Life Cycle Carbon Emissions and an Uncertainty Analysis of Recycled Asphalt Mixtures
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsRE: Life cycle carbon emissions and uncertainty analysis of recycled asphalt mixtures
This manuscript is very well prepared and organized. The writing is innovative and of high quality. I consider this manuscript suitable for acceptance and publication in the journal. However, before being accepted for publication in the journal, a series of revisions are required, which are mentioned below:
1- The manuscript needs to be edited in English.
2- The references should be carefully checked and adjusted according to the journal format.
3- Please revise problems in the figures 5, 6 and 7. Are Ok the titles of the Y axes? I doubt this. also; Pay attention to the written legend in figures 6 and 7. Two of the legends are written in Chinese language, which cannot be understood by international readers. Please check and correct these three figures carefully.
Comments on the Quality of English LanguageRE: Life cycle carbon emissions and uncertainty analysis of recycled asphalt mixtures
This manuscript is very well prepared and organized. The writing is innovative and of high quality. I consider this manuscript suitable for acceptance and publication in the journal. However, before being accepted for publication in the journal, a series of revisions are required, which are mentioned below:
1- The manuscript needs to be edited in English.
2- The references should be carefully checked and adjusted according to the journal format.
3- Please revise problems in the figures 5, 6 and 7. Are Ok the titles of the Y axes? I doubt this. also; Pay attention to the written legend in figures 6 and 7. Two of the legends are written in Chinese language, which cannot be understood by international readers. Please check and correct these three figures carefully.
Author Response
Reviewer 1
RE: Life cycle carbon emissions and uncertainty analysis of recycled asphalt mixtures
This manuscript is very well prepared and organized. The writing is innovative and of high quality. I consider this manuscript suitable for acceptance and publication in the journal. However, before being accepted for publication in the journal, a series of revisions are required, which are mentioned below:
Reply:
Thank you for your recognition of our work.
1- The manuscript needs to be edited in English.
Reply
Thank you for your comment, a professional proofreader has read and revised the text.
2- The references should be carefully checked and adjusted according to the journal format.
Reply
Thank you, the references has been carefully checked and adjusted according to the journal format, please see below.
References
1. China government website, Peak Carbon Action Program by 2030, 2021. https://www.gov.cn/gongbao/content/2021/content_5649731.htm?eqid=e82790c90001dc23000000036459fff2
2. International Green Economy Association. Global Carbon Budget Report 2022, 2022. https://mp.weixin.qq.com/s?__biz=MzUzNzI1NjU4MA==&mid=2247514358&idx=2&sn=b68e29fa54866c5b954ed324c2b0b55a&chksm=faeb4f1dcd9cc60b0acc64ef84b7ad380713a33f3202a4812dcdb89c3a2e8e3d49d409624a37&scene=27.
3. Mejia A. Evaluation of the UNECE ITC support to governments in climate change mitigation: lessons from the use of ForFITS tool that links policy choices and CO2 emission scenarios for inland transport. UNECE, 2019.
4. Ministry of Transport of the People's Republic of China. 2022 Statistical Bulletin on the Development of the Transportation Industry, 2023. https://xxgk.mot.gov.cn/2020/jigou/zhghs/202306/t20230615_3847023.html
5. Santos J, Ferreira A, Flintsch G. A life cycle assessment model for pavement management: methodology and computational framework. Int J Pavement Eng. 2015. 16(3): 268-286.
6. Horvath A, Hendrickson C. Comparison of environmental implications of asphalt and steelreinforced concrete pavements. Transport Res Rec. 1998, 1626(1): 105-113.
7. Santos J, Ferreira A, Flintsch G. A life cycle assessment model for pavement management: methodology and computational framework. Int J Pavement Eng. 2015, 16(3): 268-286.
8. Huang Y, Bird R, Heidrich R O. Development of a life cycle assessment tool for construction and maintenance of asphalt pavements. J Clean Prod. 2009, 17(2): 283-296.
9. Aurangzeb Q, Al-Qadi I L, Ozer H, et al. Hybrid life cycle assessment for asphalt mixtures with high RAP content. Resour Conserv Recy. 2014, 83: 77-8
10. Meng L. Energy consumption and emission assessment of asphalt pavement in Heilongjiang Province based on LCA. Northeast Forestry University,2018.
11. Giani M I, Dotelli G, Brandini N, et al. Comparative life cycle assessment of asphalt pavements using reclaimed asphalt, warm mix technology and cold in-place recycling. Resour Conserv Recy. 2015, 104: 224-238.
12. Santos J, Bryce J, Flintsch G, et al. A life cycle assessment of in-place recycling and conventional pavement construction and maintenance practices. Struct Infrastruct E. 2015, 11(9): 1199-1217.
13. Farina A, aanetti M C, Santagata E, et al. Life cycle assessment applied to bituminous mixtures containing recycled materials: Crumb rubber and reclaimed asphalt pavement. Resour Conserv Recy. 2017, 117: 204-212.
14. Gulotta T M, Mistretta M, Praticò F G. A life cycle scenario analysis of different pavement technologies for urban roads. Sci Total Environ. 2019, 673: 585-593.
15. Devulapalli L, Kothandaraman S, Sarang G. Evaluation of rejuvenator’s effectiveness on the reclaimed asphalt pavement incorporated stone matrix asphalt mixtures. Constr Build Mater, 2019, 224: 909-919.
16. Miliutenko S, Björklund A, Carlsson A. Opportunities for environmentally improved asphalt recycling: the example of Sweden. J Clean Prod. 2013, 43: 156-165.
17. Peng J, Sun N, Ling J, et al. Research on aging characteristics and simulated aging test method of SBS modified asphalt. Highway Engineering.2019,44(01):63-69+119.
18. Aurangzeb Q, Al-Qadi I L. Asphalt pavements with high reclaimed asphalt pavement content: economic and environmental perspectives. Transport Res Rec. 2014, 2456(1):
19. Siverio Lima M S, Hajibabaei M, Hesarkazzazi S, et al. Environmental Potentials of Asphalt Materials Applied to Urban Roads: Case Study of the City of Münster. Sustainability, 2020, 12(15), 6113.
20. Santos J, Bryce J, Flintsch G, et al. A life cycle assessment of in-place recycling and conventional pavement construction and maintenance practices. Struct Infrastruct E. 2015, 11(9): 1199-1217.
21. Aurangzeb Q, Al-Qadi I L. Asphalt pavements with high reclaimed asphalt pavement content: economic and environmental perspectives. Transport Res Rec. 2014, 2456(1): 161-169.
22. Santos J, Bressi S, Cerezo V, et al. Life cycle assessment of low temperature asphalt mixtures for road pavement surfaces: A comparative analysis. Resour Conserv Recy. 2018, 138: 283-297.
23. Puccini M, Leandri P, Tasca A L, et al. Improving the Environmental Sustainability of Low Noise Pavements: Comparative Life Cycle Assessment of Reclaimed Asphalt and Crumb Rubber Based Warm Mix Technologies. Coatings. 2019, 9(5): 343.
24. Aurangzeb Q, Al-Qadi I L, Ozer H, et al. Hybrid life cycle assessment for asphalt mixtures with high RAP content. Resour Conserv Recy. 2014, 83: 77-86.
25. Santos J, Bryce J, Flintsch G, et al. A life cycle assessment of in-place recycling and conventional pavement construction and maintenance practices. Struct Infrastruct E. 2015, 11(9): 1199-1217.
26. Santos J, Flintsch G, Ferreira A. Environmental and economic assessment of pavement construction and management practices for enhancing pavement sustainability. Resour Conserv Recy. 2017, 116: 15-31.
27. Li W E, Peng B, Lv WQ. Research on energy saving and emission reduction technology of asphalt mixture. Transp Ene Sav Environ Prot. 2014,10(03):68-71.
28. Liu L. Research on energy saving and carbon reduction benefits of recycled asphalt mixtures. Highway Eng. 2014,39(04):10-16.
29. Lei B, Zhou J, Yu L, et al. Evaluation of environmental benefits of recycled asphalt mixtures prepared from waste materials over the whole life cycle. New Build Mater.2023,50(05):56-60.
30. Li W. Environmental protection and carbon reduction benefits of recycled asphalt mixture technology. Fujian Transp Sci Technol. 2020, 176(05):43-47.
31. Yang W, Cai H. Research on carbon emission calculation model of asphalt mixture construction process. Highway Motor Transp. 2018, 184(01):183-186.
32. Ma J. Analysis of CO2 emission and its uncertainty in the building construction stage. J Civ Environ Ene. 2022,44(06):209-218.
33. Zhang T, Gao Y, He X, et al. Research on energy saving and emission reduction effect of warm mix recycled asphalt pavement during construction period based on LCA. Highway.2019,64(04):287-293.
3- Please revise problems in the figures 5, 6 and 7. Are Ok the titles of the Y axes? I doubt this. also; Pay attention to the written legend in figures 6 and 7. Two of the legends are written in Chinese language, which cannot be understood by international readers. Please check and correct these three figures carefully.
Reply
Thank you for your comment. We have modified figures 5, 6 and 7, please see below.
Figure 5. CO2 emissions for different production methods.
Figure 6. CO2 emissions from different material losses.
Figure 7. CO2 emissions associated with the use of different materials during the transportation phase.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsReview report. Minor corrections
The paper "Life cycle carbon emissions and uncertainty analysis of recycled asphalt mixtures" explains the efficient recycling of road materials as an effective way to reduce carbon emissions. A whole life cycle CO2 emission calculation model for recycled asphalt mixtures is established, and uncertainty analysis is carried out on the basis of this model. The steps in the recycled asphalt mixture stage with the greatest impact on emissions are identified. The life cycle of asphalt mixtures is divided into raw material production, mixture preparation, material transportation and construction and building phases based on the carbon emissions trends in the four phases.
Comments on the overall concept: The paper is interesting, and the findings will be useful in real-world situations. The topic is comparatively novel in terms of science. According to my anti-plagiarism engine, this collection of authors' works is not comparable to any other works. References used are acceptable. The explanation of the LCA analysis is sufficiently introduced. Results and analyses are adequate. The figures are good, save for the few mistakes which will be explained in Specific comments. The conclusion is following the presented results. The references are UpToDate (from the past 5 years or so). Used literature are pertinent. There are not too many self-citations.
Specific comments:
1. The abstract is informative. It can be slightly abridged and shortened. Also authors should mention what gap in knowledge their work is closing.
2. Keywords are informative.
3. A well-written introduction and a review of the literature. The text is straightforward and easy to read. A comprehensive overview of the literature is provided. The literature review is thorough, well-written, and relevant to the study topic. Nonetheless, the authors should highlight the paper's virtues and what exactly is new and distinct on global level.
4. The quality and presentation in Fig.4 can be improved.
5. Table 7 should be reformatted for the text to fit in the proposed page dimensions.
6. Figures 6 and 7 – there is text in Chinese in the legend which should be translated in English.
7. English language is readable. A native English speaker or a professional proofreader should read and revise the text.
11. The listed references are relevant and current (within the last 5 years or so). The used literature is appropriate. There are no excessive self-citations.
Comments on the Quality of English Language
English language is readable. A native English speaker or a professional proofreader should read and revise the text.
Author Response
Reviewer 2 Review report. Minor corrections The paper "Life cycle carbon emissions and uncertainty analysis of recycled asphalt mixtures" explains the efficient recycling of road materials as an effective way to reduce carbon emissions. A whole life cycle CO2 emission calculation model for recycled asphalt mixtures is established, and uncertainty analysis is carried out on the basis of this model. The steps in the recycled asphalt mixture stage with the greatest impact on emissions are identified. The life cycle of asphalt mixtures is divided into raw material production, mixture preparation, material transportation and construction and building phases based on the carbon emissions trends in the four phases. Comments on the overall concept: The paper is interesting, and the findings will be useful in real-world situations. The topic is comparatively novel in terms of science. According to my anti-plagiarism engine, this collection of authors' works is not comparable to any other works. References used are acceptable. The explanation of the LCA analysis is sufficiently introduced. Results and analyses are adequate. The figures are good, save for the few mistakes which will be explained in Specific comments. The conclusion is following the presented results. The references are UpToDate (from the past 5 years or so). Used literature are pertinent. There are not too many self-citations. Reply Thank you for your recognition of our work. Specific comments: 1. The abstract is informative. It can be slightly abridged and shortened. Also authors should mention what gap in knowledge their work is closing. Reply In the revised manuscript, we have abridged and shortened the abstract and research gap is also added, please see below. Abstract: The efficient recycling of road materials is an effective way to reduce carbon emissions. Approximately 400 million tons of waste asphalt pavement materials are generated annually in China, but the utilization rate is less than 50%. In this paper, a whole life cycle CO2 emission calculation model for recycled asphalt mixtures is established, and uncertainty analysis is carried out on the basis of this model. The steps in the recycled asphalt mixture stage with the greatest impact on emissions are identified. The life cycle of asphalt mixtures is divided into raw material production, mixture preparation, material transportation and construction phases based on the carbon emissions trends in the four phases. First, recycled asphalt mixtures are considered, and the carbon emissions along a two-way four-lane highway are analyzed based on the relevant carbon emission factor and other known data. The carbon dioxide emissions of each stage are also compared to identify the key links among stages. Then, the carbon emissions of hot recycled asphalt mixtures are compared with those of ordinary asphalt mixtures and cold recycled asphalt mixtures in each stage. Finally, an analytical uncertainty study of recycled asphalt mixtures is conducted using uncertainty modeling in different scenarios. Based on the quantitative results of the carbon emission calculations through life cycle assessment (LCA), future measures for reducing carbon emissions from recycled asphalt mixtures are proposed. 2. Keywords are informative. Reply Thank you for your comment. The Keywords has been modified as follows. Keywords: Recycled asphalt mixtures; Life cycle carbon emissions; Different stages; Uncertainty Analysis 3. A well-written introduction and a review of the literature. The text is straightforward and easy to read. A comprehensive overview of the literature is provided. The literature review is thorough, well-written, and relevant to the study topic. Nonetheless, the authors should highlight the paper's virtues and what exactly is new and distinct on global level. Reply Thank you for your comment. The paper's virtues and what exactly is new and distinct on global level is highlighted, please see below. Most studies have focused on a single life cycle stage, and there have been few studies on the LCA of recycled asphalt mixtures over the complete life cycle. Moreover, assessments of the results of LCA research, uncertainty analyses and other methods need to be enriched and supplemented. Considering different asphalt production stages, different steps in these stages, and different reasons for the emission of carbon dioxide due to various factors, the effects of various factors on carbon emissions are analyzed to quantify carbon emissions and identify key links to develop targeted energy-saving and emission reduction measures. 4. The quality and presentation in Fig.4 can be improved. Reply In the revised manuscript, Fig.4 has been modified, please see below. (a) Raw material production stage (b) Mix preparation stage (c) Transportation stage (d) Emissions from recycled asphalt mixtures by stages Figure 4. Comparison of carbon emissions in different stages. 5. Table 7 should be reformatted for the text to fit in the proposed page dimensions. Reply We have reformatted Table 7 to fit in the proposed page dimensions, please see below. Table 7. Uncertainty quantification results for mineral powder. DQI scoreUncertaintyTotal Type of uncertainty Mineral powder uncertainty Source reliability 2 0.025 U_i=0.0371 Sample integrity30.025 Technical representativeness20.01 Temporal representativeness10 Geographic representativeness20.005 Fundamental uncertainty U_b=0.0006 U_(d,i)=0.0371 Type of uncertainty Modified asphalt uncertainty Source reliability20.025 Sample integrity20.01 Technical representativeness 2 0.01 U_i=0.0292 Temporal representativeness10 Geographic representativeness20.005 Fundamental uncertainty U_b=0.0006 U_(d,i)=0.0292 6. Figures 6 and 7 – there is text in Chinese in the legend which should be translated in English. Reply In the revised manuscript, Figures 6 and 7 has been modified, please see below. Figure 6. CO2 emissions from different material losses. Figure 7. CO2 emissions associated with the use of different materials during the transportation phase. 7. English language is readable. A native English speaker or a professional proofreader should read and revise the text. Reply Thank you for your comment, a professional proofreader has read and revised the text. 8. The listed references are relevant and current (within the last 5 years or so). The used literature is appropriate. There are no excessive self-citations. Reply Thank you for your comment. The references have been modified as follows. References China government website, Peak Carbon Action Program by 2030, 2021. https://www.gov.cn/gongbao/content/2021/content_5649731.htm?eqid=e82790c90001dc23000000036459fff2 International Green Economy Association. Global Carbon Budget Report 2022, 2022. https://mp.weixin.qq.com/s?__biz=MzUzNzI1NjU4MA==&mid=2247514358&idx=2&sn=b68e29fa54866c5b954ed324c2b0b55a&chksm=faeb4f1dcd9cc60b0acc64ef84b7ad380713a33f3202a4812dcdb89c3a2e8e3d49d409624a37&scene=27. Mejia A. Evaluation of the UNECE ITC support to governments in climate change mitigation: lessons from the use of ForFITS tool that links policy choices and CO2 emission scenarios for inland transport. UNECE, 2019. Ministry of Transport of the People's Republic of China. 2022 Statistical Bulletin on the Development of the Transportation Industry, 2023. https://xxgk.mot.gov.cn/2020/jigou/zhghs/202306/t20230615_3847023.html Santos J, Ferreira A, Flintsch G. A life cycle assessment model for pavement management: methodology and computational framework. Int J Pavement Eng. 2015. 16(3): 268-286. Horvath A, Hendrickson C. Comparison of environmental implications of asphalt and steelreinforced concrete pavements. Transport Res Rec. 1998, 1626(1): 105-113. Santos J, Ferreira A, Flintsch G. A life cycle assessment model for pavement management: methodology and computational framework. Int J Pavement Eng. 2015, 16(3): 268-286. Huang Y, Bird R, Heidrich R O. Development of a life cycle assessment tool for construction and maintenance of asphalt pavements. J Clean Prod. 2009, 17(2): 283-296. Aurangzeb Q, Al-Qadi I L, Ozer H, et al. Hybrid life cycle assessment for asphalt mixtures with high RAP content. Resour Conserv Recy. 2014, 83: 77-8 Meng L. Energy consumption and emission assessment of asphalt pavement in Heilongjiang Province based on LCA. Northeast Forestry University,2018. Giani M I, Dotelli G, Brandini N, et al. Comparative life cycle assessment of asphalt pavements using reclaimed asphalt, warm mix technology and cold in-place recycling. Resour Conserv Recy. 2015, 104: 224-238. Santos J, Bryce J, Flintsch G, et al. A life cycle assessment of in-place recycling and conventional pavement construction and maintenance practices. Struct Infrastruct E. 2015, 11(9): 1199-1217. Farina A, aanetti M C, Santagata E, et al. Life cycle assessment applied to bituminous mixtures containing recycled materials: Crumb rubber and reclaimed asphalt pavement. Resour Conserv Recy. 2017, 117: 204-212. Gulotta T M, Mistretta M, Praticò F G. A life cycle scenario analysis of different pavement technologies for urban roads. Sci Total Environ. 2019, 673: 585-593. Devulapalli L, Kothandaraman S, Sarang G. Evaluation of rejuvenator’s effectiveness on the reclaimed asphalt pavement incorporated stone matrix asphalt mixtures. Constr Build Mater, 2019, 224: 909-919. Miliutenko S, Björklund A, Carlsson A. Opportunities for environmentally improved asphalt recycling: the example of Sweden. J Clean Prod. 2013, 43: 156-165. Peng J, Sun N, Ling J, et al. Research on aging characteristics and simulated aging test method of SBS modified asphalt. Highway Engineering.2019,44(01):63-69+119. Aurangzeb Q, Al-Qadi I L. Asphalt pavements with high reclaimed asphalt pavement content: economic and environmental perspectives. Transport Res Rec. 2014, 2456(1): Siverio Lima M S, Hajibabaei M, Hesarkazzazi S, et al. Environmental Potentials of Asphalt Materials Applied to Urban Roads: Case Study of the City of Münster. Sustainability, 2020, 12(15), 6113. Santos J, Bryce J, Flintsch G, et al. A life cycle assessment of in-place recycling and conventional pavement construction and maintenance practices. Struct Infrastruct E. 2015, 11(9): 1199-1217. Aurangzeb Q, Al-Qadi I L. Asphalt pavements with high reclaimed asphalt pavement content: economic and environmental perspectives. Transport Res Rec. 2014, 2456(1): 161-169. Santos J, Bressi S, Cerezo V, et al. Life cycle assessment of low temperature asphalt mixtures for road pavement surfaces: A comparative analysis. Resour Conserv Recy. 2018, 138: 283-297. Puccini M, Leandri P, Tasca A L, et al. Improving the Environmental Sustainability of Low Noise Pavements: Comparative Life Cycle Assessment of Reclaimed Asphalt and Crumb Rubber Based Warm Mix Technologies. Coatings. 2019, 9(5): 343. Aurangzeb Q, Al-Qadi I L, Ozer H, et al. Hybrid life cycle assessment for asphalt mixtures with high RAP content. Resour Conserv Recy. 2014, 83: 77-86. Santos J, Bryce J, Flintsch G, et al. A life cycle assessment of in-place recycling and conventional pavement construction and maintenance practices. Struct Infrastruct E. 2015, 11(9): 1199-1217. Santos J, Flintsch G, Ferreira A. Environmental and economic assessment of pavement construction and management practices for enhancing pavement sustainability. Resour Conserv Recy. 2017, 116: 15-31. Li W E, Peng B, Lv WQ. Research on energy saving and emission reduction technology of asphalt mixture. Transp Ene Sav Environ Prot. 2014,10(03):68-71. Liu L. Research on energy saving and carbon reduction benefits of recycled asphalt mixtures. Highway Eng. 2014,39(04):10-16. Lei B, Zhou J, Yu L, et al. Evaluation of environmental benefits of recycled asphalt mixtures prepared from waste materials over the whole life cycle. New Build Mater.2023,50(05):56-60. Li W. Environmental protection and carbon reduction benefits of recycled asphalt mixture technology. Fujian Transp Sci Technol. 2020, 176(05):43-47. Yang W, Cai H. Research on carbon emission calculation model of asphalt mixture construction process. Highway Motor Transp. 2018, 184(01):183-186. Ma J. Analysis of CO2 emission and its uncertainty in the building construction stage. J Civ Environ Ene. 2022,44(06):209-218. Zhang T, Gao Y, He X, et al. Research on energy saving and emission reduction effect of warm mix recycled asphalt pavement during construction period based on LCA. Highway.2019,64(04):287-293.Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsAn interesting article on an important topic related to the assessment of life cycle carbon emissions. The manuscript addresses the carbon footprint of China, which is one of the greenhouse gas emitters, which is of course not surprising given the size of the country.
The aricle does not present a novel approach to the problem and does not have a significant impact on the state of knowledge. However, it is relevant for engineering and environmental reasons.
The following are comments that should improve the manuscript:
"2.1. Research on carbon emissions of ordinary asphalt mixtures" the chapter should be expanded to include the state of the art
abbreviations used for the first time should be clarified
Table 4. the accuracy of the results should be the same for "material mass"
Fugire 4 Give the value as a percentage with pie charts, work on the visual aspect of these charts
Figure 5 y-axis "Carbon dioxide emission" consider how to better describe the values
Figure 6 Use the Latin alphabet in the legend, similar to Figure 5, consider how to better describe the y-axis
Figure 7 in the legend use the Latin alphabet similarly to Figure 5 consider how to better describe the y-axis
In the text you use e.g. 3.1 E +05 kg maybe you should use Mg then it would be 310 Mg
Regards to the authors
Author Response
Reviewer 3 An interesting article on an important topic related to the assessment of life cycle carbon emissions. The manuscript addresses the carbon footprint of China, which is one of the greenhouse gas emitters, which is of course not surprising given the size of the country. The aricle does not present a novel approach to the problem and does not have a significant impact on the state of knowledge. However, it is relevant for engineering and environmental reasons. The following are comments that should improve the manuscript: 1. "2.1. Research on carbon emissions of ordinary asphalt mixtures" the chapter should be expanded to include the state of the art abbreviations used for the first time should be clarified Reply Thank you, we have modified this in the revised manuscript. Most of the early Life Cycle Assessment (LCA) studies of pavement focused on comparisons regarding concrete pavements and asphalt pavements [5]. Horvath et al. published the earliest LCA pavement study in 1998 in which Continuously Reinforced Concrete Pavements (CRCP) and hot-mixed asphalt (HMA) pavements were compared; the results indicated the disadvantage of asphalt pavements in terms of the high consumption of raw materials, but on most of the environmental impact indicators, concrete pavements have a higher environmental impact than asphalt pavements. Moreover, end-of-life (EOL) recycling studies of both materials have shown the green sustainability associated with the effective recycling of asphalt pavements, and on the contrary, the recycling of CRCP may result in a greater environmental burden [6]. Santos et al. developed an LCA model for pavement management to assess the effects of flexible pavement structures during their life cycle, as defined in the Portuguese Pavement Design Handbook (PPDH). The study concluded that the material and use phases have the highest environmental impacts throughout the life cycle [7]. 2. Table 4. the accuracy of the results should be the same for "material mass" Reply The accuracy of the results has been modified to keep the same for "material mass" in Table 4. Please see below. Table 4. Energy consumption of equipment for producing different recycled asphalt mixtures. Structural layer Engineering quantity (m3) Material mass (t) Electricity and fuel consumption by equipment Diesel fuel (kg)Heavy oil (kg)Electricity (kwh) Upper layer SMA-13 600 1470.00 290.28 11725.96 4417.03 Mid-surface layer AC-20 900 2169.00 435.42 14983.17 5643.96 Lower layer AC-25 (Recycled) 2250 5314.02 1049.36 35806.83 13488.18 AC-25 (Ordinary)22505334.421045.3435669.8913436.60 HiRM22505271.32412.1100 3. Fugire 4 Give the value as a percentage with pie charts, work on the visual aspect of these charts Reply In the revised manuscript, Fig.4 has been modified, please see below. (a) Raw material production stage (b) Mix preparation stage (c) Transportation stage (d) Emissions from recycled asphalt mixtures by stages Figure 4. Comparison of carbon emissions in different stages. 4. Figure 5 y-axis "Carbon dioxide emission" consider how to better describe the values Reply In the revised manuscript, Fig.5 has been modified, please see below. Figure 5. CO2 emissions for different production methods. 5. Figure 6 Use the Latin alphabet in the legend, similar to Figure 5, consider how to better describe the y-axis Reply In the revised manuscript, Fig.6 has been modified, please see below. Figure 6. CO2 emissions from different material losses. 6. Figure 7 in the legend use the Latin alphabet similarly to Figure 5 consider how to better describe the y-axis Reply In the revised manuscript, Fig.7 has been modified, please see below. Figure 7. CO2 emissions associated with the use of different materials during the transportation phase. 7. In the text you use e.g. 3.1 E +05 kg maybe you should use Mg then it would be 310 Mg Reply Thank you. We have modified this as follows. An adjustment to the RAP proportion also has the greatest effect on reducing CO2 emissions, a change of 310 Mg of CO2 eq. When thermal power generation is replaced by hydroelectric power generation, the carbon emission reduction achieved by adjusting the RAP proportion is the largest, and CO2 emissions are reduced by 32%, or 131 Mg of CO2 eq.Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for AuthorsPlease read the attached paper with my comments in that. Some editing is required before complete acceptance
The paper is generally good but it needs some editing like:
1- the mix designs are not clear so the calculations are not clearly follow able
2- the thickness of the base layer in all three cases is the same which definitely leads to different service life’s which is not considered
3- in my opinion no model is established but three cases were compared and it is important to mention that this is kind of cradle to gate as the service phase and the possible maintenance options are not considered
4- sensitivity analysis could be better to be performed on different RAP contents too
5- the cold recycled mixes normally contain higher than 20% RAP and also with a small amount of cement (1%). It is important to mention the mix design of the mixes which were considered in the study
Comments for author File: Comments.pdf
I did some small corrections. The most important point is that there are some words which are not common in this field, please try to replace them. Generally please don’t use long sentences with a lot of comma and “and”. Sometimes it is not easy to follow up the main point of the sentence.
Author Response
Reviewer 4
Please read the attached paper with my comments in that. Some editing is required before complete acceptance
The paper is generally good but it needs some editing like:
1- the mix designs are not clear so the calculations are not clearly follow able
Reply
Table 5 shows the mix designs of different asphalt mixtures, please see below.
Table 5. Calculation of carbon emissions during the transportation phase of thermally recycled materials.
|
|
Transportation materials |
Modified asphalt |
Aggregate |
Talcum powder |
RAP |
Emulsified asphalt |
Mixed material |
|
Hot-recycled asphalt |
Mass (t) |
423.93 |
7284.8 |
207.75 |
1063.52 |
/ |
8953.02 |
|
Load capacity (t) |
20 |
20 |
20 |
20 |
/ |
20 |
|
|
One-way distance (km) |
10 |
10 |
10 |
10 |
/ |
35 |
|
|
Fuel consumption (kg) |
289.89 |
4981.61 |
142.07 |
727.27 |
/ |
17781.61 |
|
|
Ordinary asphalt |
Mass (t) |
473.67 |
8090.56 |
409.17 |
/ |
/ |
8973.4 |
|
Load capacity (t) |
20 |
20 |
20 |
/ |
/ |
20 |
|
|
One-way distance (km) |
10 |
10 |
10 |
/ |
/ |
35 |
|
|
Fuel consumption (kg) |
323.89 |
5531.55 |
279.80 |
/ |
/ |
17822.08 |
|
|
Cold-recycled asphalt |
Mass (t) |
140.19 |
7286.2 |
166.21 |
1063.52 |
178.99 |
8835.11 |
|
Load capacity (t) |
20 |
20 |
20 |
20 |
20 |
100 |
|
|
One-way distance (km) |
10 |
10 |
10 |
10 |
10 |
50 |
|
|
Fuel consumption (kg) |
95.86 |
4981.61 |
113.66 |
727.27 |
122.39 |
6040.79 |
2- the thickness of the base layer in all three cases is the same which definitely leads to different service life’s which is not considered
Reply
Thank you for your comments, the thickness of the base layer in all three cases is the same which definitely leads to different service life and this will lead to different carbon emissions per year.
As descripted in Section 3.1, the function unit in this paper is defined based on the production of hot-mix recycled asphalt pavement to pave a two-way four-lane highway and the basic parameters are shown in Table 1. The service life of the road is very important, in the future work, we will consider that.
3- in my opinion no model is established but three cases were compared and it is important to mention that this is kind of cradle to gate as the service phase and the possible maintenance options are not considered.
Reply
Thank you for your comment, life cycle assessment includes several stages, from cradle-to-gate, from gate-to-gate, from cradle-to-grave, from cradle-to-cradle. In this manuscript, life cycle of asphalt mixtures is divided into raw material production, mixture preparation, material transportation and construction phase. The research object of paper is asphalt mixtures rather than asphalt pavement, thus we didn’t consider the service phase and the possible maintenance options.
4- sensitivity analysis could be better to be performed on different RAP contents too
Reply
Thank you for your comment, sensitivity analysis is very important in the life cycle assessment of asphalt mixtures and we will consider that in the future work.
5- the cold recycled mixes normally contain higher than 20% RAP and also with a small amount of cement (1%). It is important to mention the mix design of the mixes which were considered in the study
Reply
Thank you for your comment, Table 5 shows the mix designs of different asphalt mixtures, please the reply in Question 1.
- I did some small corrections. The most important point is that there are some words which are not common in this field, please try to replace them. Generally please don’t use long sentences with a lot of comma and “and”. Sometimes it is not easy to follow up the main point of the sentence.
Reply
Thank you for your comment, a professional proofreader has read and revised the text.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Comments and Suggestions for AuthorsIn the graphs, I also suggest changing the unit to Mg instead of kg
Regards
