Study on the Influence of Sugarcane Bagasse Fiber on the Physical and Mechanical Properties of Lightweight Mortar

Comments 1: [Data Discrepancy in Mixture Design: In Table 6, the values ​​in the "Fiber (%)" column are listed as 4, 8, 12, and 16. However, the text clearly states that the fiber ratios are 0.4%, 0.8%, 1.2%, and 1.6%. This is a very serious typographical error that misrepresents the entire experimental design and should be corrected immediately to avoid misleading the reader.]

Response 1: Thank you for pointing out this important typographical error. We have carefully checked and corrected the values in the “Fiber (%)” column of Table 6 from 4, 8, 12, and 16 to 0.4, 0.8, 1.2, and 1.6, respectively, to ensure consistency with the experimental design described in the text and to avoid misleading readers. (Page 5, Lines 152)

Comments 2: [Clarification of Water/Binder Ratio: Table 6 shows that 400 g of water was used for every 350 g of cement. This indicates a fairly high water/cement ratio of approximately 1.14. Although lightweight aggregates and natural fibers have a high water absorption capacity, the authors should clearly discuss the "effective water/binder ratio" in the methodology section and justify this mix design on a scientific basis.]

Response 2: Thank you for this valuable comment. We acknowledge this important point. The water amount reported in Table 6 corresponds to the total mixing water. Because vitrified microbeads and sugarcane bagasse fibers are highly absorbent, part of the added water is absorbed during mixing and early curing, and thus the effective water-to-binder ratio is expected to be lower than the nominal value calculated from total water. We have revised the Methodology section to clarify this and to justify the relatively high total water dosage adopted to ensure adequate workability and proper casting/compaction. Due to experimental constraints, the effective water-to-binder ratio was not directly quantified in the present work; future studies will further measure it.  (Page 5, Lines 133–151)

Comments 3: [Terminology: The term "dosage" (e.g., "dosages of 0%, 0.4%...") has been used very frequently for fibers. Although dosage is used for additives in materials science, using "fiber content" or "fiber volume fraction" for aggregates and fibers is more accurate and professional.]

Response 3: Thank you for this helpful suggestion. We agree that “fiber content” is more accurate and professional than “dosage” when referring to fibers in the present study. Accordingly, we have revised the manuscript throughout and replaced the term “dosage” with “fiber content” where appropriate to improve the precision and consistency of the terminology.

Comments 4: [Figure Axes and Labels:

1.The y-axis of Figure 4 is labeled "Liquidity/mm". To be consistent with the text, this should be changed to "Consistency" or "Flow spread".

2.The y-axis of Figure 8 is labeled "Break off strength/MPa". This naming convention is not standard in the literature; it should be corrected to "Flexural strength/MPa" to match the section title and terminology.

3.The SEM images in Figure 14 are incorrectly labeled as (a), (b), (b), (d), (e), (f). The second "(b)" label should be corrected to "(c)".]

Response 4: Thank you for these careful and helpful comments. We have revised the figure labels accordingly. Specifically, the y-axis label in Figure 4 has been corrected from “Liquidity/mm” to “Consistency” to ensure consistency with the terminology used in the main text. The y-axis label in Figure 8 has been revised from “Break off strength/MPa” to “Flexural strength/MPa” to conform to standard terminology and match the section title. In addition, the duplicated panel label in Figure 14 has been corrected, and the second “(b)” has been changed to “(c)”. These revisions have been made in the manuscript to improve accuracy and avoid confusion.

Comments 5:[Writing Style: Avoid starting consecutive sentences or paragraphs with "As shown in Figure X". Stating the scientific finding first and adding the figure reference in parentheses at the end of the sentence will improve the flow of the text.]

Response 5:Thank you for this helpful suggestion. We have carefully revised the relevant text throughout the manuscript to avoid repeatedly beginning consecutive sentences or paragraphs with “As shown in Figure X”. The scientific findings are now presented first, followed by the corresponding figure citations in parentheses, in order to improve the flow, readability, and overall academic style of the manuscript.

Comments 6:[Expanding Conclusions: The current conclusions section consists only of a summary and a bulleted repetition of the findings. Authors should add comprehensive statements on the limitations of the current study, suggestions for future studies, and how the obtained optimum fiber content practically contributes to the "double-carbon" targets mentioned in the introduction.]

Response 6:Thank you for this valuable suggestion. We agree that the original Conclusions section mainly summarized the main findings and did not sufficiently address the limitations of the present study, future research directions, or the practical relevance of the optimum fiber content to the “dual-carbon” targets mentioned in the Introduction. Accordingly, we have revised and expanded the Conclusions section. Specifically, we added statements on the limitations of this study, including the laboratory-scale nature of the experiments and the lack of direct quantification of the effective water-to-binder ratio and life-cycle carbon-reduction benefits. We also included suggestions for future work, such as fiber pretreatment, length effect, dispersion control, durability testing, life-cycle assessment, and engineering-scale validation. In addition, we further clarified that the appropriate incorporation of sugarcane bagasse fiber can promote the valorization of agricultural waste and provide a useful reference for the development of green lightweight building materials under the “dual-carbon” strategy. (Page 2, Lines 79–89)(Page 17, Lines 539–549)

Comments 7:[Reference Formatting: The reference list should be checked for consistency according to the journal guidelines. While some references use the format "[J]" to indicate that it is a journal article or "[C]//" for a conference paper, others lack these markings. The entire bibliography should be standardized to conform to the journal's uniform referencing style.]

Response 7:Thank you for this careful comment. We have thoroughly checked and revised the entire reference list to ensure consistency with the journal’s formatting requirements. Specifically, the bibliography has been standardized according to the journal’s uniform referencing style, and inconsistencies in the use of reference-type markings have been corrected throughout the manuscript.

Comments 1: [The authors state that at low fiber doses, compactness increases, porosity decreases, and water absorption increases. It is not normal for water absorption to increase while compactness increases. The authors should explain this situation in their study.]

Response 1: Thank you for this valuable comment. We have added a brief clarification in the revised manuscript. The discussion now notes that the increase in water absorption at low fiber contents may be associated with the presence and water affinity of the fibers, while the further increase at high fiber contents may be related to fiber agglomeration and increased pore connectivity. As this mechanism was not directly quantified in the present study, the explanation has been kept cautious and concise. (Page 9*, Lines 304–312) (Page 10*, Lines 330–341)

Comments 2: [The innovative contribution of the study should be clarified.Is the innovation the combination of NMR and fractal analysis?]

Response 2: Thank you for this valuable comment. We agree that the innovative contribution of this study should be clarified. The contribution of the present work does not lie solely in the combination of LF-NMR and fractal analysis. Rather, it lies in systematically investigating the effects of sugarcane bagasse fiber on the physical properties, mechanical performance, pore structure, and interfacial transition zone characteristics of lightweight mortar, while using LF-NMR, fractal analysis, and SEM as complementary tools to support the interpretation of the microstructure–property relationship. We have revised the manuscript accordingly to clarify this point.

Comments 3: [NMR Assumptions, ρ = 5 nm/ms, pore geometry cylindrical, Fs = 2. It is necessary to explain whether these values were taken from the literature or how they were obtained.]

Response 3: Thank you for this comment. The assumptions of cylindrical pore geometry (Fs = 2) and ρ₂ = 5 nm/ms were adopted from previous NMR studies on cement-based materials, rather than determined experimentally in the present work. We have revised the manuscript to clarify that these values are literature-based assumptions used for pore-size conversion. (Page 7, Lines 240–247)

Comments 4: [Table 6 lists the fiber ratio as “4, 8, 12, 16,” but the text specifies it as 0.4%, 0.8%, 1.2%, and 1.6%.]

Response 4: Thank you for pointing out this typographical error. We have corrected the fiber ratios in Table 6 from “4, 8, 12, and 16” to “0.4%, 0.8%, 1.2%, and 1.6%” to ensure consistency with the text and avoid misleading readers. (Page 5, Lines 152)

Comments 5:[The study indicates that a higher D value corresponds to better mechanical performance. However, the fractal dimension indicates the complexity of the pore distribution. It is not always linearly positively correlated with strength.

I recommend providing regression analysis between D and compressive strength and adding the correlation coefficient.]

Response 5:Thank you for this valuable comment. We agree that the relationship between fractal dimension and mechanical performance should not be described as a simple linear positive correlation without further verification. In response to this suggestion, we have added a regression analysis between the fractal dimension and compressive strength in the revised manuscript, together with the corresponding correlation coefficient. The relevant discussion has also been revised to present this relationship in a more rigorous and quantitative manner. (Page 14, Lines 452-470)

Comments 6:[The ITZ thickness was not measured in the SEM section. This thickness information can be provided using the measurement bar on the SEM image.]

Response 6:Thank you for this valuable comment. We agree that the SEM analysis in the present study is primarily qualitative, and no direct measurement of ITZ thickness was performed. In the revised manuscript, we have carefully revised the relevant SEM descriptions to avoid overly quantitative or deterministic statements and to ensure that the discussion remains consistent with the qualitative nature of the SEM observations. The revised text now emphasizes observed interfacial features, such as pores, microcracks, fiber bridging, and hydration-product adhesion, without implying direct thickness measurement.(Page 16, Lines 478–503)

Comments 7:[short questions: How exactly was the fiber volume ratio calculated?

Was the w/b ratio kept constant?

How was the distribution of fibers controlled?]

Response 7:Thank you for these helpful questions. We have clarified the relevant methodological details in the revised manuscript. Specifically, the fiber content is now explicitly defined as the fiber volume fraction relative to the total volume of the mortar mixture. We have also clarified that the total mixing water was kept constant for all mixtures; therefore, the nominal water-to-binder ratio based on the total added water remained unchanged, whereas the effective water-to-binder ratio may vary because of water absorption by the lightweight aggregate and sugarcane bagasse fiber. In addition, a brief description of the mixing procedure has been added to explain how fiber distribution was controlled, namely by gradually introducing the fibers in small increments and applying sufficient mixing, including an additional short period of high-speed mixing for the fiber-reinforced mixtures, to improve homogeneity and reduce visible agglomeration.

Comments 8:[according to authors: “…. at higher dosages, the fibers are more likely to form agglomerates, leading to the restoration and increase of mortar flowability”

This is technically incorrect. Fiber agglomeration generally reduces flow.

High fiber content, clumping, heterogeneous water distribution, and segregation may have caused an anomaly in the measured flow value.]

Response 8:Thank you for this important comment. We agree that the previous wording was not sufficiently accurate. The slight increase in the measured consistency at higher fiber contents should not be interpreted as a genuine improvement in flowability caused by fiber agglomeration. In the revised manuscript, we have therefore revised this description and clarified that the limited variation in the measured flow value may be associated with high fiber content, local fiber clumping, heterogeneous water distribution, and possible segregation during mixing. The relevant discussion has been made more cautious and concise. (Page 9*, Lines 304–312) (Page 10*, Lines 330–341)

Comments 1: [The description of the raw materials and the rationale for their use should be improved.

Table 1: please write pH instead of PH.

What is meant by Chemical content?

What type of cement was used (CEM I, CEM II, etc.)?

What was the chemical and mineralogical composition of the sand used? Was it of siliceous or silico-calcareous origin?

What is meant by Surface porosity in Table 4?

What was the purpose of using a cellulose ether? What type of etherification did the polymer present?

What is the composition of the redispersible polymer powder? For what purpose was it used?]

Response 1: Thank you for these helpful comments. We have revised the raw-material description to improve clarity and accuracy. Specifically, “PH” has been corrected to “pH”, and the unclear term “Chemical content” has been replaced with the specific water-quality index “chloride”. We have also clarified that the cement used in this study was ordinary Portland cement (P·O 42.5) conforming to Chinese standard GB 175. In addition, the term “Surface porosity” in Table 4 has been revised to “closed-pore ratio” to better reflect its actual meaning.Since the present study did not include separate chemical characterization of these admixtures, their detailed composition was not determined herein, and the related description was provided based on the supplier’s product information. (Page 2, Lines 92–107) (Page 5, Lines 133–151)

Comments 2: [Some experimental procedures also need to be completed.

For instance, the experimental procedures for LF-NMR and SEM measurements are clearly incomplete, which prevents the reproducibility of the research. Essential information should be provided, such as the equipment used, measurement conditions, and sample preparation procedures (e.g., metallization or coating), among others.]

Response 2: Thank you for this valuable comment. We have revised the experimental procedures for LF-NMR and SEM in the manuscript by adding the relevant equipment information, measurement conditions, and sample preparation details, so as to improve the clarity and reproducibility of the study. (Page 7, Lines 215–224)

Comments 3: [Some discussions need to be improved, expanded, and clarified.

Section 3.1: How can it be assumed that an increase in fiber content results in greater fluidity of the fresh mortar? The formation of fiber agglomerates would be expected to hinder the flow of the liquid phase, thereby increasing viscosity. Furthermore, Section 3.2 indicates that the reduction in compaction observed at high fiber dosages would increase water absorption. This would likely reduce the flow spread, which contradicts the results presented in Section 3.1. The authors should examine this issue in greater depth and provide a clearer explanation.

The SEM analysis, although presenting high-quality images, is incomplete. The fiber proportions corresponding to the images are not indicated. Moreover, there is no comparative study between the different fiber contents that would allow the previously reported results to be visually and clearly corroborated. This section should be substantially improved.]

Response 3: 

Thank you for these valuable comments. We agree that the discussion in Section 3.1 required further clarification. In the revised manuscript, we have revised the relevant text to avoid interpreting the slight increase in the measured consistency at high fiber contents as a genuine improvement in flowability. The discussion is now more cautious and clarifies that this limited variation may be associated with local fiber clumping, heterogeneous water distribution, and possible segregation during mixing, rather than enhanced fluidity. We have also adjusted the wording in the density and water-absorption discussions to maintain consistency among the different sections.

Regarding the SEM analysis, we agree that the original presentation was incomplete. In the revised manuscript, the corresponding fiber contents of the SEM images have been clearly indicated, and the discussion has been reorganized according to the different mixtures. Specifically, the control group and the fiber-containing mixtures with relatively low and high fiber contents are now discussed separately, so that the microstructural observations can better support the previously reported pore-structure and mechanical results. At the same time, we have kept the SEM interpretation qualitative and cautious, limiting the discussion to the features that can be directly observed in the images. (Page 9*, Lines 304–312) (Page 10*, Lines 330–341)

Comments 4: [The manuscript should improve the reporting of variability and statistical significance. Sections 3.4, 3.5, and 3.6: the results presented in Figures 7, 8, and 9 should include error bars in order to assess the variability and statistical significance of the measurements.]

Response 4: Thank you for this valuable comment. We agree that reporting variability and statistical significance would improve the rigor of the mechanical-property results. In the revised manuscript, we have clarified in the Methods section that three parallel specimens were tested for each mixture and that the reported values represent the mean results. However, due to the limited number of specimens and the unavailability of some original early-age data for repeat statistical processing, complete error bars and significance analysis could not be added for all data points in the present revision. We have therefore kept the discussion appropriately cautious and avoided overstating small differences among mixtures. (Page 6, Lines 192–207)

Comments 5:[Some sections should be reorganized.

Section 3.7.1: The mathematical methods and models associated with this technique should be moved to the Materials and Methods

Section 3.7.2: The methods used to calculate the fractal dimension should also be included in the Materials and Methods]

Response 5:Thank you for this valuable suggestion. We agree that the mathematical models and calculation procedures related to LF-NMR and fractal analysis are more appropriately presented in the Materials and Methods section rather than in the Results and Discussion section. Accordingly, in the revised manuscript, the relevant theoretical equations and calculation methods originally presented in Sections 3.7.1 and 3.7.2 have been reorganized and moved to the Materials and Methods section. As a result, Sections 3.7.1 and 3.7.2 now focus primarily on the experimental results and their interpretation.

Comments 6:[Figure 12: It is understood that the inequality represented by the red signal in the legend corresponds to >1000 nm, rather than what is currently indicated.]

Response 6:Thank you for this careful comment. We agree that the legend in Figure 12 was inaccurate. In the revised manuscript, the corresponding red range has been corrected to >1000 nm to ensure consistency with the pore-size classification and to avoid misunderstanding.(Page 13, Lines 442)