Rheological and Thermo-Oxidative Aging Properties of Asphalt Modified with a Combination of Sasobit and Linear Low-Density Polyethylene
Round 1
Reviewer 1 Report
1. Avoid use abbreviation in the title
2. LDPE, is Low Density Polyethylene, what do you means by “LLDPE”? Do you mean “Linear Low-density polyethylene”, Please include the right meaning in the research
3. The abstract is too long, it is suggested to be shortened (250 words)
4. (RTFOT) means: rolling thin film oven test, please revise the sentence (line 22)
5. Please arrange the references to be as the journal requirements, you don’t have to make the reference in this form “[11], [13], [14]”
6. Several grammatical errors were observed in the article, please rectify the mistakes
7. The novelty of the research is not clear and should be described
8. Section 2.2. Preparation of the modified asphalt binder should be supported by references
9. The figures (in general) need to improved (please use high-resolution figures)
10. Error bars should be included
11. Please revise Figure 3
12. Flowchart should be added
13. The tests are not sufficient, please add other results such as DSR and BBR
14. The conclusion should be improved
Comments for author File: 
Comments.pdf
Author Response
Comments from Reviewer 1:
Comment 1: Avoid use abbreviation in the title
Response: Thank you for pointing this out. We agree with this and have updated the title.
Comment 2: LDPE, is Low Density Polyethylene, what do you means by “LLDPE”? Do you mean “Linear Low-density polyethylene”, Please include the right meaning in the research
Response: Agree. LLDPE stands for linear low-density polyethylene. The explanation and differentiation from LDPE is presented in Line 48-49.
Comment 3: The abstract is too long; it is suggested to be shortened (250 words)
Response: Thank you for pointing this out. We agree with this and the abstract has been shortened.
Comment 4: (RTFOT) means: rolling thin film oven test, please revise the sentence (line 22)
Response: Agree. We have changed accordingly the meaning of RTFOT. See line 24 on page 1 from the revised draft of the manuscript.
Comment 5: Please arrange the references to be as the journal requirements, you don’t have to make the reference in this form “[11], [13], [14]”
Response: Thank you for pointing this out. We agree and have updated the format.
Comment 6: Several grammatical errors were observed in the article, please rectify the mistakes
Response: Thank you for pointing this out. Grammatical errors have been revised.
Comment 7: The novelty of the research is not clear and should be described
Response: Thank you for pointing this out. Lines 94 to 100 in the revised manuscript address the main objective and the novelty of the research. “The main objective of this paper is to study the effect of Sasobit as an WMA additive for asphalt mixtures. Even though many researchers had used PE based polymers and Sasobit separately to improve asphalt proprieties, very few researchers were reported about the combined effect of PE based polymer and Sasobit on asphalt binder proprieties. The use of Sasobit was consider in order to reduce the high viscous trend of LLDPE-asphalt binders and improve these binders’ workability during mix and compaction stages.”
Comment 8: Section 2.2. Preparation of the modified asphalt binder should be supported by references.
Response: Agree. The relevant references for the experimental design were presented in the line 114-115.
Comment 9: The figures (in general) need to improved (please use high-resolution figures)
Response: We agree. Previous figures have been replaced by improved ones.
Comment 10: Error bars should be included
Response: Thank you for this suggestion. It would have been interesting to have considered this aspect for all experimental data. However, due to high cost for tests, only penetration and softening were run with replicates.
Comment 11: Please revise Figure 3
Response: Agree. We have, accordingly, revised Figure 4 (new number of Figure 3) as it can be seen in the revised manuscript.
Comment 12: Flowchart should be added
Response: Agree. We have incorporated the flowchart to the manuscript.
Comment 13: The tests are not sufficient, please add other results such as DSR and BBR
Response: You have raised an important point, but we don’t agree completely. It’s true that testslike DSR, BBR, SEM, XRD, FTIR, and others has you pointed, would give additional information but they wouldn’t invalidate the actual findings.
Comment 14: The conclusion should be improved
Response: Thank you for pointing this out. The conclusion was thoroughly modified.
Reviewer 2 Report
Tembe et al. have presented the manuscript titled: Rheological and thermo-oxidative aging properties of asphalt modified with a combination of Sasobit and LLDPE. Overall presentation of the article is good. I have few suggestions for the authors about this article.
1. Authors have to make the abstract more appealing; I think authors have not added the sentence to describe the novelty of this work to catch the readers. Moreover there should be the description of their results (values) as well rather proving the general discussion.
2. I believe the authors have successfully fabricated the pure asphalt and LLDPE-modified binder, but it required the confirmation i.e., XRD analysis or the SEM images with EDS etc. Please add some images of fabricated samples.
3. During the measurement of viscosity have the authors also focused the porosity of the materials?
4. Line 189-190, Authors state “The effect of adding Sasobit into the LLDPE modified asphalt matrix resulted in the decrease of the penetration and ductility and an increase in softening point with the increasing Sasobit content.” Is there any reference for this claim? For such claim the presence of SEM images with porosity results are important.
5. For such materials the stability test depending on ageing time are also important, please comment
Overall good explanation but this study can be made wider with some other calculations to support the claim.
Author Response
Comment 1: Authors have to make the abstract more appealing; I think authors have not added the sentence to describe the novelty of this work to catch the readers. Moreover, there should be the description of their results (values) as well rather proving the general discussion.
Response: Thank you for pointing this out. We agree with this and now the abstract was improved accordingly in the revised version.
Comment 2: I believe the authors have successfully fabricated the pure asphalt and LLDPE-modified binder, but it required the confirmation i.e., XRD analysis or the SEM images with EDS etc. Please add some images of fabricated samples.
Response: Thank you for this suggestion. It would have been interesting to explore this aspect. It’s true that tests like SEM (microstructure), XRD (crystallinity), FTIR (chemical composition) would give additional information, but they wouldn’t invalidate the actual findings.
Comment 3: During the measurement of viscosity have the authors also focused the porosity of the materials?
Response: No, we didn’t look at the porosity. We didn’t consider it as a crucial parameter since the ternary blends shall later undergo mixing with inert to form porous material, before application.
Comment 4: Line 189-190, Authors state “The effect of adding Sasobit into the LLDPE modified asphalt matrix resulted in the decrease of the penetration and ductility and an increase in softening point with the increasing Sasobit content.” Is there any reference for this claim? For such claim the presence of SEM images with porosity results are important.
Response: Thank you for this suggestion. The claim for this result is based on the conventional tests that was performed. In the literature it’s also well documented that, separately, LLDPE and Sasobit reduce the penetration and ductility and increase softening point. So, it was expected that the combinations of both additives would maintain the same tendency.
Comment 4: For such materials the stability test depending on ageing time are also important, please comment
Response: Ageing is primarily associated with the loss of volatile components and oxidation of the bitumen during asphalt mixture construction (short-term ageing) and progressive oxidation during service life in the field (long-term ageing). Asphalt light components slowly oxidizes when in contact with air (oxygen) increasing the viscosity and making the asphalt harder and less flexible. The degree of viscosity is highly dependent on the temperature, time, and the asphalt film thickness. Some authors have stated that prolonged short-term aging, up to 8 h, causes the Marshall stability, indirect tensile strength, and resilient modulus to be increased. Furthermore, it also decreased the permanent deformation.
Reviewer 3 Report
please specify why the Sasobit and LLDPE were selected for the research.
The combination of Saosbit and LLDPE has a negative effect on the ductility of the modified asphalt, which would limit its application. Besides, the asphalt binder modified with LLDPE-Sasobit exhibited higher viscosity, and the asphalt binder modified with only Sasobit displayed overall better performances. I don't understand why those two additives were compounded for the study. The authors must address the application scenarios for your research.
Two commonly used additives (Saosbit and LLDPE) were selected as modifiers for asphalt binder in the study, the effectiveness was evaluated through a series of experiments, but the interactive relationship and compatibility between those two additives were not explored, and thus the value and significance of research were affected.
The conclusions could not just present testing results, more refined and valuable findings or suggestions need to be addressed in them.
Author Response
Comment 1: please specify why the Sasobit and LLDPE were selected for the research.
Response: Thank you for pointing this out. The reason why Sasobit and LLDPE were chosen for this research was incorporated in the manuscripts, lines 60-63; 82-84 and 94 to 100.
Comment 2: The combination of Sasobit and LLDPE has a negative effect on the ductility of the modified asphalt, which would limit its application. Besides, the asphalt binder modified with LLDPE-Sasobit exhibited higher viscosity, and the asphalt binder modified with only Sasobit displayed overall better performances. I don't understand why those two additives were compounded for the study. The authors must address the application scenarios for your research.
Response: The broader scope of the research was to understand the performance of PE base polymers in the asphalt to then use waste polymers. This option might increase the recycling rates of the polymers while combining with improvements in road quality. The initial tests on polymer modified asphalt showed high increase in viscosity, at higher temperatures, and it was necessary to consider a 3rd component in the mixture to control or reduce the viscosity. Therefore, Sasobit was chosen since it has positive impact on reducing asphalt viscosity at high temperatures and is crystalline at room temperature.
The results are promising! The addition of Sasobit into asphalt already modified with LLDPE reduced the viscosity of the binders. This allows them to be used for paving without major changes in the current technology used for blending and compaction of asphalt mixtures.
Comment 3: Two commonly used additives (Sasobit and LLDPE) were selected as modifiers for asphalt binder in the study, the effectiveness was evaluated through a series of experiments, but the interactive relationship and compatibility between those two additives were not explored, and thus the value and significance of research were affected.
Response: Thank you for raising this important point. We only considered the binary blends between asphalt and Sasobit as well as asphalt and LLDPE and later their conjugated ternary blend. Nevertheless, some authors have suggested that the thermal stability is an important parameter to understand the compatibility of blends. Thus, based on that, it cand be drawn that Sasobit-LLDPE are compatible. On the other hand, their chemical structure and composition also suggests high compatibility between these 2 polyolefins.
Comment 4: The conclusions could not just present testing results, more refined and valuable findings or suggestions need to be addressed in them.
Response: Thank you. We agree with this and now the conclusions were significantly improved.
Round 2
Reviewer 1 Report
Good shape after revision
Author Response
We thank you very much for the support in the process. Your positive review has helped us to step up and improve the manuscript.
Reviewer 2 Report
Thank you for providing the detailed response of all issues I raised.
1. For the review of the article, it is important to be sure about the successful fabrication of the materials. XRD and SEM, EDS provide the detail for such purpose. So at least one of which is necessary to be sure about fabrication reported.
2. Porosity test is requested because the materials Sasobit into the LLDPE modified asphalt matrix are renowned to possess low porosity to demonstrate best charaterization. Without the presence of porosity or density analysis how can anyone be sure to achieve such results.
So in my suggestion no doubt authors have addressed some issues but should understand the fact and quality of the journal.
Regards
Author Response
- For the review of the article, it is important to be sure about the successful fabrication of the materials. XRD and SEM, EDS provide the detail for such purpose. So at least one of which is necessary to be sure about fabrication reported.
- We agree that additional tests would have given more insights, especially into the microstructure of these materials. These materials are ternary blends of asphalt, polymer and Sasobit were we show that a better performance of a binder can be achieved by considering the complementary effect of 2 additives (polymer and Sasobit) with distinct thermal behaviour.
- Porosity test is requested because the materials Sasobit into the LLDPE modified asphalt matrix are renowned to possess low porosity to demonstrate best charaterization. Without the presence of porosity or density analysis how can anyone be sure to achieve such results.
- These binders won’t be used as stand-alone materials. They shall further be mixed with inert material (of low porosity), at high temperatures, during mixing-compaction stages. Thus, the porosity of the final product, which will applied on the road pavement, will depend on other several factors. Probably a Marshall Test would be an additional assessment to consider.
Reviewer 3 Report
Most of the comments have been addressed in the revised manuscript. The overall quality of the manuscript has been improved.
Author Response
We thank the inputs and patience throughout the process. They've pushed us to this level.
