Potential Carbon Footprint Reduction for Reclaimed Asphalt Pavement Innovations: LCA Methodology, Best Available Technology, and Near-Future Reduction Potential

Round 1

Reviewer 1 Report

The article was structured very well, and in the abstract and introduction part, the objective was addressed clearly. Documenting the literature on the similar investigations sufficiently provided and discussed. And the novelty of this study was located precisely among the published studies. The applied methodology was formulated clearly and obtained numerical results were well provided using appropriate statistics, tables and figures.
A comprehensive discussion addressing the concluding remarks and further studies having potential for research were provided in the final section.
The submitted paper is well prepared for publication in Journal Sustainability
I suggest to accept.

Author Response

Dear reviewer, 

 

based on the feedback received I understand that the paper is fit to be published as is.

Kind regards.

Reviewer 2 Report

Congratulations to Authors. Very interesting paper regarding the Carbon footprints for three asphalt mixtures (SMA, PA and AC), with different percentages of RAP, using a LCA methodology.

In general, the paper is well presented but some information shall be clarified or completed:

1. It seems appropriate to include a list of acronyms (or “Abbreviations”) before “References”;
2. Under the International System (SI) of Units recommendations (2019), a space must separate the number and the percentage symbol (“## %” and not “##%”);
3. The same recommendation is made for Celsius degree symbol (“## °C” and not “##°C”);
4. The symbol for unit “tonne”, as non-SI unit accepted for use with the SI Units, is “t” and not “ton”;
5. Lines 208/209: “Asphalt materials can be overheated up to 270 °C without causing bitumen aging …”. Are you sure about this non aging?
6. Line 160: please correct “Error! Reference source not found”;
7. Line 169: in fact, “quicklime” is the best filler but, due to safety reasons, the most used has been hydrated lime (in addition to calcium carbonate);
8. Line 270: the Authors informed that “the modelling follows the European standard EN15804 …”. Please be in mind that the new EN 17392-1 provides “additional rules for Environmental Product Declarations (EPD) specifically for bituminous mixtures” and “it complements the core product category rules for all construction products and services as established in EN 15804”;
9. Line 325 (Table 2): it doesn’t seem clear what is the bitumen content (virgin) in each of 9 compositions for these three mixtures (SMA surf, PA surf and AC bin/base);
10. Again, line 325 (Table 2): is the high percentage of RAP content (93 %), included in two types of discontinuous asphalt mixtures (SMA and PA), so common (in pavements at large)?
11. Equation 1: please replace the symbol “∗” by “×”;
12. Lines 353 & 356: please replace “kj/°C/kg” by “kJ/°C/kg”;
13. Line 377 (Equation 3): you don’t need to use the “×” symbol before the independent variable (T);
14. Lines 416/426: please correct the notes numbers (1 to 5 instead of 4 to 8);
15. Section “4.1 Limitations of the study”: differences in RAP content and in total bitumen content induce significant differences in the lifetime of the asphalt layers (made with SMA surf, PA surf or AC bin/base). Please comment better this evidence (in addition to the simple paragraph “… the possible difference in technical performance of asphalt mixtures, the most important of them being service life” – lines 569/570). In my opinion, the assumption that “RAP containing mixtures have the same technical performance and service life as the 100 % primary mixtures”, even supported by “results of test sections from RWS which used WMA Porous Asphalt 93 % RAP”, is an important limitation of this study;
16. Line 579: please define the acronym RWS (runways?);
17. Line 584: please verify if some of the identified uncertainties in the “system boundaries” are reduced by the EN 17392-1;
18. If possible, the Authors may also include some information regarding other important aspect for the application industry: average direct costs for each of the studied solutions;
19. Section “5 Conclusions”: it is fundamental to include a summary information on all limitations of the study referred to in Section 4.1;
20. Line 691 (Funding): “This research received no external funding” but to some extent, overemphasizes the attributes of a commercial product (Sylvaroad). I would recommend greater discretion in some sentences.

Author Response

Dear reviewer,

 

We have addressed all your comments. You can see a point to point response in the attachment.

Kind regards.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

I appreciated the authors' responses and I think the manuscript can be published.

I only request the correction of the word "anan" in line 672.

Regarding editing, the separation between numbers and the respective units should be avoided, as for example in lines 492/493.

Author Response

Dear Reviewer, 

1.

the word "anan" has been corrected as requested and now the sentence in line 672 reads:

"...need further investigation along with an analysis of..."

 

2.

I fixed the problem in lines 492/493 and went through the document and made sure that numbers and units would appear next to each other but I'm afraid this may happen again once the changes in the document are accepted.

 

Kind regards.