Environmental Performance of Road Asphalts Modified with End-of-Life Hard Plastics and Graphene: Strategies for Improving Sustainability
, Francesca Rosa 2,3 and Paride Mantecca 2,*Round 1
Reviewer 1 Report
In this manuscript, the authors demonstrated an LCA study according to a cradle-to-cradle approach. Various scenarios were compared, e.g., the variability of the pavement's layers thickness and the amount of reclaimed asphalt. The results exhibited that the addition of the modifier enhanced the structural performance of bitumen concretes (BCs), raising the extended durability of the pavement and reducing maintenance cycles. Also, the BC modifier creates a synergistic effect by providing an alternative to hard plastic incineration by using it as secondary raw materials.
The literature is well-described, making readers understand a brief studying history of this field.
The research methods are well-described. The analysis was performed by LCA methodology according to ISO 14040 and 14044 which consists of four interconnected phases: goal and scope definition, inventory analysis, impact assessment, and interpretation.
In summary, the manuscript can be published after minor revision.
Some minor suggestions are listed below.
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[[Minor suggestions]]
The suggestions are structured as shown below.
[Suggested point][Position]
Descriptions.
1. [Abbreviation][Abstract]
The abbreviations (SBS and LCA) should be stated with full names before using them.
2. [Abbreviation][The 2nd paragraph in Introduction]
The abbreviation (GHG) should be stated with the full name before using it.
3. [unit typo][The 4th paragraph in Introduction]
“%wt/wt” in the sentence “Although the reuse of reclaimed asphalt is limited by current technologies to 15-20%wt/wt,…”
4. [More graphene-related materials] [The 5th paragraph in Introduction]
Original text: “Research results have shown that specific NMs, such as graphene nanoplatelets (GNPs) [21], and graphene oxide (GO) [22], can greatly improve the mechanical properties, aging resistance, fatigue resistance, and adhesion properties of asphalt binders. For this reason, it would be desirable to implement a further level of circularity in the roads paving life cycle, also including polymers and NMs.”
In graphene-related materials, graphene nanoribbons (GNRs) possessing "small size effect", "surface and boundary effect", "quantum size effect", and “edge-orientation properties” are suggested to the list of graphene-related materials, enriching the contents for readers [Sci. Technol. Adv. Mater. 11 (2010) 054504, Phys. Chem. Chem. Phys. 18 (2016) 7573].
Author Response
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Reviewer 2 Report
1. This paper assesses the potential environmental comparative impact throughout the life cycle of standard road pavements (with neat bitumen), pavements containing a traditional polymer-based modifier (styrene-butadiene-styrene (SBS), and pavements containing innovative hard plastics and graphene-based modifier using LCA. however, the main question or research motivation is not clear.
2. The topic is relevant, interesting and original because it incorporates new bitumen modifier and related formulation.
3. This study is different from other published studies in terms of study approach and materials. Detailed LCA was carried out to assess the environmental benefits of recycled hard plastic combined with graphene to generate a new bitumen concrete modifier and formulation. The performances of the new modifier were compared based on 3 case studies.
Hence, the new findings from this study contribute to the body of knowledge, particularly on environmental performance.
4. The paper is appropriately written. However, some numbering formats can be changed to avoid confusion.
5. The conclusions are consistent with the research question. Evidence of results and arguments are presented clearly.
6. References are mostly recent five years.
Comments for author File: 
Comments.pdf
Author Response
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Reviewer 3 Report
The aim of the paper is interesting and the use of hard plastic, combined with graphene, is gaining attention in the last years. The manuscript is well written in an understandable manner, and the methods and results are clearly presented. Here some minor comments:
-provide a short description of ECOPAVE project, such as the country where it is develop, also in the introduction (beyond the acknowledgment).
-a deep research was conducted the mechanical performance of HMAs produced with the same recycled plastics and graphene: https://doi.org/10.1617/s11527-022-01954-4 and https://doi.org/10.1016/j.conbuildmat.2022.128725 . Please evaluate if these results can improve the state of art of Your paper.
-conform the way you refer to asphalt concrete, since sometimes is 'asphalt', 'bitumen concrete' (with acronym), 'bituminous conglomerate', 'bituminous mixtures'.
- I may suggest to include a table in section2.1 to summarize the three different scenarios;
-In the text, cite Table 5, then 3 and 4 before Table 1 and 2 is not correct.
-The diagram in Figure 1 is not clear. Moreover, the object of the figure should be described in the text and not in the caption.
In section 2.2.2 and 2.2.3, provide some references for electricity, methane and fuel consumption.
-Table 5, 'wearing' layer.
-The conclusion are too long.
-Did You consider and evaluate the effects of the recycled hard plastic in recycling the pavement (mostly the RAP bitumen) at the end of life?
Author Response
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Reviewer 4 Report
The article is a significant study. Despite the overall positive impression, there are several comments to the presented material:
1. It is necessary to specify the size of the fractions of plastics and modifiers introduced into the asphalt mixture.
2. On page 17 there is an unfinished phrase: "The results reported below are referred to innovative modifier and SBC (figure 5) and"
3. If the authors conducted a study of the durability of the developed asphalt mixtures, it is necessary to refer to the results of this study and indicate that these building materials not only do not have a significant impact on the environment, but also have improved performance characteristics. The study of corrosion resistance and performance characteristics of the developed asphalt mixtures may become a topic for further research.
Author Response
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