Extraction and Characterisation of Maltene from Virgin Asphalt as a Potential Rejuvenating Agent
, Salim T. Yousif 5, Mohd Khairul Idham Mohd Satar 3, Ramadhansyah Putra Jaya 6,7,*, Hassanain Radhi Radeef 3, Ahmed Salama Eltwati 8 and Ekarizan Shaffie 7
Round 1
Reviewer 1 Report
Thank you for the manuscript on the use of maltene as a rejuvenator in asphalt. There are a few elements that need further improvement.
1) Line 82: It is better to refer to highway agencies, transportation departments etc., rather than "the Department of Transportation (DOT) in many countries."
2) Dr. J. Claine Petersen has significantly contributed to bitumen chemistry. Also, a review of Lesueur has acted as a reference for various works (https://doi.org/10.1016/j.cis.2008.08.011). A reference to their works should be added. The following reference related to RAP and plastic utilization may also be useful (DOI:10.7250/bjrbe.2020-15.479)
3) Line 108: ‘Notified the need to discretely select the’ and Line 110-111: What is asphalt mobilization? Please clarify or improve.
4) The detail in section 2 seems unnecessary as an introduction to maltene is not needed. Their role as rejuvenators is already somewhat discussed in section 1. This section can be enhanced or alternatively sections 2 and 3 can be merged with most relevant information.
5) Section 3 heading level needs correction
6) Please clarify why petroleum ether was used to extract maltenes?
7) What methods were used to arrive at the results in Table 6?
8) Is it possible to add DSR master curves?
9) Table 1: Please only focus on the technique used by the authors.
10) The conventional and rheological properties of asphalt need to be included.
11) Figure 1 does not convey anything significant and can be removed.
12) Line 475-476: Please avoid the use of flexibility and rather focus on stiffness
13) Line 481-482: BBS only gives the maximum bond strength, whereas tensile strength based tests such as CPOT incorporate the loading rate in a more controlled manner. The author may refer to the following works related to bond strength https://doi.org/10.1016/j.conbuildmat.2019.02.093
Author Response
Reviewer (1)
Thank you for the manuscript on the use of maltene as a rejuvenator in asphalt. There are a few elements that need further improvement.
Response: Authors are grateful to the reviewer for his positive and encouraging comments
- Line 82: It is better to refer to highway agencies, transportation departments etc., rather than "the Department of Transportation (DOT) in many countries."
Response: Thanks for the comment.
Your suggestion was taken into consideration, where the sentence was edited to be as follow: (Please refer to the line 82, Page 2)
Currently, the highway agencies in many countries permit the use of RAP at a percentage range of 15–45% for the preparation of asphalt mixtures.
- J. Claine Petersen has significantly contributed to bitumen chemistry. Also, a review of Lesueur has acted as a reference for various works (https://doi.org/10.1016/j.cis.2008.08.011). A reference to their works should be added. The following reference related to RAP and plastic utilization may also be useful (DOI:10.7250/bjrbe.2020-15.479)
Response: Thanks for the suggestions and critical comments.
Both references have been cited based on your advice (Please refer to the line 51, Page 2 and line 150 Page 3)
Thus, various waste materials, such as RAP have been frequently used as a component in pavement mixtures [4, 5].
Maltene is composed of saturates, aromatics, and resins [43].
- Line 108: ‘Notified the need to discretely select the’ and Line 110-111: What is asphalt mobilization? Please clarify or improve.
Response: Thanks for the critical comments, the sentence was revised and improved to be as follow: (Please refer to the line 109-113, Page 3)
Nevertheless, Al-Saffar et al. [8] and Zaumanis et al. [28] notified that the rejuvenating agents should be carefully selected in order to achieve the desired short- and long-term properties of asphalt pavement performance. An example of a short-term criteria is the rapid diffusion into RAP triggers asphalt mobilisation [29], while one of the long-term criteria is the alteration of asphalt rheology to avoid fatigue and thermal cracking (prevent any rutting or softening issue) [29, 30].
- The detail in section 2 seems unnecessary as an introduction to maltene is not needed. Their role as rejuvenators is already somewhat discussed in section 1. This section can be enhanced or alternatively sections 2 and 3 can be merged with most relevant information.
Response: Thanks for the kind observation and suggestions for the improvement.
Section 1, 2 and 3 were merged and improved based on your advice. (Please refer to the page 2 and 3)
5) Section 3 heading level needs correction
Response: Thanks for the comment.
Some parts of this section were merged within section one while parts were merged section 2. Methodology, 2.1 Maltene extraction standard methods
6) Please clarify why petroleum ether was used to extract maltenes?
Response: Thanks for the question
The reason was mentioned in section 2.1, (please refer to the line 217-222, page 6)
In the present study, petroleum ether was selected as a solvent to separate asphaltene from maltene. Petroleum ether exhibits a low density, a boiling point range of 60–80 ℃, and contains light compounds with aliphatic hydrocarbons. Hence, a certain amount of petroleum ether was used to extract maltene from asphaltene. On the contrary, n-heptane (as an example) exhibits a higher density compared to petroleum ether and has a boiling point of over 98 ℃, making it difficult to be used as a solvent for extraction of maltene from VA
7) What methods were used to arrive at the results in Table 6?
Response: Thanks for the question
The results in Table 6 can be obtained using two methods:
- the nomographs for asphalt characteristics developed by Van der Poel (The shell bitumen handbook. Ice Publishing London, UK:: 2015; Vol. 514)
- Using BitProps software developed by Shell company.
8) Is it possible to add DSR master curves?
9) The conventional and rheological properties of asphalt need to be included.
Response: Thanks for the suggestions and comments.
To be honest, those tests have been included into another article which is under review now. Thus, if you want to add them in this article, I will do but I have to withdraw the other article first that will take time. At the same time, the journal gave me only seven days to submit the revised article. Thank you for your understanding
10) Table 1: Please only focus on the technique used by the authors.
Response: Thanks for the suggestions
The technique used for comparison purpose (ASTM D4124) was made in a Bold and several sentences were added in this section and focus on the method of using petroleum ether (Please refer to the Page 6 and 7)
11) Figure 1 does not convey anything significant and can be removed.
Response: Thanks again for the suggestions
The figure was deleted based on your suggestion
12) Line 475-476: Please avoid the use of flexibility and rather focus on stiffness
Response: Your invaluable comments are appreciated
The sentences were revised to be as follow: (Please refer to the lines 447-451, page 14)
Maltene was successfully separated from VA using petroleum ether. The GC-MS exhibited that the maltene contained polar and non-polar compounds, and the molecular weights of these compounds were much lower than that of asphalt binder. The maltene's spectra curve was near similar to that of asphalt, which indicated the potential of good compatibility between maltene and asphalt. Meanwhile, the addition of maltene to aged asphalt caused an increase in the aromatics and saturates content and a consequential decrease in the stiffness modulus. Moreover, the stiffness modulus of rejuvenated asphalt at high and low temperatures was restored with the addition of maltene signifying an improvement in features of aged asphalt after rejuvenation.
13) Line 481-482: BBS only gives the maximum bond strength, whereas tensile strength based tests such as CPOT incorporate the loading rate in a more controlled manner. The author may refer to the following works related to bond strength https://doi.org/10.1016/j.conbuildmat.2019.02.093
Response: Thanks for the kind observation and suggestions for the improvement.
The sentence was edited and improved to be as follow: (Please refer to the lines 455-457, page 14).
Future research should examine the surface-free energy (SFE), the binder bond strength (BBS) and Compression Pull-Off Test (CPOT) tests before and after ageing to understand the bonding and interactions between the aggregate and rejuvenated asphalt.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The article by Al-Saffar et al. deals with the extraction and characterization of maltene from virgin asphalt for evaluation as a potential rejuvenating agent. Although this study is done in a somewhat methodical way, the arrangement and presentation need to be improved substantially by addressing the points shown below:
1. Add some important quantitative data in the abstract.
2. Sections 1 and 2 should be seriously reduced in size. If the authors wanted to enthusiastically include all this information, then they can consider moving several paragraphs to supplementary material and some to results and discussion. Eventually, both these sections should be consolidated to one introduction section.
3. Section 3 is missing.
4. Section 4 and 5 should be put under the main heading “Materials and methods” or “Methodology” or “Experimental” choosing any one heading according to the journal style.
5. Figure 1 is not necessary as it simply displays the common GC-MS instrument.
6. Section 6 should be Results and discussion or just Results?
7. The little data in Table 2 and Table 5 can just be provided directly in the text and discussed. Please delete these two tables.
8. Why the GC-MS chromatogram is not provided?
9. Abbreviate seconds as “s” instead of sec or seconds in both text and tables.
10. Conclusion section should be provided in one single paragraph instead of hyphenated points.
11. In conclusion, “…an improvement in the flexibility and a consequential decrease in the stiffness modulus.” should be corrected as “…an improvement in the flexibility accompanied by a decrease in the stiffness modulus.”
12. When you combine sections 1 and 2 as one section by moving some to supplementary material and some to discussion, the number of references should be reduced accordingly.
13. There are many references that are not provided in the required journal style. Please double-check carefully.
Author Response
Reviewer (2)
The article by Al-Saffar et al. deals with the extraction and characterization of maltene from virgin asphalt for evaluation as a potential rejuvenating agent. Although this study is done in a somewhat methodical way, the arrangement and presentation need to be improved substantially by addressing the points shown below:
Response: Authors are grateful to the reviewer for his positive and encouraging comments
- Add some important quantitative data in the abstract.
Response: Thanks for the kind observation and suggestions for the improvement.
The abstract was edited and improved to be as follow: (Please refer to the line 51, Page 2 and lines 22-40, Page 1)
The wide application of Reclaimed Asphalt Pavement (RAP) is hindered due to the highly brittle nature of the material, which contributes a major factor towards cracking-related distresses. While the utilisation of rejuvenating agents has been shown to enhance the flexibility of RAP, they also trigger certain negative effects on the performance of asphalt mixtures. In view of this, potential rejuvenators should be able to alter the rheological properties of asphalts that limits fatigue issues and enhance the potential of low- temperature cracking. Therefore, this study aims to investigate the possibility of extraction and characterisation of maltene from virgin asphalt (VA) as a potential rejuvenating agent in RAP. Several physicochemical characteristics were carried out, including density, viscosity, Gas Chromatography-Mass Spectrometry (GC-MS), Fourier-Transform Infrared (FTIR) spectroscopy, CHNS elemental analysis, and Energy Dispersive X-ray (EDX) analysis. Finally, the stiffness modulus characteristics of the different types of asphalt binders were evaluated at low and high temperatures. The results demonstrated that maltene was successfully extracted from VA using petroleum ether. In addition, the GC-MS showed that the extracted maltene contained polar and non-polar compounds with low molecular weights compared to VA. Furthermore, the spectra curve of maltene was very similar to that of asphalt, indicating its compatibility with asphalt binder and prospective use. Finally, adding maltene to aged asphalt decreased stiffness values to 0.0063, 0.0499, and 0.0108 MPa, which are equivalent to VA values (0.0061, 0.0481, and 0.0104 MPa) at loading times of 1.0, 0.1, and 0.55 s, respectively. Meanwhile, the stiffness modulus characteristics at low-temperature were restored with the addition of maltene.
- Sections 1 and 2 should be seriously reduced in size. If the authors wanted to enthusiastically include all this information, then they can consider moving several paragraphs to supplementary material and some to results and discussion. Eventually, both these sections should be consolidated to one introduction section.
Response: Thanks again for the kind observation
The section 1 and 2 were merged and improved based on your suggestion
- Section 3 is missing.
That’s right, the sub heading was missing. However, this section was deleted and merged within section 1 and 2 as well
- Section 4 and 5 should be put under the main heading “Materials and methods” or “Methodology” or “Experimental” choosing any one heading according to the journal style.
Response: Your invaluable comments are appreciated;
We took your advice into our consideration; please check the article now.
- Figure 1 is not necessary as it simply displays the common GC-MS instrument.
Response: Thank you for your advice. The figure was deleted
- Section 6 should be Results and discussion or just Results?
Response: Thanks for the suggestions and critical comments.
The section was changed into “Results and discussion”
- The little data in Table 2 and Table 5 can just be provided directly in the text and discussed. Please delete these two tables.
Response: Your invaluable comments are appreciated;
Table 2 was deleted. However, we noted that it will be difficult for reader to understand the explanation if we deleted Table 5. Nevertheless, if you want to delete it, I will do
- Why the GC-MS chromatogram is not provided?
Response: Thanks for the question, the software used in the GC-MS doesn’t provide chromatogram
- Abbreviate seconds as “s” instead of sec or seconds in both text and tables.
Response: Thanks for the critical comments.
All “sec” abbreviates were changed into “s”
The corrections in both text and tables regarding this issue were highlighted in RED color
- Conclusion section should be provided in one single paragraph instead of hyphenated points.
Response: Your invaluable comments are appreciated;
The conclusion was re-written and re-arranged as following: (Please refer to the lines 440-458, page 14)
This present study aimed to scrutinise the feasibility of extraction and characterisation of maltene to be used as a rejuvenating agent. The significant outcomes obtained from this study are summarised below:
Maltene was successfully separated from VA using petroleum ether. The GC-MS exhibited that the maltene contained polar and non-polar compounds, and the molecular weights of these compounds were much lower than that of asphalt binder. The maltene's spectra curve was near similar to that of asphalt, which indicated the potential of good compatibility between maltene and asphalt. Meanwhile, the addition of maltene to aged asphalt caused an increase in the aromatics and saturates content and a consequential decrease in the stiffness modulus. Moreover, the stiffness modulus of rejuvenated asphalt at high and low temperatures was restored with the addition of maltene signifying an improvement in features of aged asphalt after rejuvenation.
Based on the laboratory tests, several recommendations are suggested for extensive research work in the future: (a) Research on the effect of short and long-term ageing on the physical, rheological and microstructure characteristics of aged asphalt incorporating maltene is recommended, (b) Future research should examine the surface-free energy (SFE), the binder bond strength (BBS) and Compression Pull-Off Test (CPOT) tests before and after ageing to understand the bonding and interactions between the aggregate and rejuvenated asphalt.
- In conclusion, “…an improvement in the flexibility and a consequential decrease in the stiffness modulus.” should be corrected as “…an improvement in the flexibility accompanied by a decrease in the stiffness modulus.”
Response: Thanks for the comments and the suggestion is well-taken care.
The sentence was revised and improved, (Please refer to the lines 440-458, page 14)
the addition of maltene to aged asphalt caused an increase in the aromatics and saturates content and a consequential decrease in the stiffness modulus. Moreover, the stiffness modulus of rejuvenated asphalt at high and low temperatures was restored with the addition of maltene signifying an improvement in features of aged asphalt after rejuvenation.
- When you combine sections 1 and 2 as one section by moving some to supplementary material and some to discussion, the number of references should be reduced accordingly.
Response: Thanks for the comments and your suggestion is well-taken care.
Several references were deleted. Noting that we added 2 references based on the advice of the first reviewer.
- There are many references that are not provided in the required journal style. Please double-check carefully.
Response: Thanks again for the valuable suggestion,
All the references were checked and rectified again to be as the journal style.
Author Response File: Author Response.pdf
Reviewer 3 Report
Attractive manuscript related to the extraction and characterisation of maltene from virgin asphalt as a potential rejuvenating agent for reclaimed asphalt pavement (RAP).
In general, the manuscript is well presented, but some details must be clarified or corrected/completed:
1. Line 197: where is written “compared to asphalts” did you want to write “compared to asphaltenes”?
2. Lines 211/212: the section title “3. Maltene Extraction” is not in the correct position;
3. Line 246: please correct the word “difficlut”;
4. Line 261: the symbol for the hour is “h” and not “hr”;
5. Figure 3: it seems that a legend is missing in the XX axle;
6. Table 4: please include the unit in the “Area” column;
7. Line 462: please correct the unit “Mpa”;
8. Section “6.6 Aged binder flexibility restoration”: can you include the high and low-temperatures calculations (as it is referred to in section 5.7)?
9. Section “7. Conclusions”: these conclusions seem too general. You can include some numbers;
10. In this section 7 or where appropriate: can you add some information about the limitations of the study and recommendations/suggestions for future works?
11. You should also include some discussion in light of results obtained by other researchers (if you find some similar and recent ones);
12. In “References”, you can include the digital object identifier (DOI) for all references where available (as “encouraged” in the “Instructions for Authors”).
Author Response
Reviewer (3)
Attractive manuscript related to the extraction and characterisation of maltene from virgin asphalt as a potential rejuvenating agent for reclaimed asphalt pavement (RAP).
In general, the manuscript is well presented, but some details must be clarified or corrected/completed:
Response: Authors are grateful to the reviewer for his positive and encouraging comments
- Line 197: where is written “compared to asphalts” did you want to write “compared to asphaltenes”?
Response: Thanks for the comments
It should be “asphaltene”. However, this sentence was deleted from the new version of the article, because that the second reviewer suggested to shorten the introduction.
- Lines 211/212: the section title “3. Maltene Extraction” is not in the correct position;
Response: Thanks for the kind observation. Nevertheless, this section was deleted and merged within section 1 and 2
- Line 246: please correct the word “difficlut”;
Response: Thanks again for the kind observation
The mistake was corrected to be as following (please refer to the line 222, page 6)
On the contrary, n-heptane (as an example) exhibits a higher density compared to petroleum ether and has a boiling point of over 98 ℃, making it difficult to be used as a solvent for extraction of maltene from VA
- Line 261: the symbol for the hour is “h” and not “hr”;
Response: Thanks for the suggestion
The mistake was rectified, (please refer to the line 238, page 6)
The mixture was then transferred into a water bath at 50 °C for 2 h with continuous stirring until the soluble fraction was completely dissolved
- Figure 3: it seems that a legend is missing in the XX axle;
Response: Thanks again for the kind observation
The mistake was rectified (please refer to the Figure 4)
- Table 4: please include the unit in the “Area” column;
Response: thanks for the suggestion
The unit (%) was included in the column
- Line 462: please correct the unit “Mpa”;
Response: thanks again for the suggestion and the mistake was rectified (Please refer to the line 435, page 13)
The same changings happened at low-temperature where the stiffness values of aged asphalt were 74.68, 169.3 and 93.01 MPa and restored be 72.37, 174.9 and 92.48 MPa with the addition of maltene.
- Section “6.6 Aged binder flexibility restoration”: can you include the high and low-temperatures calculations (as it is referred to in section 5.7)?
Response: Your invaluable comments are appreciated;
The data in this section was taken directly from BitProps software that developed by Shell company.
- Section “7. Conclusions”: these conclusions seem too general. You can include some numbers;
Response: Thanks for the comments and your suggestion is well-taken care.
The conclusion was re-written and re-arranged as following: (Please refer to the lines 440-458, page 14)
This present study aimed to scrutinise the feasibility of extraction and characterisation of maltene to be used as a rejuvenating agent. The significant outcomes obtained from this study are summarised below:
Maltene was successfully separated from VA using petroleum ether. The GC-MS exhibited that the maltene contained polar and non-polar compounds, and the molecular weights of these compounds were much lower than that of asphalt binder. The maltene's spectra curve was near similar to that of asphalt, which indicated the potential of good compatibility between maltene and asphalt. Meanwhile, the addition of maltene to aged asphalt caused an increase in the aromatics and saturates content and a consequential decrease in the stiffness modulus. Moreover, the stiffness modulus of rejuvenated asphalt at high and low temperatures was restored with the addition of maltene signifying an improvement in features of aged asphalt after rejuvenation.
Based on the laboratory tests, several recommendations are suggested for extensive research work in the future: (a) Research on the effect of short and long-term ageing on the physical, rheological and microstructure characteristics of aged asphalt incorporating maltene is recommended, (b) Future research should examine the surface-free energy (SFE), the binder bond strength (BBS) and Compression Pull-Off Test (CPOT) tests before and after ageing to understand the bonding and interactions between the aggregate and rejuvenated asphalt.
- In this section 7 or where appropriate: can you add some information about the limitations of the study and recommendations/suggestions for future works?
Response: Thanks for the comments and your suggestion is well-taken care.
The limitations and the recommendation were included at the end of the conclusion
- In “References”, you can include the digital object identifier (DOI) for all references where available (as “encouraged” in the “Instructions for Authors”).
Response: Thanks for your suggestion
DOI was added for all references where available
Author Response File: Author Response.pdf
Reviewer 4 Report
The paper is useful but has been written like an experimental report. The language is okay, but I suggest authors overhaul the paper to make it a research study.
The sectioning of the paper shall be revised.
2. 2. Maltene as a Potential Rejuvenator
It seems odd here; it can be called ‘background.’
Section 3 is missing; it should be ‘Experimental’ followed by 3.1. ‘Materials’ and 3.2.’ Testing Methods’ or ‘Methodology’
Schematics for Determination of the Asphalt to Petroleum Ether Ratio and Extraction and Recovery of Maltene should be included. It will help explain these sections. Presently comprehension is difficult.
Flowchart for experimental work shall be included
Characterization of Maltene should be part of the experimental section. No separate section is required.
Fig.2, the captions for each figure are required.
Error bars in Fig. 3 required
Fig.1 is useless. If you are considering adding such figures, then figures for the FTIR spectrometer should also be added. Hence, avoid such figures. Instead, show the readers the images of experimental work performed to determine viscosity, etc.
Draw more figures from table 3. There are many figures for analytical characterizations but fewer figures showing macro-characterizations. Also, draw figures from Table 6. Also, show error bars.
What is Area in Table 4?
The conclusions are short. It should be concise but pithy.
The section ‘Results’ should be results and discussion’ instead.
6.6 Aged binder flexibility restoration should be moved above analytical characterizations
Author Response
Reviewer (4)
- The sectioning of the paper shall be revised.
Response: Thanks for the comments and your suggestion is well-taken care.
The sections were revised and improved based on your suggestion. For example: section 1 and section 2 were merged and several sentences were deleted. After that, section three was merged within section 2. Also, the results section was changed into results and discussion. Furthermore, the flowchart was added
- Maltene as a Potential Rejuvenator
It seems odd here; it can be called ‘background.’
Response: Thanks for the kind observation
This section was merged within section 1
- Section 3 is missing; it should be ‘Experimental’ followed by 3.1. ‘Materials’ and 3.2.’ Testing Methods’ or ‘Methodology’
Response: Thanks again for the kind observation
The mistakes were rectified please refer to the article after revision.
- Schematics for Determination of the Asphalt to Petroleum Ether Ratio and Extraction and Recovery of Maltene should be included. It will help explain these sections. Presently comprehension is difficult.
Response: Your invaluable comments are appreciated; Schematic was added (please refer to the figure 2, page 7)
Figure 2. The procedure for extracting maltene
- Flowchart for experimental work shall be included
Response: Your invaluable suggestion is appreciated;
The flowchart was added as the following:
|
Petroleum Ether |
|
Aged asphalt |
|
Asphalt binder |
|
Asphaltene |
|
Maltene |
|
Viscosity |
|
Density |
|
EDX |
|
Stiffness modulus at high and low temperatures |
|
CHNS |
|
GCMS |
|
FTIR |
|
Rejuvenated asphalt |
- Characterization of Maltene should be part of the experimental section. No separate section is required.
Response: Thanks for the kind observation
The mistake was rectified and the characterisation of maltene has become a part of the methodology section
- 2, the captions for each figure are required.
Response: Thanks for the comments and your suggestion is well-taken care.
|
|
|
||||
|
(A) 1g asphalt: 1X mL solvent |
(B) 1g asphalt: 2X mL solvent |
||||
|
|||||
|
(C) 1g asphalt: 3 X mL solvent |
|
||||
Figure 3. Separation of asphaltene from maltene using different volumetric percentages
- Error bars in Fig. 3 required
Response: Your invaluable comment is appreciated;
The error bars were included in the figure.
- 1 is useless. If you are considering adding such figures, then figures for the FTIR spectrometer should also be added. Hence, avoid such figures. Instead, show the readers the images of experimental work performed to determine viscosity, etc.
Response: Thanks for the comments
The figure was deleted
- What is Area in Table 4?
Response: Thanks for the question
It is a reflection of the amount (%) of a specific analyte that's present. And the unit (%) was added in the column
- The conclusions are short. It should be concise but pithy.
Response: Thanks for the comments and your suggestion is well-taken care.
Conclusion was re-written and re-arranged as following: (Please refer to the lines 440-458, page 14)
This present study aimed to scrutinise the feasibility of extraction and characterisation of maltene to be used as a rejuvenating agent. The significant outcomes obtained from this study are summarised below:
Maltene was successfully separated from VA using petroleum ether. The GC-MS exhibited that the maltene contained polar and non-polar compounds, and the molecular weights of these compounds were much lower than that of asphalt binder. The maltene's spectra curve was near similar to that of asphalt, which indicated the potential of good compatibility between maltene and asphalt. Meanwhile, the addition of maltene to aged asphalt caused an increase in the aromatics and saturates content and a consequential decrease in the stiffness modulus. Moreover, the stiffness modulus of rejuvenated asphalt at high and low temperatures was restored with the addition of maltene signifying an improvement in features of aged asphalt after rejuvenation.
Based on the laboratory tests, several recommendations are suggested for extensive research work in the future: (a) Research on the effect of short and long-term ageing on the physical, rheological and microstructure characteristics of aged asphalt incorporating maltene is recommended, (b) Future research should examine the surface-free energy (SFE), the binder bond strength (BBS) and Compression Pull-Off Test (CPOT) tests before and after ageing to understand the bonding and interactions between the aggregate and rejuvenated asphalt.
- The section ‘Results’ should be results and discussion’ instead.
Response: thank you for the suggestion
The section was changed into “results and discussion”
- Aged binder flexibility restoration should be moved above analytical characterizations
Response: Your invaluable comment is appreciated;
This sub section was changed into “3.6 Stiffness at high and low temperatures”, we put it after maltene Characterisation results due to that the rejuvenation process have taken place after maltene extraction. In addition, we think that the arrangement now became very clear after including the flowchart in the article.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors have addressed most of the comments satisfactorily. Figure 1 raises the same question about rheology and low and high temperature properties that I highlighted in firs review. The comment of authors is understandable. However, few rheological results at certain low and high test temperature should be added (Or other results of maltenes enhanced asphalt to be should added). It is easier than adjusting all the discussions in paper.
Author Response
Reviewer (1)
The authors have addressed most of the comments satisfactorily. Figure 1 raises the same question about rheology and low and high temperature properties that I highlighted in firs review. The comment of authors is understandable. However, few rheological results at certain low and high test temperature should be added (Or other results of maltenes enhanced asphalt to be should added). It is easier than adjusting all the discussions in paper.
Response: Your invaluable comments are appreciated;
New results have been included, (please refer to the Pages 14 and 15, line 450-471), knowing that the outcomes were supported by references
On the other hand, the complex modulus and phase angles of asphalt binder samples at 0.1 Hz, 1 Hz and 10 Hz are shown in Figures 7 and 8. The complex modulus of asphalt represents its resistance to deformation under shear stress, while the phase angle represents the viscous response of the asphalt to the shear deformation [62]. From the figures, it can be realized that the complex modulus values of the aged asphalt were high than values of virgin and rejuvenated asphalts. This means that the aging process made the asphalt binder become stiff to a large extent. Meanwhile, the addition of maltene rejuvenator softened the aged asphalt for all frequencies. Thus, the values of virgin and rejuvenated asphalt binders appear relatively close to each other in the table indicating an improvement in rheological properties after rejuvenation.
In contrast, the aged asphalt exhibited the lowest phase angle values at the different frequencies compared with virgin and rejuvenated asphalt binders. A lower phase angle asphalt binder typically has higher elasticity and performs better in recovering shear deformation. Meanwhile, the asphalt binder had a substantial an increase in the phase angle after including maltene. This indicated that the addition of maltene improved the viscous components, and rejuvenated the viscoelastic properties of the aged asphalt binders to be close to the original level. The conclusion is consistent with Cavalli et al. [63] who reported that aged asphalt with rejuvenating agent exhibited lower rutting resistance relative to aged asphalt without rejuvenating agent.
Figure 7: Complex modulus for different asphalt samples
Figure 8: Phase angle for different asphalt samples
Author Response File: Author Response.pdf
Reviewer 2 Report
The authors have satisfactorily addressed all the comments raised by reviewers and therefore I recommend acceptance of this article for publication in Sustainability.
Author Response
Reviewer (2)
The authors have satisfactorily addressed all the comments raised by reviewers and therefore I recommend acceptance of this article for publication in Sustainability.
Response: Your invaluable comments are appreciated; thank you so much
Author Response File: Author Response.pdf
Reviewer 4 Report
Insert references in section 3.4, 3.5, and 3.6.
Put at least 8 figures in the manuscript. The authors can present the table given in tables to construct more figures. An ideal paper should have adequate number of figures and should be referenced adequately as well. I found no references in FTIR section.
The paper should go one more round of review. This is my recommendation.
Author Response
Reviewer (4)
- Insert references in section 3.4, 3.5, and 3.6.
Response: Your invaluable comments are appreciated;
The references were included in the sections 3.4, 3.5, and 3.6 (please refer to the pages 12 and 13)
3.4 Elemental Analysis
EDX is a useful tool used to determine the elements contained in the asphalt binder [58]. …………..…… Notably, the C value examined using EDX was higher than the value retrieved from CHNS analyser, mainly because EDX only detected elements present on the material surface [59]. Hence, it differed from the elements' percentages from the elemental analysis.
3.5 Fourier Transform Infrared (FTIR)
Figure 6 presents the FTIR spectra of maltene………….……. Meanwhile, the 2851 cm-1 and 2919.7 cm-1 absorption bands indicate the C-H stretching vibration. Based on the results, it can be perceived that the maltene spectra curve is very near to the normal asphalt binder. This undoubtedly indicates the potential for good compatibility of maltene in the binders [40].
3.6 Stiffness at high and low temperatures
Table 5 shows that maltene has diminished the ageing effect of aged asphalt by decreasing the stiffness to be similar to that of the virgin asphalt. ………………………… The same changings happened at low-temperature where the stiffness values of aged asphalt were 74.68, 169.3 and 93.01 MPa and restored be 72.37, 174.9 and 92.48 MPa with the addition of maltene. Similarly, Zhang et al. [60] and Zhang et al. [61] asserted that increased stiffness of asphalt can deteriorate the low temperature cracking resistance, while the addition of rejuvenator can improve the low-temperature cracking resistance of aged asphalt.
- Put at least 8 figures in the manuscript. The authors can present the table given in tables to construct more figures. An ideal paper should have adequate number of figures and should be referenced adequately as well. I found no references in FTIR section.
Response: Thanks for the comments and your suggestion is well-taken care.
The number of figures was increased to be 8 figures with new results and references (please refer to the page 8 , as well as page 14 and 15)
Furthermore, the complex modulus and phase angle of asphalt binder were also determined depending on the mean of the hottest seven-day period in the last five years in Mosul-Iraq using BitProps software shown in Figure 3
Figure 3. BitProps software
----
On the other hand, the complex modulus and phase angles of asphalt binder samples at 0.1 Hz, 1 Hz and 10 Hz are shown in Figures 7 and 8. The complex modulus of asphalt represents its resistance to deformation under shear stress, while the phase angle represents the viscous response of the asphalt to the shear deformation [62]. From the figures, it can be realized that the complex modulus values of the aged asphalt were high than values of virgin and rejuvenated asphalts. This means that the aging process made the asphalt binder become stiff to a large extent. Meanwhile, the addition of maltene rejuvenator softened the aged asphalt for all frequencies. Thus, the values of virgin and rejuvenated asphalt binders appear relatively close to each other in the table indicating an improvement in rheological properties after rejuvenation.
In contrast, the aged asphalt exhibited the lowest phase angle values at the different frequencies compared with virgin and rejuvenated asphalt binders. A lower phase angle asphalt binder typically has higher elasticity and performs better in recovering shear deformation. Meanwhile, the asphalt binder had a substantial an increase in the phase angle after including maltene. This indicated that the addition of maltene improved the viscous components, and rejuvenated the viscoelastic properties of the aged asphalt binders to be close to the original level. The conclusion is consistent with Cavalli et al. [63] who reported that aged asphalt with rejuvenating agent exhibited lower rutting resistance relative to aged asphalt without rejuvenating agent.
Figure 7: Complex modulus for different asphalt samples
Figure 8: Phase angle for different asphalt samples
Author Response File: Author Response.pdf
Round 3
Reviewer 4 Report
Version for BitProps software shall be provided, no need to show the screenshot.
Include SEM images with EDX analysis.
The result and discussion section shall be extended. It seem of same length as that of material and testing methods.
Conclusions shall be revised. Its too short for a scientific paper publishing in high impact factor.
Author Response
Reviewer (4)
- Version for BitProps software shall be provided, no need to show the screenshot.
Response: Thanks for the comments
The screenshot was deleted and BitProps version was provided (please refer to the page 11, line 321-322)
Furthermore, the complex modulus and phase angle of asphalt binder were also determined depending on the mean of the hottest seven-day period in the last five years in Mosul-Iraq using BitProps V2 software developed by G. Rowe and M. Sharrock.
- Include SEM images with EDX analysis.
Response: Your invaluable comments are appreciated;
We don’t have the SEM image, we have only the data analysis that were included in the research. (Please refer to the table 4, page 12)
Table 4: CHNS & EDX analysis of maltene
|
Test |
C (%) |
H (%) |
N (%) |
S (%) |
O (%) |
|
EDX |
93.6 |
- |
- |
5.5 |
0.8 |
|
CHNS |
82.80 |
11.61 |
0.48 |
5.10 |
- |
- The result and discussion section shall be extended.
Response: Your invaluable comments are appreciated;
Several paragraphs were included, please refer to the lines (425-427), (443-445), (449-467)
Based on the results, it can be perceived that the maltene spectra curve is very near to the normal asphalt binder. This undoubtedly indicates the potential for good compatibility of maltene in the binders [40].
The same changings happened at low-temperature where the stiffness values of aged asphalt were 74.68, 169.3 and 93.01 MPa and restored be 72.37, 174.9 and 92.48 MPa with the addition of maltene. Similarly, Zhang et al. [60] and Zhang et al. [61] asserted that increased stiffness of asphalt can deteriorate the low temperature cracking resistance, while the addition of rejuvenator can improve the low-temperature cracking resistance of aged asphalt.
On the other hand, the complex modulus and phase angles of asphalt binder samples at 0.1 Hz, 1 Hz and 10 Hz are shown in Figures 6 and 7. The complex modulus of asphalt represents its resistance to deformation under shear stress, while the phase angle represents the viscous response of the asphalt to the shear deformation [62]. From the figures, it can be realized that the complex modulus values of the aged asphalt were high than values of virgin and rejuvenated asphalts. This means that the aging process made the asphalt binder become stiff to a large extent. Meanwhile, the addition of maltene rejuvenator softened the aged asphalt for all frequencies. Thus, the values of virgin and rejuvenated asphalt binders appear relatively close to each other in the table indicating an improvement in rheological properties after rejuvenation.
In contrast, the aged asphalt exhibited the lowest phase angle values at the different frequencies compared with virgin and rejuvenated asphalt binders. A lower phase angle asphalt binder typically has higher elasticity and performs better in recovering shear deformation. Meanwhile, the asphalt binder had a substantial an increase in the phase angle after including maltene. This indicated that the addition of maltene improved the viscous components, and rejuvenated the viscoelastic properties of the aged asphalt binders to be close to the original level. The conclusion is consistent with Cavalli et al. [63] who reported that aged asphalt with rejuvenating agent exhibited lower rutting resistance relative to aged asphalt without rejuvenating agent.
- Conclusions shall be revised. Its too short for a scientific paper publishing in high impact factor
Response: Thanks for the comments and your suggestion is well-taken care.
The conclusion was revised (please refer to the lines 472-495)
This present study aimed to scrutinise the feasibility of extraction and characterisation of maltene to be used as a rejuvenating agent. The significant outcomes obtained from this study are summarised below:
Maltene was successfully separated from VA using petroleum ether. The GC-MS exhibited that the maltene contained polar and non-polar compounds, and the molecular weights of these compounds were much lower than that of asphalt binder. The maltene's spectra curve was near similar to that of asphalt, which indicated the potential of good compatibility between maltene and asphalt. Meanwhile, the addition of maltene to aged asphalt caused an increase in the aromatics and saturates content and a consequential decrease in the stiffness modulus. Moreover, the stiffness modulus of rejuvenated asphalt at high and low temperatures was restored with the addition of maltene signifying an improvement in features of aged asphalt after rejuvenation. Meanwhile, the addition of maltene enhanced the viscous components, and rejuvenated the viscoelastic characteristics of the aged asphalt binders to be close to the original level. These outcomes were verified using the complex modulus and phase angle measurements.
Based on the laboratory tests, several recommendations are suggested for extensive research work in the future: (a) Extraction and characterisation of maltene from more than one resource of asphalt is suggested, (b) Research on the effect of short and long-term ageing on the physical, rheological and microstructure characteristics of aged asphalt incorporating maltene is recommended, (c) Future research should examine the surface-free energy (SFE), the binder bond strength (BBS) and Compression Pull-Off Test (CPOT) tests before and after ageing to understand the bonding and interactions between the aggregate and rejuvenated asphalt.
Author Response File: Author Response.pdf
