Rebound Effect Generated by Waste HDPE in Hot Asphalt Mixtures

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper is well done. However, you mention it is far known effect (the rebound with dry process)

However, the paper is relevant and interesting to the topic of journal

revised some note to did to you and correct one part is in Spanish.  

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Some part of text is in Spanish. must be translated

Author Response

Comment 1:

[Not meet the specification? What shows the properties at 70 if it is a PG 64?]

Response 1:

[Thank you for pointing this out. We agree with the comment. The issue was caused by a transcription error in the table presenting the results of the rheological properties test. We have corrected this by fully updating the table and including the appropriate data to accurately identify the type of asphalt used (PG 64), in accordance with AASHTO T315 Standard. ]

[The change can be found on Page 3, Table 2: “Rheological Properties of PG 64 Binder according to AASHTO T315 Standard.]

Comment 2:

[Why improve durability? How you measure this to state that?]

Response 2:

[Thank you for pointing this out. We agree with the reviewer’s comment. We have revised the text to clarify that the term “durability” was not the most appropriate in this context. What was actually observed was better initial structural resistance and cohesion of the 0.62% HDPE mixture during the compaction process.

Therefore, we have modified the description in Table 7 (page 6) by replacing “improved durability” with “improved cohesion”, as this term more accurately reflects the experimental observation. It is important to note that no specific durability tests (such as aging or long-term performance assessments) were carried out in this study.]

[The change can be found on Page 6, Table 7. Compaction Results of Asphalt Mixes]

Comment 3:

[This part is in spanish. Translate]

Response 3:

[Thank you for pointing this out. We agree with the reviewer’s comment. The section in question was originally in Spanish by mistake. We have corrected the text, and it is now fully translated into English. ]

Thank you for pointing this out. We agree with this comment. Therefore, we have properly translated the paragraph.

[This correction can be found on page 7, lines 222–226.]

[Updated text in the manuscript:

“In the mixtures containing 1%, 4%, and 5% HDPE, no valid results were obtained due to cohesion issues and the rebound effect—a phenomenon previously documented in studies on the use of plastic polymers in asphalt mixture [15], [35]. This behavior hindered compaction and altered volumetric properties, revealing a lack of internal cohesion that compromises practical feasibility.”]

Reviewer 2 Report

Comments and Suggestions for Authors

The article presents the results of research on the use of polyethylene (HDPE) waste for the production of asphalt pavements. The rheological properties of asphalt mixtures were assessed on the basis of rheological tests (dynamic shear rheometer) and rutting using the so-called Hamburg Wheel. It was shown that HDPE waste cannot be present in the mixture in excess of 1% due to its elastic properties (the so-called Poisson effect). A smaller amount of HDPE improves compaction by better packing of grains. The system's ability to plastically deform also increases, as indicated by the Hamburg Wheel test. This is probably related to the adhesion of plastic to the asphalt binder. The presented research is clearly aimed at application purposes, although the increased possibility of microplastic emission has been forgotten. Asphalt roads with the addition of HDPE are particularly "privileged" in this respect. However, these studies have not been presented. The article was edited correctly, but lines 211-215 were forgotten.

Comments on the Quality of English Language

Not everything is translated correctly.

Author Response

Comment 1:

[The system's ability to plastically deform also increases, as indicated by the Hamburg Wheel test. This is probably related to the adhesion of plastic to the asphalt binder. The presented research is clearly aimed at application purposes, although the increased possibility of microplastic emission has been forgotten. Asphalt roads with the addition of HDPE are particularly "privileged" in this respect. However, these studies have not been presented.]

Response 1:

[Thank you for pointing this out. We agree with the reviewer’s comment. We acknowledge that the potential release of microplastics was not evaluated in the present study, as the main focus was to analyze the mechanical and rheological properties of HDPE-modified mixtures. However, we consider this an important environmental concern, and therefore, we have included a brief review of recent literature that highlights this issue.

As a result, we have added a specific paragraph in the introduction (page 2, lines 45–50) and another in the conclusion section (page 10, lines 331–334) to acknowledge this limitation and highlight it as a relevant future line of research.]

 [This correction can be found on page 2, lines 45–50 and page 10, lines 331–334.]

[Updated text in the manuscript:

Introduction (page 2, lines 45–50):

“Recent studies have shown that pavements modified with plastic waste can act as emitters of microplastics, generated through vehicle traffic friction and material degradation [9]–[11]. These particles, transported by runoff or wind, reach terrestrial and aquatic habitats, where their persistence and potential for contamination raise environmental concerns [12], [13]. This potential emission represents an environmental risk that should be considered in future evaluations. ”

Conclusion section (page 10, lines 331–334):

“Although the present study focused on the mechanical and rheological properties of asphalt mixtures with HDPE addition, it is important to note that the potential release of microplastics due to surface wear was not evaluated. This represents a future line of re-search that is essential to understanding the possible environmental impacts of this technology. ” ]

Comment 2:

[This part is in spanish. Translate]

Response 2:

[Thank you for pointing this out. We agree with the reviewer’s comment. The section in question was originally in Spanish by mistake. We have corrected the text, and it is now fully translated into English. ]

Thank you for pointing this out. We agree with this comment. Therefore, we have properly translated the paragraph.

[This correction can be found on page 7, lines 222–226.]

[Updated text in the manuscript:

“In the mixtures containing 1%, 4%, and 5% HDPE, no valid results were obtained due to cohesion issues and the rebound effect—a phenomenon previously documented in studies on the use of plastic polymers in asphalt mixture [15], [35]. This behavior hindered compaction and altered volumetric properties, revealing a lack of internal cohesion that compromises practical feasibility.”]

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The paper was corrected acording to mi comment. 

I still stand by my statement from the previous review:
The topic is not new or novelty only the part of waste plastic

Reviewer 2 Report

Comments and Suggestions for Authors

After these corrections, the article is suitable for publication.