials.

(4) Discussing the practical implications of the study's findings, such as optimizing fiber content and aspect ratios to enhance structural performance, would add value. Additionally, proposing future research directions, such as exploring novel fiber types or modifying matrix compositions, could further advance the field.

 

(5) The details of the article need to be noted. The samples in the figure need to be specified, for example, each item in Figure 1 needs to be specified, and the specific experimental equipment model needs to be specified in Figure 2

Comments on the Quality of English Language

The manuscript also required a spell/grammar check. For example, there two “fibers” in the same sentence in the conclusion 3. Please improve English and engage native proof-reader if available, and all references should be checked according to the requirements of journal.

Author Response

Comments 1: The abstract effectively outlines the study's focus on FRCCs, particularly emphasizing the geometric properties of micro and macro fibers. The authors need to highlight the novelty of the work presented. Please, demonstrate more obvious your innovation in this work. Would you mind identifying discrimination between your work and others?

Response 1: Agree. In the abstract , the novelty of the work is highlighted in red color and this text added to show the novelty clearly “ There has been no research undertaken in the literature to forecast the ratio of ultimate flexural strength to initial cracking strength of FRCC. In the present work, regression analysis was performed on data from this study and earlier publications to establish an equation that forecasts the modulus of rupture (MOR) to initial fracture strength. This ratio also demonstrates FRCC's flexural behavior, which can be deflection hardening or deflection softening. This highlighted text also discriminate my work with other researcher , where all researchers determined first cracking strength and ultimate flexural strength but there is no relation or correlation between them. In this research this ratio predicted

Comment 2:  The findings regarding the brittleness of carbon fiber-reinforced composites (CFRCCs) post-cracking and their improved flexural strength are insightful. However, a more detailed discussion on the underlying mechanisms contributing to these behaviors (e.g., interfacial bonding, fiber-matrix interaction) would enhance the understanding of the results.

Response 2: Agree/ There is no standard test method to determine the interfacial bond strength between fiber and matrix  particularly for these tiny size fibers like carbon fiber embedded in cement matrix , but the microscopic studies in figure 10 (SEM image of carbon fibers in a mortar matrix. both Interfacial bond and matrix failure occurred at the maximum flexural load). this figure  demonstrate that most of the fibers were pulled out at maximum flexural load and matrix rupture this indicated that the interfacial bond strength between carbon fiber and matrix was high. The carbon fibers within the composite help in distributing and transferring the applied loads across a larger area. This distribution minimizes the stress concentration points within the matrix and allows the composite to bear greater loads before reaching failure. The smooth surface texture of carbon fibers can lead to weak bonding with the cementitious matrix. While the fibers contribute to the initial load-bearing capacity, the poor interfacial bond can limit their ability to effectively bridge cracks and transfer stress once the matrix begins to crack. These were added in the text at page 16 & 17 highlighted in red color.

Comment 3: The implications of the findings on practical applications of FRCC are significant, particularly concerning the trade-offs between strength, ductility, and toughness based on fiber characteristics. Discussing how these findings could inform material selection or engineering design criteria would enhance the relevance of the study to the field of construction materials.

Response 3 : Agree/The experimental work and regression analysis conducted on the available data, including references, revealed that the volume fraction, aspect ratio, and tensile strength of fibers, along with the compressive strength of the matrix, can be utilized to predict the ratio of ultimate flexural strength (Modulus of rupture) to first cracking strength of FRCCs. This ratio provides an approximation for the behavior of Fiber Reinforced Cementitious Composites (FRCCs), which can either exhibit deflection hardening behavior or deflection softening behavior. Moreover, the flexural strength test, also known as the cracking strength, of control specimens without fibers can be measured in a laboratory using any open loop system equipment. This value can then be used to estimate the ultimate flexural strength by selecting appropriate fiber type and parameters. Subsequently, the tensile strength of fiber reinforced cementitious composites (FRCCs) can be predicted, which can be utilized for constructing structural members reinforced with fibers.

Comment 4: Discussing the practical implications of the study's findings, such as optimizing fiber content and aspect ratios to enhance structural performance, would add value. Additionally, proposing future research directions, such as exploring novel fiber types or modifying matrix compositions, could further advance the field.

Response 4: Agree/ This study differs from the conventional approach of analyzing the bond strength between the fiber and matrix interface. Instead, it introduces two interconnected qualities that are strongly associated with bond strength: fiber tensile strength and matrix compressive strength. Further investigation is advised to determine the actual interfacial bond strength between the fiber and matrix for various fiber types. Subsequently, the prediction of interfacial bond strength can be determined by considering multiple parameters related to the fibers and matrix. This enhancement will directly contribute to the accurate prediction of bond strength which is used to predict the tensile strength and flexural strength of fiber-reinforced cementitious composites (FRCCs). Additionally, it is crucial to conduct a reliability study to validate these predicted equations. This can be achieved by applying the equations to real structural members reinforced with fibers and rebars, utilizing the beam theory and stress distribution equations. This paragraph is included as a recommendation for future development.

Comment 5: The details of the article need to be noted. The samples in the figure need to be specified, for example, each item in Figure 1 needs to be specified, and the specific experimental equipment model needs to be specified in Figure 2

Response 5: Agree/ These specifications added to figure 1 and figure 2

 

 

Reviewer 2 Report

Comments and Suggestions for Authors

The paper needs to be revised in English and clarified in specific sentences. It would benefit to be in a more concise and clear writting.

Please see some suggestions in annex.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The paper needs to be revised in English and clarified in specific sentences. It would benefit to be in a more concise and clear writting.

Please see some suggestions in annex.

Author Response

Comments and suggestion for author : The paper needs to be revised in English and clarified in specific sentences. It would benefit to be in a more concise and clear writing.

Response: Agree / I have submitted the article to MDPI Author services for English Editing and it has undergone revision. The unique identifier for Author Services is english-83918. I have addressed all of the points that are made in the text.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors The author 's comments are a good answer to the comments. I recommend publishing after checking for minor grammatical errors and checking references according to the requirements of the journal. Comments on the Quality of English Language There are some small errors, it is recommended to carefully check before publication.

Author Response

Comments and Suggestions for Authors: The author's comments are a good answer to the comments. I recommend publishing after checking for minor grammatical errors and checking references according to the requirements of the journal.

Response : Thank you for your comment. I have reviewed all the sections marked in yellow and made the necessary corrections. Additionally, I have also verified all the references and modified them as per the journal's requirements. The sections now highlighted in blue have been addressed as well.

Comments on the Quality of English Language: There are some small errors, it is recommended to carefully check before publication.  Response: I thoroughly reviewed the entire paper and diligently implemented the corrections made by the language editor service. As a result, I was able fix a number of errors.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors improved significantly the paper, which may be published after the following editing suggestions:

1 - Page 3, linne 113

Where is "soft fibers, that which have"vwrite "soft fibers that which have"

2 - Page 4, lines 146/147

Where is "and various lengths was prepared by cutting the cord 146 to the following lengths: 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, hence 30 mm. and thus" write "and various lengths were prepared by cutting the cord 146 to the following lengths: 5 mm, 10 mm, 15 mm, 20 mm, 25 mm and 30 mm. Hence,..."

Line 152

Where is "Two types of polypropylene fiber was used in this study" write "Two types of polypropylene fiber were used in this study"

3 - Page 6, line 189

Where is "The G1 fibers had a constant length of 5 mm, whereas the G3 fibers" write "The G1 fibers had a constant length of 5 mm, whilst the G3 fibers"

Comments on the Quality of English Language

The authors improved significantly the paper, which may be published after the following editing suggestions:

1 - Page 3, linne 113

Where is "soft fibers, that which have"vwrite "soft fibers that which have"

2 - Page 4, lines 146/147

Where is "and various lengths was prepared by cutting the cord 146 to the following lengths: 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, hence 30 mm. and thus" write "and various lengths were prepared by cutting the cord 146 to the following lengths: 5 mm, 10 mm, 15 mm, 20 mm, 25 mm and 30 mm. Hence,..."

Line 152

Where is "Two types of polypropylene fiber was used in this study" write "Two types of polypropylene fiber were used in this study"

3 - Page 6, line 189

Where is "The G1 fibers had a constant length of 5 mm, whereas the G3 fibers" write "The G1 fibers had a constant length of 5 mm, whilst the G3 fibers"

Author Response

Comments and Suggestions for Authors: The author's comments are a good answer to the comments. I recommend publishing after checking for minor grammatical errors and checking references according to the requirements of the journal.

Response : Thank you for your comment. I have reviewed all the sections marked in yellow and made the necessary corrections. Additionally, I have also verified all the references and modified them as per the journal's requirements. The sections now highlighted in blue have been addressed as well.

Comments on the Quality of English Language: There are some small errors, it is recommended to carefully check before publication. 

Response: I thoroughly reviewed the entire paper and diligently implemented the corrections made by the language editor service. As a result, I was able fix a number of errors.

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

Comments and Suggestions for Authors

The author's reply is very good, I recommend accepting it

Author Response

Comments and Suggestions for Authors: The author's reply is very good; I recommend accepting it

Response: I am grateful for your insightful comments and valuable assessment of my article.

Reviewer 2 Report

Comments and Suggestions for Authors

The paper stil needs minor editing as follows.

1 -Line 115 - where is "...soft fibers, that which have lower elastic moduli than rigid steel fibers." write "... soft fibers that have lower elastic moduli than rigid steel fibers.

 

2 - Lines 149/150 - where is " various lengths was prepared by cutting the cord 149 to the following lengths: 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, hence 30 mm. and thus..." write " various lengths were prepared by cutting the cord 149 to the following lengths: 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, and 30 mm. Hence,..."

3 - Lne 155 - where is "Two types of polypropylene fiber was used in this study" write "Two types of polypropylene fiber were used in this study"

Comments on the Quality of English Language

The paper stil needs minor editing as follows.

1 -Line 115 - where is "...soft fibers, that which have lower elastic moduli than rigid steel fibers." write "... soft fibers that have lower elastic moduli than rigid steel fibers.

 

2 - Lines 149/150 - where is " various lengths was prepared by cutting the cord 149 to the following lengths: 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, hence 30 mm. and thus..." write " various lengths were prepared by cutting the cord 149 to the following lengths: 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, and 30 mm. Hence,..."

3 - Lne 155 - where is "Two types of polypropylene fiber was used in this study" write "Two types of polypropylene fiber were used in this study"

Author Response

Comments and Suggestions for Authors

The paper still needs minor editing, as follows: Line 115, Line 149/150 and Line 155

Response : Agree : These lines 115, 149/150, and 155 are corrected and highlighted with green color

Thanks for the comments

 

Author Response File: Author Response.pdf

Round 4

Reviewer 2 Report

Comments and Suggestions for Authors

The paper can be published