Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1) Systematic review baseline by PRISMA should be conducted and detailed in the materials and method section, then status of the studies can be discussed, not in the section of introdcution. 

2) what is the importance of rejuvenators in the topic of asphalt ?? please explian in Introduction.

3) What is the available review studies in this field, what is the neccessity/differences compared to other review studies in this field?? Therefore, the introduction should be re-organized by details.

4) The author focused the micro and macro characteristics of the rejuvenating aged asphalt; however, each class can be more detailed, for instance, the micro indicators are not clear, more clear classification and detail literature sumamry by tables can be prepared to evaluate the main and sub classes. The authors, directly examined Surface micro-structure as a micro-indicators without any classicification. Thus, other parameters did not examine and they were ignored by the authors.

5) Moreover, in the macro-indicators, reological characteristics and ductility combined; however, reological properties are mostly related to surface characteristics. Thus, more distict classification and bibliographic background can be added for the micro- and macro-classification.

6) all classification are mixed by types and macro- and micro-properties. therefore, at first, please, a clear classification and subtitles can be conducted and presented by a clear figure and appropriate bibliography. Then, discusses with avialble rstudies using table comparision by scietific details.

7) Conclusion can be re-organized after the findings. Moreover, recommendation, and advantages and limitation of the review can be stated with future needs. 

 

 

Comments on the Quality of English Language

The Englished of the MS should be polished

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

I found this manuscript to be a thorough and timely review of rejuvenators for aged asphalt, especially concerning their classification, micro-level properties, and macro-scale performance. The topic is an important one, given the growing emphasis on sustainable road construction and the push to reuse reclaimed asphalt pavements. Overall, the paper makes a valuable contribution, and here are some suggestions that could make it better.

At times, the review feels more like a list of studies than a critical synthesis of the field. I would encourage the authors to go beyond summarizing and highlight contradictions, trade-offs, and open questions. For instance, bio-based oils are often shown to improve low-temperature flexibility, but they may at the same time reduce rutting resistance. Bringing these kinds of tensions to the forefront would add real depth to the review. Along the same lines, the section on reactive rejuvenators could be presented more clearly if epoxy- and isocyanate-based systems were compared side by side in a simple table. Some parts, especially the section on bio-based rejuvenators, are also quite dense. Breaking them up with subheadings, summary tables, or even a few schematic diagrams could go a long way toward improving readability.

I also think the outlook section could be expanded. Right now is brief, but this is the place where the authors can point toward the future. Mentioning areas like nanomaterials, bio-inspired additives, or even the use of machine learning in mixture design would give the paper a more forward-looking edge. It would also be helpful to discuss some of the practical challenges researchers and engineers face—things like cost, environmental trade-offs, and the lack of standardized testing methods. Including these considerations would make the paper more relevant to both academic and industry readers.

The figures are a useful part of the review, but they would be more effective with consistent formatting and fuller captions that clearly explain what the reader should take away. A summary table comparing rejuvenator types, their mechanisms, strengths, and limitations would also add real value. Finally, the bibliometric analysis is interesting, but it would be stronger with a bit more interpretation—for example, explaining why China and the United States dominate the field, and what opportunities there are for contributions from other regions.

Comments on the Quality of English Language

Here are some minor suggested changes:

• 37 — “As asphalt pavements aging” → “As asphalt pavements age”

• 44 — “When virgin asphalt aged” → “When virgin asphalt ages” 

• 50 — “for different asphalt” → “for different types of asphalt”

• 59, 60, 62, 69, 73 — Add missing spaces after citations:

  • “Shen et al. [14]restored” → “Shen et al. [14] restored”

  • “Cao et al. [15]found” → “… [15] found”

  • “Asli et al. [16]were” → “… [16] were”

  • “Ma et al. [19]restored” → “… [19] restored”

  • “Xu et al. [21]and Cao et al. [22]found” → “… [21] and Cao et al. [22] found”

• 68 — “Additionally, To address” → “Additionally, to address”

• 91 — “providing a strong theoretical foundation for future research and further promoting…” → could shorten to “… providing a foundation that supports future research and advances…”.

• 93 — “that China and the United States status” → “China and the United States’ status”

• 205 — “so they could improve their performance in general” → smoother: “thereby improving overall performance”

• 262 — “[78], et al..” → “et al.”

• 298 — “It could be learned from” → “It can be inferred from”

• 316 — Subheading duplicated: both are “a)”. Change second one to “b) Isocyanate system”

• 376 — “researches … is still” → “research … remains”

• 477 — “They respectively characterized … respectively” → simplify: “They characterized changes in small and large molecules”

The text employs several repetitive phrases and words; consider replacing them or rephrasing the sentences for greater clarity.  For example:

• “Improved / enhance / recovery”-Often repeated in back-to-back sentences.

• Significantly

• Indicates / indicates that

• “Based on …”

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Title:

Application of rejuvenators in rejuvenation of aged asphalt: classification, micro-, and macro-properties

 

- As a suggestion the title of this manuscript could be shortened. “in rejuvenation of aged” is redundant.

For example: “Application of rejuvenators in asphalt binders: classification, micro-, and macro-properties”.

 

Abstract:

- In the entire manuscript, be consistent with the terminology: asphalt, binder, asphalt binder, etc.

 

Introduction:

Line 8 – Fix the capital letter. To address….

Figure 1a and 1b – Please, improve the y-axis label. Both plots are with the same label and its difficult to differentiate them. E.g. 1a - number of published papers and 1b - number of citations of published papers.

Figure 1d – Proportion instead of Proporation. Be consistent in the entire manuscript. Also, as a suggestion China, instead of “Peoples R China”.

 

Classification of rejuvenators:

Figure 3 – What is the meaning of MFC? And GC? Not available in the entire manuscript or initial table of abbreviations at the beginning of the manuscript.

Line 320 – Meaning of HDI? Not available in the entire manuscript or initial table of abbreviations at the beginning of the manuscript.

 

Micro-properties of rejuvenated asphalt:

Line 358 – For formality do not use abbreviations in the Section name. Please, revise the entire document about this.

Line 384 - For formality do not use abbreviations in the Section name. Please, revise the entire document about this.

Line 412 - For formality do not use abbreviations in the Section name. Please, revise the entire document about this.

Line 439 – Define BSI. Definition is not available in the entire manuscript or initial table of abbreviations at the beginning of the manuscript.

Figure 12 – Can you include a label for the y-axis? Molecular wight? Units?

 

Macro-properties of rejuvenated asphalt:

Figure 13 – It’s difficult to understand the abbreviations of the x-axis. It seems that VA = virgin asphalt binder, AA = aged asphalt binder, R = rejuvenated asphalt binder? Why one of the labeling is showing 30%AA? This, is related to WEO and SBS1. I would suggest a better figure label/title: “Penetration of virgin asphalt (VA), aged asphalt (AA), and aged rejuvenated asphalt (RA) at different concentrations”. Do you know the concentration of rejuvenator related to WEO, AO, HDDGE, AO-S, AO, and SBS-S? Please improve this figure labeling and information. Use border line of bars in black color for better visual understanding. When you said aged asphalt binder, what was the method used to aging the binder? Laboratory aged using RTFO plus PAV 100C? 20hours? Etc. Please explain the aging method used.

Figure 14 – Same comments as figure 13.

Line 535 – Ductility not only affects low-temperature cracking. Also, fatigue cracking, block cracking, etc. Please, discuss here in the manuscript.

Figure 15 – Same comments as figure 13.

Line 540 – What is the meaning of WPE?

Line 589 – Good point. Also, this correlates with ductility test.

Figure 16 – Improve the label/title of this figure: b) it should be Performance Index Value? Also c) It should be Fatigue Life or Number of Cycles to Failure? Figure title looks informal. Also, in the y-axis of the plots do not show the abbreviations only, such as, C or Nf. Please indicate the entire name.

Figure 17 – Same comments as before. Figure label/title please indicate he entire name for “m” Creep Rate. Text looks informal. Origin now is the term to refer to virgin binder? Please be consistent in the entire manuscript. What is the meaning of RTFOT? PAV? Etc. Also, I am confused. The Figure 17 title refers to the change of m. Is this the m-value parameter? Slope at 60 seconds? Because, the Figure 17 graph only shows the Stiffness. Please double check and revise the plot and/or the Figure title/label.

Line 618 – after 40 hours of aging in the PAV? Where?

Line 622 - was better than the rejuvenated virgin asphalt.

 

Macro-properties of rejuvenated asphalt mixture:

Figure 18 – Please include in the figure label/title the conditions of the test. Wet, dry condition? At what temperature? 50C? etc. Are these results based on rejuvenators added to 100 % RAP mixture? If that is the case RAP Mix = Control mix? Include this information in the Figure label.

 

Line 726 – What is the meaning of WVO? Please, revisit the entire manuscript to avoid any abbreviations without the definition.

Line733 – TSR what is the meaning of this abbreviation?

 

Technical challenges and future recommendations:

Line 762 – Remove “of researches”.

 

Conclusions:

Line 850 – What is the meaning of AI? Please, revisit the entire manuscript to avoid any abbreviations without the definition.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors mostly revised the article; however, there is a problem in the micro- and macro-properties of the rejuvenated asphalt. There is still an issue; please conduct a clear scheme and a paragraph related to these properties with an appropriate literature background. Moreover, sections and subsections should be arranged. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf