Structural Evaluation with FWD of Asphalt Pavement with 30% RAP Reinforced with Fiberglass Geogrid in the Asphalt Layer

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The subject of this paper, entitled “Structural evaluation by deflection of the RAP pavement reinforced with fibreglass geogrid” is related to verifying the use of recycled asphalt pavements (RAP), considering a falling weight deflectometer (FWD) device. Both contain 30% RAP, and one of them has fibreglass geogrid in the center of the asphalt layer.

So, the objective of the paper is relevant.

The title and abstract reflect the content of the paper. The methodology is adequate, but some tests used for the material are outdated.

In Scheme 1, the terminology of the layers of the road pavement is not the one currently adopted. Please correct them.

In the same Scheme 1, Z1 and Z2 should represent two variants of the RAP-Geogrid system. In the figure, it seems that Z1 and Z2 correspond to two different loads. Please modify the drawing.

It would be useful to add the granulometric characteristics of the mixtures (grade curve).

It is not specified whether a regenerating or fluxing additive was used in the mixture.

This means that the use of the centrifuge machine to separate asphalt from the stone aggregate is able to eliminate the aged bitumen from the RAP.

It would be useful to have control over the quantity of aged bitumen contained in the mixture.

It would be appropriate for the authors to highlight that the characterization tests used for the mixtures (Marshall) and for the sub-bases (CBR) are now outdated. However, it would be appropriate to cite the relevant international legislation in the bibliography.

Author Response

The topic of this article, entitled "Structural Deflection Assessment of RAP Pavement Reinforcement with Fiberglass Geogrid," concerns the verification of the use of recycled asphalt pavements (RAP), considering a dropped weight deflectometer (FWD) device. Both contain 30% RAP, and one of them has fiberglass in the center of the asphalt layer. 

Therefore, the objective of the article is relevant. 

The title and abstract reflect the content of the work. The methodology is adequate, although some tests used for the material are outdated.

A:The tests applied to the material were carried out in accordance with updated manuals, such as N∙CMT∙4∙04/17 of the Ministry of Infrastructure, Communications and Transportation, “Stony Materials for Asphalt Mixtures” from 2017 between lines 143 to 144; N∙CMT∙4∙05-00/22 Ministry of Infrastructure, Communications and Transportation, “Quality of Asphalt Materials” from 2022 between lines 147 - 148 and N∙CMT∙4∙05∙004/18 of the Ministry of Infrastructure, Communications and Transportation, “Quality of Asphalt Cements according to their Performance Grade (PG)” from 2018 cited [38]  in line 202.

In Diagram 1, the terminology for pavement layers is not the one currently adopted. Please correct it. 

A: The terminology for pavement layers has changed. Note between lines 133 and 134.

In diagram 1, Z1 and Z2 should represent two variants of the RAP-Geogrid system. In the figure, it appears that Z1 and Z2 correspond to two different loads. Please modify the drawing. 

A: Diagram 1 has been adjusted to prevent the loads from appearing different. Z1 and Z2 refer to the footprint names of the models presented between lines 133 and 134.

It would be useful to add the granulometric characteristics of the mixture (granulometric curve).

A: The granulometric curve graph was added as figure 2 between lines 160 to 161. 

It is not specified whether a regenerating or fluxing additive was used in the mix. 

A: No additives were used in the mix. This is expressed in line 148.

This means that using the centrifuge machine to separate the asphalt from the stone aggregate can remove aged bitumen from the RAP. 

A: The RAP was incorporated into the mix by dry mixing, as stated on line 195, considering a low or zero amount of aged asphalt in the mix.

 

 

 

 

It would be useful to have control over the amount of aged bitumen contained in the mix. 

A: There is data on the aged asphalt content. This is written on line 151.

The authors would be wise to emphasize that the characterization tests used for the mixture (Marshall) and the subbases (CBR) are now outdated. However, it would be appropriate to cite the relevant international legislation in the bibliography.

A: The bibliography has been updated to indicate that the updated manual M·MMP·4·05·034/23 of the Mexican Ministry of Infrastructure, Communications, and Transportation (Secretaría de Infraestructura, Comunicaciones y Transporte) "Marshall Method" was applied for the mixture characterization for 2023 Note the citation between lines 190 and 191. This manual reference current international legislation D6927-15 Standard Test Method for Marshall Stability and Flow of Asphalt Mixtures in line 226. And ASTM D1883-21 for California Bearing Ratio (CBR) of Laboratory – Compacted Solis in line 131.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

General Assessment
This paper investigates the structural performance of recycled asphalt pavement (RAP) with fiberglass geogrid reinforcement through deflection testing. The study compares two pavement models: one with 30% RAP and fiberglass geogrid reinforcement (Z1) versus one with 30% RAP but no reinforcement (Z2). While the research topic is relevant to sustainable pavement infrastructure, the manuscript suffers from several significant issues that require substantial revision before publication consideration. Key concerns include methodological limitations, inconsistent data presentation, inadequate statistical analysis, and clarity issues in the presentation of results.

Major Review Comments
1. Experimental Design Limitations: The study utilizes only two test sections (Z1 and Z2) with three control points each, which provides an extremely limited dataset for drawing meaningful conclusions. The small sample size undermines the statistical significance of the findings and limits generalizability.
2. Unclear Methodology: Section 2 (Materials and Methods) lacks sufficient detail about the experimental procedures, particularly regarding the testing protocols and data collection methods. The relationship between the falling weight deflectometer tests and the structural evaluation parameters is inadequately explained.
3. Data Analysis Deficiencies: The paper lacks rigorous statistical analysis of the results. There is no assessment of data variability, confidence intervals, or statistical significance of the observed differences between Z1 and Z2.
4. Results Presentation: Figures 7-10 present data in ways that make comparison difficult. The organization of data points and the chosen visualization methods do not effectively communicate the key findings.
5. Structural Framework: The paper lacks a clear theoretical framework connecting the physical properties of the materials (RAP and geogrid) to the expected performance outcomes. This makes it difficult to interpret the results within a broader context.

Specific Review Comments
1. Title: Line 1-3 - The title is appropriate but could be more specific regarding the type of deflection testing performed (FWD).
2. Abstract: Lines 17-37 - The abstract lacks quantitative information about the experimental design (e.g., sample sizes, specific test conditions) and would benefit from more precise reporting of key numerical findings.
3. Introduction: Lines 39-42 - The opening paragraph makes claims about RAP enhancing sustainability without sufficient citation or explanation of the mechanisms by which this occurs.
4. Introduction: Lines 94-96 - The problem statement is delayed until the end of the introduction, weakening the paper's focus from the beginning.
5. Materials: Lines 129-134 - The description of conventional coarse aggregate lacks context for how these properties compare to standard specifications or requirements.
6. Materials: Lines 149-153 - The specifications for the fiberglass geogrid are incomplete. Critical properties such as aperture size, junction efficiency, and tensile modulus are not provided.
7. Figure 2: Line 156 - The image of the fiberglass geogrid lacks scale and detail necessary to understand its structure and integration with the asphalt.
8. Methods: Lines 182-191 - The Marshall method description lacks details about compaction effort, specimen preparation, and testing temperature, which are critical variables.
9. Table 1: Line 189 - The table presents data without error margins or statistical measures, making it impossible to assess data reliability.
10. Figure 4: Line 196 - The stability graph shows inconsistent trends with RAP content that are not adequately explained in the text.
11. Figure 5: Line 203 - The flow results show concerning trends at higher RAP contents that exceed specification limits, but implications are not discussed.
12. Scheme 3: Line 223 - The elastic rebound deflection basin diagram lacks proper axis labels and units, reducing its interpretability.
13. Results: Lines 229-233 - The results section begins with vague statements rather than presenting specific findings. Clear topic sentences would improve readability.
14. Equation 1: Line 292 - The equation for normalized area lacks proper explanation of variables and units, and its theoretical significance is not adequately discussed.
15. Figure 8: Line 300 - The figure plotting normalized area vs. maximum deflection lacks clear delineation between data points from Z1 and Z2, making visual comparison difficult.
16. Structural Index: Lines 306-313 - The explanation of structural index is inconsistent with the mathematical formulation provided in Equation 2, creating confusion.
17. Figure 9: Line 328 - The structural index figure uses color coding without clear explanation in the caption, making interpretation difficult.
18. Dynamic Stiffness Modulus: Lines 338-346 - The description lacks adequate theoretical context for why DSM is an important parameter in pavement evaluation.
19. Figure 10: Line 349 - The dynamic stiffness modulus graph lacks error bars and statistical analysis, making it difficult to assess the significance of differences.
20. Discussion: Lines 357-396 - The discussion largely restates results without providing deeper insights or connecting findings to the broader literature on RAP and geogrid reinforcement.
21. Discussion: Lines 385-396 - The paragraph on dynamic stiffness modulus fails to relate findings to practical implications for pavement design or maintenance.
22. Conclusions: Lines 397-407 - The conclusions make claims about "improvements" without quantifying the magnitude or statistical significance of these improvements.
23. Limitations: Lines 408-421 - Critical limitations regarding the small sample size and limited testing conditions are not addressed in the paper.
24. Conclusions: Lines 422-434 - The final paragraph makes strong claims about methodology effectiveness without acknowledging the preliminary nature of the findings given the limited dataset.
25. References: Several recent and relevant studies on geogrid reinforcement in asphalt pavements are missing from the literature review.
26. Scheme 1: Lines 113-127 - The model footprint diagrams lack detailed dimensions and material specifications needed for replication.
27. RAP Material: Lines 138-145 - The description of RAP material extraction and processing lacks details on aging conditions and extraction efficiency.
28. Methods: Lines 204-208 - The deflection testing procedure description lacks information on temperature control and preconditioning of the test section.
29. Temperature Correction: Lines 255-264 - The description of temperature correction methodology lacks justification for the selected normalization temperature (20°C).
30. Future Research: Lines 435-436 - The paper ends with a vague call for future research without specifying critical knowledge gaps that should be addressed.

Comments on the Quality of English Language

The manuscript exhibits significant linguistic deficiencies that impede clear communication of the research findings. Throughout the text, there is inconsistent usage of technical terminology, creating confusion for readers attempting to follow the experimental procedures and results. The paper suffers from structural issues at the sentence level, with frequent occurrences of run-on sentences, particularly in the introduction and methodology sections, alongside problematic subject-verb agreement in complex constructions.
Verb tense consistency is a persistent issue, with inappropriate shifts between present and past tense within sections describing similar activities. The overreliance on passive voice constructions diminishes clarity and directness, often obscuring the agents responsible for specific research actions. Paragraph organization is frequently problematic, with multiple ideas presented without clear topic sentences or logical transitions between concepts.
Technical writing conventions are inconsistently applied, evident in the variable presentation of numerical data, inconsistent hyphenation of compound terms, and irregular formatting of equations and their associated variables. Figure captions lack the necessary detail for independent interpretation, requiring readers to search the main text for explanatory information.
The manuscript also demonstrates imprecise language use, employing qualitative descriptors where quantitative measurements would be more appropriate, and overusing cautious hedging language that weakens the presentation of findings. Citation and reference formatting inconsistencies further detract from the paper's professional presentation.
These linguistic issues collectively diminish the scientific impact of the research by creating unnecessary barriers to comprehension. A thorough language revision focusing on technical precision, sentence structure, and adherence to scientific writing conventions would significantly improve the manuscript's clarity and accessibility to the intended audience.

Author Response

Reviewer 2

 

1. Limitations of the Experimental Design: The study uses only two test sections (Z1 and Z2) with three control points each, providing an extremely limited data set from which to draw meaningful conclusions. The small sample size undermines the statistical significance of the findings and limits their generalizability.

A: The experimental area was designated at the vehicle access to the graduate parking lot of the Faculty of Construction and Habitat Engineering at the University of Veracruz. This ensures a continuous flow of traffic on the model. Therefore, based on the various distances between vehicle axles, a pair of tracks were drawn that span the access lane, allowing for unloading of one vehicle axle symmetrically distributed across the tires. The model is for a small section of a full-scale experimental model.

2. Unclear methodology: Section 2 (Materials and Methods) lacks sufficient detail on the experimental procedures, particularly regarding test protocols and data collection methods. The relationship between drop-weight deflectometer testing and structural evaluation parameters is not adequately explained.

A: The procedures are detailed in the body of this document based on the experimental process of this work, which focuses on the structural performance of the RAP-Geogrid system mentioned in line 109 as elements that physically interact under loads. The mix design with 30% replacement content is based on the Marshall methodology under the flow parameter according to ASTM D6927-15 in line 226. The geogrid is a product of the company Ecomex, which responded to the request to donate the by-product (not for sale) that we applied in one of the footprint models. The FWD test aims to explore, through the structural index and the dynamic rigidity modulus, the structural behavior of the rolling layers that present the reinforcement versus the layer that does not incorporate it. The objective is to generate a judgment on the physical interaction of the components under traffic loads.

3. Data Analysis Deficiencies: The article lacks a rigorous statistical analysis of the results. Data variability, confidence intervals, and the statistical significance of the observed differences between Z1 and Z2 are not assessed.

A: For the structural index results between Z1 and Z2, there are no statistically significant differences among the control points analyzed under 4 loading levels. The value of F (0.7912) is much lower than the critical value for F (2.7729) and the associated probability (0.5697) is much higher than the typical significance level of 0.05. Therefore, the variations between control points for Z1 and Z2 are not significantly greater than the variations within control points. Observe between lines 395 – 396.

 

4. Presentation of Results: Figures 7-10 present the data in a manner that makes comparison difficult. The organization of the data points and the chosen visualization methods do not effectively communicate the key findings.

A: Now the figures 09 -12 (before 7-10) presenting the results of the parameters, indices, and modules obtained through the FWD measurement have been modified. The clarity with which the formats express the control points for both footprints of the RAP-Geogrid system models has been improved by unifying colors and increasing the size of the markers, in addition to adding some limit bars. Note this in lines 349–350; 384 – 385 and 414 - 415.

5. Structural Framework: The article lacks a clear theoretical framework linking the physical properties of the materials (RAP and geogrid) with the expected performance outcomes. This makes it difficult to interpret the results within a broader context.

A: The research contributes to technical knowledge in the field, providing practical data and observations that can serve as a basis for more detailed future research. The results obtained provide useful statistical information on the behavior of materials under specific conditions. Furthermore, the study has significant practical value, as it demonstrates the feasibility of using RAP and geogrids as a physical interaction system, providing concrete evidence to support the models' performance.

 

1. Title: Lines 1-3 - The title is appropriate, but could be more specific regarding the type of deflection test performed (FWD).

A: The title of the work has been rewritten to reflect the experimental method in lines 2-3.

2. Summary: Lines 17-37 - The summary lacks quantitative information about the experimental design (e.g., sample sizes, specific test conditions) and would benefit from a more precise reporting of key numerical findings.

A: The summary more specifically defines the models as footprints Z1 and Z2, with structural index (SI) values ​​ranging from 0.17 to 0.54 and an extreme difference in dynamic stiffness modulus (DSM) of 10 kN/mm between the models presented. They are described between lines 30 and 32.

3. Introduction: Lines 39-42 - The opening paragraph makes claims about RAP improving sustainability without sufficiently citing or explaining the mechanisms by which this occurs.

A: New citations are provided that outline some of the mechanisms for achieving sustainability using RAP, in addition to expressing the characteristics that RAP exerts on the pavement. Note lines 42 and 43, and 44 and 46.

4. Introduction: Lines 94-96 - The problem statement is delayed until the end of the introduction, weakening the focus of the paper from the beginning.

A: The problem statement between lines 101 – 103 described in this research connects with the paragraph between lines 54 – 56 found earlier in the introduction.

5. Materials: Lines 129-134 - The description of conventional coarse aggregate lacks context to compare these properties to standard specifications or requirements.

A: The properties of conventional coarse aggregate are subject to standard N-CMT-4-04-17 of the Mexican SICT (Mexico City State Consolidated Concrete Institute), as stated in lines 143 and 144. This standard refers to ASTM C33/C33M, which requires adequate particle size distribution; ASTM C127, which specifies a relative density of gravel of 2.90, exceeding the minimum required. ASTM C13, which specifies an average wear loss of 14%, is slightly higher than the normal limits.

6. Materials: Lines 149-153 - Specifications for fiberglass geogrid are incomplete. Critical properties such as aperture size, bonding efficiency, and tensile modulus are not provided.

A: The mesh opening size is expressed on line 165; the bond efficiency is 90% of its intrinsic strength with a tensile modulus of 30 MPa, as indicated on line 167.

7. Figure 2: Line 156: The image of the fiberglass geogrid lacks the scale and detail necessary to understand its structure and integration with the asphalt.

A: The image of the geogrid was changed to one that shows a better understanding scale of its integration with the asphalt and its dimensions on line 171 to 172.

8. Methods: Lines 182-191: The description of the Marshall method lacks details on compaction effort, sample preparation, and test temperature, which are critical variables.

A: The Marshall method expresses viscosity for a given compaction energy and test temperature; it also includes a description of sample preparation based on the M·MMP·4·05·034/23 manual cited between lines 190 and 194.

9. Table 1: Line 189: The table presents data without margins of error or statistical measures, making it impossible to evaluate the reliability of the data.

A: Table 1 is linked to the statistics and shows the error margins for the Marshall design properties of asphalt mixtures. It is located between lines 198 and 199.

10. Figure 4: Line 196: The stability graph shows trends inconsistent with the RAP content that are not adequately explained in the text.

A: The inconsistent trends in Marshall stability reflect a delicate balance between the amount of asphalt cement and the RAP content. Up to approximately 4.0% asphalt cement, stability increases due to the mixture's strong cohesion. However, with increasing RAP content, the mixture becomes softer because the aged asphalt increases, not providing interaggregate bonding. This is explained by lines 214–218.

11. Figure 5: Line 203: Flow results show worrying trends with higher RAP contents exceeding specification limits, but the implications are not discussed.

A: The paragraph discussing flow results for mix designs has been added, taking into account the specification limit they exceed and its consequences in terms of permanent deformation. It is located between lines 226 and 230.  

12. Diagram 3: Line 223: The elastic rebound deflection basin diagram lacks proper axis labels and units, which reduces its interpretation.

A: Diagram 3 has been modified with labels for the axes with corresponding units between lines 252 – 253.

13. Results: Lines 229-233: The results section begins with vague statements rather than presenting specific findings. The use of clear topic sentences would improve readability.

A: The paragraph beginning the results section has been modified with specific findings regarding maximum deflection measurements that identify the first control point for Z1 and Z2 as the most susceptible to permanent deformation. This is found between lines 263 and 265.

14. Equation 1: Line 292: The equation for the normalized area lacks an adequate explanation of variables and units, and its theoretical importance is not adequately discussed.

A: Equation (1) is taken from Hoffman Mario S. Direct method for the evaluation of structural requirements of flexible pavements based on deflections with the impact deflectometer (FWD). YONA Engineering Consulting and Management Ltd. Israel. The units are written and their theoretical significance is explained between lines 337–341.

15. Figure 8: Line 300: The figure plotting normalized area versus maximum deflection lacks a clear delineation between the Z1 and Z2 data points, making visual comparison difficult.

A: The figure 8 now is figure 10 correlating normalized area versus maximum deflection has been improved so that the Z1 and Z2 points can be easily compared visually. Note the line between 346 and 348.

16. Structural Index: Lines 306-313: The explanation of the structural index is inconsistent with the mathematical formulation provided in Equation 2, leading to confusion.

A: The explanation of the structural index has been revised by modifying equation 2 to better understand its application. Note the line between lines 377 and 380.

17. Figure 9: Line 328: The structural index figure uses a color code without a clear explanation in the title, making interpretation difficult.

A: The colors in the structural index, now figure 11 were intended only to make it more visually appealing; however, they complicated its interpretation, so it was unified into a background color with the separation of the rehabilitation levels proposed by Orozco, V. 2005, between lines 384 and 385.

18. Dynamic Stiffness Modulus: Lines 338-346: The description lacks an adequate theoretical context to explain why DSM is an important parameter in pavement evaluation.

A: The importance of the dynamic stiffness modulus in pavement evaluation was explained in a relevant theoretical context. This is explained in lines 401–404.

19. Figure 10: Line 349: The dynamic stiffness modulus graph lacks error bars and statistical analysis, making it difficult to assess the significance of differences.

A: The dynamic stiffness modulus graph has been improved, allowing for a better view of the differences in data dispersion. Note the graph now is figure 12 between lines 414 and 415.

20. Discussion: Lines 357-396: The discussion largely reiterates the results without elaborating or connecting the findings to the broader literature on RAP and geogrid reinforcement.

A: The discussion was reformulated to connect with the findings of the structural index and the dynamic stiffness modulus, considering the theoretical implications of previous studies. It is found between lines 425-428 and 433-440. 

21. Discussion: Lines 385-396: The paragraph on dynamic stiffness modulus does not relate the findings to practical implications for pavement design or maintenance.

A: The findings on the dynamic stiffness modulus have been related to practical implications for the design and maintenance of pavements between lines 467 – 472 and 449 – 453.

22. Conclusions: Lines 397-407: The conclusions state "improvements" without quantifying the magnitude or statistical significance of these.

A: The conclusions now refer to an advantage of the RAP – Geogrid system with respect to a pavement that does not work with this physical interaction of elements between lines 477 – 488.

23. Limitations: Lines 408-421: The article does not address critical limitations related to the small sample size and limited testing conditions.
    A: The sample size and test conditions reflected a full-scale test model that allowed for continuous, controlled traffic flow on the tracks under normal operating conditions. This reinforces the conclusions drawn between lines 489 and 494.
24. Conclusions: Lines 422-434: The last paragraph makes strong claims about the effectiveness of the methodology without acknowledging the preliminary nature of the findings, given the limited data set.

A: It is recognized throughout the study that the amount of data provides a specific perspective on the structural performance of the preliminary findings, which contributed parameters that were correlated to generate methodological certainty. This argument is found between lines 495–501; 214–218; and 312–315.

25. References: Several recent and relevant studies on geogrid reinforcement in asphalt pavements are missing from the literature review.

A: Recent and relevant studies on geogrid reinforcement in pavements have been added. These studies can be found between lines 92–94; 120–122; and 177–179.

26. Scheme 1: Lines 113-127: The model footprint diagrams lack detailed dimensions and material specifications necessary for replication.

A: Diagram 1 shows the widths of the constituent layers, the location of the geogrid is shown between lines 133 - 134, and the dimensions of the footprints for the models are described between lines 122 - 124. The material is explained between lines 124 - 131.

27. RAP material: Lines 138-145: The description of the extraction and processing of RAP material lacks details on aging conditions and extraction efficiency.

A: Line 151 expresses the percentage of aged binder that was successfully obtained by centrifuge extraction in samples of 710 g per load.

28. Methods: Lines 204-208: The description of the deflection test procedure lacks information on temperature control and preconditioning of the test section.

A: The ambient temperature was recorded and the test section was pre-conditioned citing standard N·CSV·CAR·1·03·010/17 between lines 238 – 239.

29. Temperature Correction: Lines 255-264: The description of the temperature correction methodology lacks justification for the selected normalization temperature (20 °C).

A: Normalized deflections were adjusted for temperature according to M·MMP·4·07·020/17, as explained between lines 306 – 307.

30. Future Research: Lines 435-436: The document ends with a vague call for future research without specifying critical knowledge gaps that need to be addressed.

A: Topics from the field have been added that may be needed to fill knowledge gaps in future research. This is found between lines 487–488 and 507–512.

 

The manuscript exhibits significant linguistic deficiencies that impede clear communication of research findings. Throughout the text, inconsistent use of technical terminology is evident, leading to confusion for readers trying to understand the experimental procedures and results. The article exhibits sentence structural problems, with frequent run-on sentences, especially in the introduction and methodology sections, in addition to problematic subject-verb agreement in complex constructions. Verb tense consistency is a persistent problem, with inappropriate shifts between the present and past tense in sections describing similar activities. Excessive use of the passive voice diminishes clarity and immediacy, often obscuring the responsibility for specific research actions. Paragraph organization is frequently problematic, presenting multiple ideas without clear topic sentences or logical transitions between concepts. Conventions of technical writing are inconsistently applied, as evidenced by the variable presentation of numerical data, the inconsistent separation of compound terms, and the irregular formatting of equations and their associated variables. The figure legends lack the detail necessary for independent interpretation, forcing readers to seek explanatory information in the main text. The manuscript also displays imprecise use of language, employing qualitative descriptors where quantitative measurements would be more appropriate, and overusing evasive and cautious language that weakens the presentation of the findings. Inconsistencies in the formatting of citations and references further impair the professional presentation of the article. These linguistic issues, taken together, diminish the scientific impact of the research by creating unnecessary barriers to understanding. A thorough review of the language, focusing on technical accuracy, sentence structure, and adherence to scientific writing conventions, would significantly improve the clarity and accessibility of the manuscript for the intended audience.

A: A thorough and detailed review of the manuscript was conducted, in which I corrected and refined all the aspects noted. Regarding linguistic deficiencies, the clarity and precision of the language were significantly improved, ensuring correct and consistent use of technical terminology. Sentences were restructured to avoid long and complex constructions and are now clear and direct, especially in the introduction and methodology sections. Furthermore, subject-verb agreement and consistency in the use of verb tenses were adjusted, ensuring a uniform and understandable narrative. Paragraph organization was optimized through the introduction of clear topic sentences and logical transitions between ideas, facilitating a fluid and coherent reading. Regarding technical writing conventions, the presentation of numerical data, compound terms, equations, and variables was standardized, following international standards and relevant style guides. Figure captions now contain sufficient and detailed information, allowing for independent interpretation and facilitating a visual understanding of the results. The language was also refined, eliminating inappropriate qualitative descriptors and employing precise quantitative measures that strengthen the argumentation and presentation of the findings.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript is related to pavement sustainability, investigating the application of asphalt pavement composed of reclaimed asphalt pavement (RAP) and fiberglass geogrids. Although the topic is current, the study misses a robust methodological frame. The following are some observations on the subject matter:

1. A main issue is that fiberglass geogrids are typically used in road pavements when there is a need for reinforcement or/and crack control. In this case, authors integrated geogrids into new asphalt layers, which it is of little/useless practical value.
2. In research methodology, the selection of three strategic points (lines 204-205) is not well-explained.
3. In sections 3.1 and 3.2, the normalization process is not well defined, in order the results of this study to be properly evaluated. Especially, in section 3.2, Equations 2 and 3 are not well documented.
4. There is not a clear comparison of the results for both pavement structures.
5. Most importantly, authors state that “the combination of RAP …. efficient rehabilitation system for light traffic roads.” (lines 106-108), which is not eventually proved throughout the research process of this study, as the constructed pavement structures (test tracks) are only composed of RAP and there is not a pavement structure (test track) composed of conventional materials to be used as a reference test track.

 

Author Response

Reviewer 3

 

This manuscript is related to sidewalk sustainability, investigating the application of asphalt sidewalks composed of regenerated asphalt pavement (RAP) and fiberglass geogrids. Although the topic is current, the study lacks a robust methodological framework. Below are some observations on the subject:

1. A major issue is that fiberglass geogrids are typically used in road pavements when there is a need for reinforcement and/or crack control. In this case, the authors integrated geogrids into new asphalt layers, which is of little or no practical value.

A: In the present study, the incorporation of un-asphalt fiberglass geogrid in the structure of the rolling bed for a sample of a full-scale model aims to evaluate the implications of the physical interaction of the compound through its integral performance in normal traffic operation situation with vehicles that do not exceed 3.5 tons, which are the bulk of urban roads, where recycled asphalt pavement is a recycled material that, due to its heterogeneity and aged binder conditions, is susceptible to inconsistencies in the stiffness of the rolling beds, as observed in the graph between lines 221 - 222, but the reinforcement without additional bitumen shows progress in its support capacity and resistance to permanent deformation.

1. In research methodology, the selection of three strategic points (lines 204-205) are not well explained.

A: The experimental area was designated at the vehicle access to the graduate parking lot of the Faculty of Construction and Habitat Engineering at the University of Veracruz. This ensures continuous traffic flow on the model. Therefore, based on the various distances between vehicle axles, a pair of tracks were drawn that span the access lane, allowing for the unloading of one vehicle axle symmetrically distributed across the tires. In each of them, as in the figure for lines 240-241, three control points are located in one, defined by the access direction from the center to the right and left, generating a diagonal that allows for rolling each time a vehicle enters between lines 235-236.

1. In sections 3.1 and 3.2, the normalization process is not well defined, in order for the results of this study to be appropriately evaluated. In particular, in section 3.2, equations 2 and 3 are not evaluated. Well documented.

A: Sections 3.1 and 3.2 have been redefined, adding new details that improve the interpretation of the results. The definition and units of the equations, particularly equation 2, have also been adjusted, integrating equation 3 into the equation to ensure its evaluation is relevant. Note the line between lines 377 and 380.

1. It is not clear to compare the results for both sidewalk structures.

A: The graph axis scales were modified by increasing the size of the markers, standardizing the color codes, and adding some details to make comparing the Z1 and Z2 footprints more agile. This can be seen in lines 346–347, 381–382, and 411–413.

 

 

1. It is important to note that the authors state that “the combination of RAP…. efficient rehabilitation system for light traffic roadways.” (lines 106-108), which is not eventually tested throughout the research process of this study, as the constructed sidewalk structures (test tracks) are only composed of RAP and there is not a pavement structure (test track) composed of conventional materials to be used as a reference test track.

A: The incorporation of RAP (reclaimed asphalt pavement) into asphalt mixtures, combined with the use of a fiberglass geogrid, represents an innovative and sustainable strategy for improving the strength and durability of pavements designed for vehicular traffic weighing less than 3.5 tons in experimental areas. The interaction between RAP and the fiberglass geogrid favors a significant improvement in the structural rigidity and resilience of the pavement, since the RAP, when reused and crushed, provides aggregates and rejuvenated asphalt binder that increase internal cohesion and resistance to permanent deformation. Furthermore, the fiberglass geogrid acts as reinforcement that distributes load stresses, minimizing crack propagation and facilitating deflection recovery after loading, which is essential for prolonging pavement life under moderate traffic conditions. The synergy between these materials has been shown to improve the structure's resilience to repeated loads, maintaining deflection levels, contributing to an efficient solution for light-traffic pavements. Changes were made to lines 62–64, 66–68, 74–75, 81–83, 92–94, and 109.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

General Comments

1. The manuscript addresses a relevant and timely topic in sustainable pavement engineering by investigating the structural response of RAP pavements reinforced with fiberglass geogrids using deflection-based testing.
2. The methodology is generally outlined but lacks clarity and scientific precision in many aspects. The rationale for some design choices remains unexplained, particularly in the experimental design and model scale.
3. Figures and tables are not uniformly presented; there is inconsistency in formatting, caption clarity, and technical details.
4. There is a heavy reliance on descriptive reporting of results without sufficient analytical depth or interpretation linked to engineering principles or prior research.
5. The discussion and conclusion sections are repetitive and tend to overstate findings based on limited data.
6. Plots and artworks are poor quality, better tools should be used to create the plots, such as Sigma plot. All photos are not the proper scale and misalignment.

 

Specific comments

• Lines 2–3: The title is vague. It should reflect the experimental method (e.g., FWD), the RAP content, and the use of geogrid more precisely.
• Lines 17–19: The phrase “elastic rebound in the pavement layers” is imprecise. Use standard terms such as “recoverable deflection” or “elastic deflection.”
• Lines 24–25: “Normalized maximum deflection” is unclear; definition or reference is needed.
• Lines 27–29: The structural index values provided do not show a consistent improvement due to reinforcement. No statistical significance is discussed. Further literature review on geosynthetics and full-scale test section should be include., i.e. https://doi.org/10.1016/j.geotexmem.2018.12.012, https://doi.org/10.1007/s42947-024-00447-7,
• Finite element should be included, the authors should also refer to this full-scale study with advanced FEA., https://wjst.wu.ac.th/index.php/wjst/article/view/10731.
• Line 34: The claim that the modulus “indicates the improvement of the structural integrity” is not fully supported by data or analysis.
• Line 40: The sustainability benefit of RAP is stated but lacks a quantitative or referenced comparison.
• Lines 43–45: The phrase “structural fragility” is vague and lacks technical definition.
• Lines 55–59: Listing geosynthetics without discussing selection criteria or mechanisms is superficial.
• Line 69: The statement that RAP can be used “when a lower asphalt content is needed” is ambiguous and unsupported.
• Lines 77–78: “Enhanced, sustainable pavement lifespan” is too broad and unqualified.
• Line 112: The 1 m² test structure is unrepresentative of field conditions; no justification is given for this scale.
• Line 115: No rationale is provided for placing the geogrid at the centre of the asphalt layer.
• Lines 130–133: Aggregate properties are reported, but no standards or comparison to specifications are included.
• Line 137: The term “Cleveland flash point” is used incorrectly; it should be “Cleveland open cup flash point.”
• Lines 139–141: Gradation of RAP is described, but no sieve analysis or graphical data are included.
• Line 150: Tensile strength unit “N/cm²” is non-standard; use MPa.
• Line 153: The geogrid’s 15-year service life claim is accepted without verification or testing context.
• Line 162: The FWD device is introduced without specifications or model justification.
• Line 168: Sensor spacing should include justification based on typical deflection basin width.
• Line 182: No mention of number of repetitions per load or location, which affects data reliability.
• Lines 188–190: Table 1 shows RAP content effects, but no discussion of statistical variation is included.
• ine 199: The threshold of 4 mm for deformation is cited but not connected to pavement failure mechanisms.
• Lines 230–232: “Elastic rebound” terminology is used imprecisely. Should clarify with a standard term.
• Line 238: “Constant stress of 700 kPa” requires citation and explanation of its significance.
• Line 243: The use of interpolation and extrapolation is described but not validated with error margins or justification.
• Line 255: Temperature correction methodology is referenced but not detailed.
• Line 267: “Rolling surface of the experimental area” is unclear; rephrase for clarity.
• Line 273: Acceptable/unacceptable range of 0.40 mm lacks source or context.
• Line 285: Equation (1) lacks units and derivation; its origin is not cited.
• Line 306: The explanation of the Structural Index lacks discussion of its limitations or sensitivity.
• Line 322: Equation (2) and (3) are presented without adequate definition of parameters.

 

• Line 343: Equation (4) lacks explanation of terms (e.g., FD), and units are not clearly stated.
• Line 357: Discussion merely restates results without linking to prior studies or theoretical implications.
• Line 366: The effect of “thermal variations” is referenced without analysis or quantitative consideration.
• Line 374: “Better mechanical properties” is vague and should be technically specified.
• Line 381: “Urgent need for attention” is an overstatement without supporting evidence.
• Line 398: “Influenced by the support conditions of the base layer” is generic; specific finings should be cited.
• Line 403: The term “promising structural condition” is ambiguous and unmeasured.
• Lines 408–413: Climate effects are acknowledged, but no experimental consideration is included in the study.
• Line 418: “Weak structure on a weak subgrade” needs quantification or reference threshold.
• Line 433: The “gap between model footprints is minimal” contradicts earlier claims of performance difference.

 

Comments on the Quality of English Language

The manuscript requires professional English editing to meet publication standards. Ideally, a native English-speaking editor with technical expertise in civil or pavement engineering should revise the text for grammar, style, and clarity.

Author Response

Reviewer 4

 

General comments

1. The manuscript addresses a relevant and timely topic in sustainable sidewalk engineering by investigating the structural response of RAP pavements reinforced with fiberglass geogrids using deflection-based testing.

A: Recoverable reflection is an effect that was decided to work on in this research because it is not a destructive test that allows the structure of the flexible pavement layers to be qualified, with special interest in the tread layer that contains 30% RAP.

1. The methodology is generally outlined but lacks clarity and scientific precision in many aspects. The fundamental reason for some design choices remains inexplicable, particularly in the experimental design and model scale.

A: The experimental area was designated at the vehicle access to the graduate parking lot of the Faculty of Construction and Habitat Engineering at the University of Veracruz. This ensures a continuous flow of traffic on the model. Therefore, based on the various distances between vehicle axles, a pair of tracks were drawn that span the access lane, allowing for unloading of one vehicle axle symmetrically distributed across the tires. The model is for a small section of a full-scale experimental model.

1. Figures and tables are not uniformly presented; there is inconsistency in format, title clarity, and technical details.

A: The figures and tables were reworked to ensure they had a uniform format, as well as the titles and technical details.

1. There is a heavy reliance on descriptive reporting of results without sufficient analytical depth or interpretation linked to engineering principles or prior research.

A: Greater depth was written on the results reports with references to other studies that led to technical coincidences with the opportunity for analytical interpretation.

1. The discussion and conclusion sections are repetitive and tend to...overstate recommendations based on limited data.

A: The discussion and conclusion sections were rewritten to express recommendations consistent with the research results.

1. The plots and illustrations are poor quality; better tools should be used to create the graphs, such as the Sigma chart. All photos are not scaled properly and are misaligned.

A: The graphical details that presented the organization of the data have been fixed, making the scale and alignment uniform.

 

Specific comments

• Lines 2–3: The title is vague. It should reflect the experimental method (e.g., FWD), RAP content, and geogrid use more accurately.

A: The title of the work has been rewritten to reflect the experimental method in lines 2-3.

• Lines 17–19: The phrase “elastic rebound on the sidewalk layers” is imprecise. Use standard terms such as “recoverable deflection” or “elastic deflection.”

A: The term “elastic rebound” has been changed to “recoverable deflection” in the sentence between lines 19 – 20.

• Lines 24-25: “Normalized maximum deviation” is unclear; definition or reference is needed.

R: Added definition of normalized maximum deflection on line 25.

• Lines 27–29: The structural index values ​​provided no improvement in slope consistency to reinforcement. No statistical significance is discussed. Further literature review on geosynthetics and full-scale test sections should be included, i.e., https://doi.org/10.1016/j.geotexmem.2018.12.012,https://doi.org/10.1007/s42947-024-00447-7,

A: A paragraph was included between lines 90 – 92 with the proposed reference on geosynthetic configurations in full-scale tests that are appropriate for the contribution of this work, and the proposed reference that allows talking about sections smaller than the full-scale experimental areas was added between lines 120 – 122.

• Finite Element Should be included The authors should also refer to This full scale study with advanced FEA .,https://wjst.wu.ac.th/index.php/wjst/article/view/10731.

A paragraph of the suggested reference was added between lines 177 – 178.

Line 34: The claim that the module “indicates the improvement of the structural integrity” is not fully supported by data or analysis.

A: In Figure 12, between lines 415 and 417, it can be seen that the dispersion of the values ​​obtained for footprint Z1 is closer to limit no. 02 compared to the values ​​for footprint Z2. Therefore, the term "improvement" was changed to "stability" on line 35.             

• Line 40: The sustainability benefit of RAP is fixed but lacks a quantitative or referenced comparison.

A: Text referring to the benefit of RAP sustainability was added based on a new author's study between lines 42 and 43.

• Lines 43–45: The phrase “structural fragility” is vague and meaningless. technical definition .

A: The phrase “structural fragility” was rewritten between lines 44 – 46 due to the technical definition that subsequently connects with the use of FWD in the present work.

• Lines 55–59: Listing of geosynthetics without discussing selection criteria or mechanisms is superficial

A: More details have been provided on the geogrid selection criteria, as well as the selection criteria for their application to pavements between lines 62 and 71.

• Line 69: The statement that RAP can be used “when a lower level asphalt content is “necessary” is ambiguous and unsubstantiated.

A: The sentence was rewritten based on the literature it referenced to eliminate the indicated ambiguity. See lines 73–75.

• Lines 77–78: “Improved, sustainable sidewalk "lifespan" is also broad and unreserved

A: The statement on the contribution of the elements that interact with the pavement was limited and more precisely defined between lines 81 – 83.

• Line 112: The 1 m² test structure is not representative of field conditions; no justification is given for this scale.
• RThe choice of 1 m² for each footprint model in the deflection measurements reflects accessibility and structural monitoring accuracy. This size guarantees a representative value for detecting variations in structural deformation without compromising the environment where the model was built, as it fits within the physical dimensions of the available space in the building. Furthermore, by maintaining a surface in the lane, a measurable and controlled traffic flow is ensured. The vehicle's tires therefore always roll on both surfaces, allowing for consistent and repeatable deflection measurement based on the vehicle's dynamic behavior on the axles, without external interference. This justification was written between lines 119 and 124.
• Line 115: No justification is provided for placing the geogrid in the center of the asphalt layer.

A: The wearing course, the surface subjected to dynamic loads and variable environmental conditions, is susceptible to cracks propagating from lower layers due to the laying process. The fiberglass geogrid acts as reinforcement that distributes stresses. To place it at the center of the layer, a previous work is cited in line 109 that explains the RAP-Geogrid system applied in this work. In this work, a point load test was performed on specimens made with the same mixture as the wearing course, placing the fiberglass geogrid in three positions relative to their height. The one that performed best was when the geogrid was placed at the center.

• Lines 130–133: Added Properties are reported, but no standards or comparison to specifications are included.

A: The results obtained for conventional aggregate are subject to standard N-CMT-4-04-17 of the Mexican SICT (Mexico City State Institute of Cement Industry) expressed in lines 143 and 144. This standard refers to the ASTM C33/C33M standards, which require adequate particle size distribution; ASTM C127, which specifies a relative density of gravel of 2.90, exceeding the minimum required. ASTM C13, which refers to an average wear loss of 14%, is slightly higher than the usual limits.

• Line 137: The term "Cleveland flash" dot" is used incorrectly; it should be "Cleveland Open Cup flash" dot."

A: The term “Cleveland flash” has been changed to the suggested term “Cleveland open cup flash point” between lines 146 – 147.

• Lines 139–141: RAP gradation is described, but no sieve analysis or graphical data is included.

A graph showing material gradation has been added between lines 160 and 161.

• Line 150: Tensile strength The unit “N/cm²” is not standard; use MPa.

A: The unit “N/cm²” has been changed to “MPa” in line 164.

• Line 153: The 15-year geogrid service life claim is accepted without verification or context testing.

A: Fiberglass geogrid has a 15-year lifespan due to its high resistance to corrosion, stability in humid environments, climate changes, and its ability to maintain mechanical properties over time. This information was written between lines 166 and 167 and was obtained from the Ecomex technical data sheet, which suggested using the non-asphalt byproduct (not for sale).

• Line 162: The FWD device is entered without budget or model justification.

A: The Dropped Weight Deflectometer (FWD) is an integral part of the pavement structural assessment process and a rapid, non-destructive method for evaluating the structural capacity of pavements, used in this investigation. This equipment was assisted by YUTAVE Engineering in collaboration with the Universidad Veracruzana. The FWD is described by adding key operational characteristics between lines 172 to 174 and its physical characteristics are found between lines 178 and 179. The technical sheet can be found at https://dynatest.com/wp-content/uploads/2022/09/FWD-4-pages-brochure-A4.pdf

• Line 168: Sensor spacing should include justification based on typical basin width deviation.

A: The deflection basin width, considering the spacing and distribution of the sensors at 0, 300, 450, 600, 900, 1200 and 1800 mm (see diagram 3 between lines 252 to 253, which are values ​​fixed to the equipment chassis), is achieved in the range of 600 to 1200 mm. This range reflects the area in which the structure experiences the greatest deformation detected by the sensors, being an estimate based on the given distribution.

• Line 182: No mention of number of repetitions per load or location, which affects the reliability of the data.

A: On line 237, a series of impacts equal to 8 was specified. This is due to the reproducibility criterion where the first and second impacts must not have a difference in the record greater than 3%.

• Lines 188–190: Table 1 shows the content of RAP effects, but no discussion of statistical variation is included.

A: The discussion on the effects of RAP was written between lines 201 – 211.

• Year 199: The 4 mm limit for deformation is cited but not connected to sidewalk failure mechanisms.

A: If the mix exceeds 4 mm of Marshall flow, it indicates low mix density and compaction, which in turn reduces the strength and durability of the pavement. It also facilitates the penetration of water and aggressive agents, increasing the risk of premature deterioration, deformation, and failure of the road structure. The explanation can be found between lines 224 and 227.

• Lines 230–232: “Elastic rebound terminology is used imprecisely. I should clarify with a standard term.

A: The standard term was chosen as “Recoverable deflection” and can be read on lines 19 – 20,  254.

• Line 238: “A constant tension of 700 kPa” requires citation and explanation of its importance.

A: The value of 700 kPa is applied based on the SICT FWD test procedures manual M·MMP·4·07·020/17 and the reason for this value is explained as a reference between lines 271 - 274.

• Line 243: The use of interpolation and extrapolation is described but not validated with margins of error or justification.

A: Between lines 279 to 284 the use of the method is justified more precisely.

• Line 255: Temperature correction methodology is referenced but not detailed.

A: The methodology for temperature correction is complemented by the graph in standard M·MMP·4·07·020/17 between lines 306 to 307.

• Line 267: “Experimental area rolling surface” is unclear; rephrase for clarity
• A: Between lines 312 – 315 it was clearly written that this is the tread layer of the Z1 and Z2 footprint models in the experimental area.
• Line 273: Acceptable/unacceptable range 0.40mm missing source or context.

A: The acceptable range indicates that a road segment, in this case the homogeneous areas, is representative due to a good structural condition and is based on table 1 of N∙CSV∙ CAR∙1∙03∙010/17 cited on line 321.

• Line 285: Equation (1) lacks units and derivation; its source is not cited.

A: Equation (1) is taken from Hoffman Mario S. Direct method for the evaluation of the structural needs of flexible pavements based on deflections with the impact deflectometer (FWD). The units and their designations are written. Note the values ​​between lines 337 and 341.

• Line 306: The explanation of the Structural Index lacks discussion of its limitations or sensitivity.

A: A discussion about the limitations of the structural index has been written between lines 364 – 370.

• Line 322: Equations (2) and (3) are presented without adequate parameter definition.

A: Equations (2) and (3) were merged into equation (2) and their units are written and their parameters defined between lines 377 – 380.

• Line 343: Equation (4) lacks explanation of terms (e.g., FD) and units are not clearly stated.

A: Equation (4) is now (3) write its units and define its terms between lines 406 – 409.

• Line 357: Discussion merely restates results without link to previous studies or theoretical implications.

A: The discussion of the results between lines 425 - 430 was modified to consider their theoretical implications. 

• Line 366: The effect of “thermal variations” is referenced without analysis or quantitative consideration.

A: The term “thermal variations” has been removed from the study because there is no data available to analyze their impact on deflection recording.

• Line 374: “Best mechanical properties” is vague and should be technically specified.

A: The best mechanical property is the resistance to permanent deformation which is written between lines 437-440.

• Line 381: “Urgent need for attention” is an exaggeration without secondary evidence.

A: The statement about the evidence shown in Figure 9 has been reworded so that it doesn't appear exaggerated. It can be read on line 443.

• Line 398: “Influenced by base layer support conditions” is generic; specific clarifications should be cited.

A: The argument between lines 478 – 479 was restated with more concrete terms regarding the structural index of the conclusion with the relevant citation.

• Line 403: The term "promising" structural condition" is ambiguous and overstated.

A: The term “promising structural condition” has been modified to more accurately express the expectation. See line 486.

• Lines 408–413: Climate The effects are acknowledged, but no experimental considerations are included in the study.

A: The word climate and its effects were removed because in this study, specifically in the conclusions section, no data was recorded for analysis. 

• Line 418: “Weak structure in a weak subgrade needs quantification or reference limit.

A: For the load classification of the subgrade and structure, the dynamic rigidity modulus result from Figure 12 was used, where all control points are less than 50 kN/mm2. Note the values ​​between lines 491 and 492.

• Line 433: The “gap between model footprints is minimal” contradicts earlier claims of performance difference.

A: The sentence containing the argument about the minimal gap difference between the footprint models was removed because it contradicts previous statements about performance differences.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have modified the article following the comments. Therefore, the article has been improved and can be published. Some sections cannot be improved.

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript titled "Structural evaluation with FWD of asphalt pavement with 30% of RAP reinforced with fiberglass geogrid in the asphalt layer" presents a well-structured experimental study that makes a valuable contribution to sustainable pavement engineering. Upon re-review, I find that the authors have successfully addressed the previous concerns and the manuscript now meets the publication standards.

Reviewer 3 Report

Comments and Suggestions for Authors

Authors made some additions to the manuscript. However, they didn't succeed to:

1. enhance their statement about the combination of RAP and geogrids

2. explain thoroughly the strategic points in their in-situ test and the position of FWD device on the experimental area 

3. adequately define the normalization process used in their research analysis

4. explain the evaluation and comparison process of both tested models

5. enhance the objectives of their study (lines 114-117).

Reviewer 4 Report

Comments and Suggestions for Authors

The authors have addressed the reviewer' comments and it can be accepted in the current form.