Research on the Fracture Characteristics of Asphalt Mixtures in High Altitude and Cold Regions with Large Temperature Differences
Round 1
Reviewer 1 Report
The authors presented an experimental investigation by simulating cold regions with large temperature difference on the fracture characteristics of asphalt mixtures. The thermal stress restrained specimen test and low temperature bend test were used.
The paper is well written and well structured.
The research significance is well explained in the introduction section.
The paper could have been better if a prototype or a pavement section was realized in the field and subjected to real environments conditions and its performance evaluated.
The quality of the figures 1 to 3 could be improved.
Author Response
Point 1:The authors presented an experimental investigation by simulating cold regions with large temperature difference on the fracture characteristics of asphalt mixtures. The thermal stress restrained specimen test and low temperature bend test were used.
Response 1: The article has been improved according to the comment.
Point 2:The paper is well written and well structured.
Response 2: The article has been improved according to the comment.
Point 3:The research significance is well explained in the introduction section.
Response 3: The article has been improved according to the comment.
Point 4:The paper could have been better if a prototype or a pavement section was realized in the field and subjected to real environments conditions and its performance evaluated.
Response 4: The study referred to the climatic environment of the Qinghai-Tibet Plateau, and follow-up studies will be conducted at the site.
Point 5:The quality of the figures 1 to 3 could be improved.
Response 5: The article has been improved according to the comment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Comments for author File: Comments.docx
Author Response
Point 1: This study aims at selecting the best-performing asphalt concrete mix at temperature conditions mimicking cold regions with significant temperature gaps. A total of 6 asphalt concrete mixtures were tested with conventional laboratory setups (e.g., Marshall, TSRST, Beam Bending, etc.) to examine their cracking resistance characteristics. First, it is hard to see any correlation between the field and laboratory temperature conditions. The authors must try to explain how the selected temperature ranges serve the purposes of the study. Referencing the standards is not sufficient. Second, It is common knowledge that a higher binder content can boost crack resistance. Is there any reason the authors did not test the impact of binder contents on the cracking performance? Also, other modified asphalt types than SBS are known to perform better in the crack-prone environment. Finally, the results presented in tables and charts must be accompanied by the author's deep analysis, not a simple description of the data, almost equivalent to a data dump.
Response 1: The article has been modified according to the comment. The study referred to the temperature conditions of the Tibetan Plateau. The crack resistance of asphalt mixture is also maintained at the optimal level under the condition of the optimum amount of asphalt. This study has not carried out the research on the performance of asphalt mixture under the condition of different amount of asphalt.
Point 2: A term is confusing: change high region to high altitude region
Response 2: The term has been modified according to the comment.
Point 3: Line 26: It is nothing new to say that "In TSRST, the frost-break temperature was the best indicator of the material crack resistance and directly correlated with the low-temperature cracking of asphalt pavement, so it could be used as the evaluation index of low-temperature performance of asphalt mixtures." Please elaborate on the other merits of TSRST and other test methods.
Response 3: In this study, TSRST was used to analyze the crack resistance of asphalt mixture at low temperature, and the relevant conclusions were obtained. The comparative analysis of TSRST and other tests was not carried out in this study.
Point 4: Line 30: Please define AC.
Response 4: The term has been modified according to the comment.
Point 5: Line 38: redefine the "keywords"
Response 5: The term has been modified according to the comment.
Point 6:Line 78: Please elaborate on "The temperature fatigue of asphalt mixtures."
Response 6: This part is a summary of previous research results and represents the development of research work. This paper does not give a more detailed explanation.
Point7: Line 153: Authors noted that "there is no in-depth study on the fracture characteristics of asphalt mixtures under said conditions." However, this reviewer is not convinced that this study has thoroughly investigated fracture.
Response 7: This argument has been revised
Point 8:Line 167: Please define "Matric Asphalt." It sounds like unmodified asphalt, though.
Response 8: "Matric Asphalt." is” unmodified asphalt”, It is defined in the article.
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Point 9: Line 191: What is the point of running the Marshall Stability test? It is conducted at room temperature and way higher than the temperatures in cold regions.
Response 9: Marshall stability test is to verify the basic properties of asphalt mixture.
Point 10: Line 297: Check the spelling.
Response 10: The term has been modified according to the comment.
Point 11: Line 309: Is it true that SMA has a denser skeleton than AC mixes that are usually densely graded?
Response 11: According to the test results in Table 4, the porosity of SMA-13 was lower than that of AC-13 and AC-16. SMA has a denser skeleton than AC mixes.
Point 12: Line 348: "At -20℃, both AC-13 and AC-16 break. At low temperature, the load-displacement curves of the three kinds of asphalt mixtures differ greatly" does not convey any meaning. What makes authors claim that is the case? Also, It is not making sense that at non-freezing temperatures, all the mixtures show the same flexural resistance.
Response 12: This argument has been revised.
Point 13: Line 354: It is nothing new to report that SMA has a higher bending performance than the AC counterpart. Please note the actual gap (% difference) in their performance.
Response 13: This argument has been revised.
Point 14: Line 380: In Figure 8, how many sample replicates were used for each mixture type? If possible, it must be noted in other figures.
Response 14: In Figure 8, 4 sample replicates were used for each mixture type. The average value of test results is adopted in the figure.
Author Response File: Author Response.docx
Reviewer 3 Report
- Overall, the language of the manuscript is very poor.
- What do you mean by high regions?
- The abstract should be improved. It is way too long. Especially the flow of the language. I should start with a short introduction, objectives, and major conclusions.
- Your introduction needs more information about performance. I missing some general information regarding the performance of asphalt mixtures, such as https://doi.org/10.1016/j.conbuildmat.2017.07.164 and doi.org/10.1080/14680629.2021.1908408.
- Please state clearly your objectives.
- You don`t have real conclusions. They should be concise not like a discussion.
Author Response
Point 1: Overall, the language of the manuscript is very poor.
Response 1: The article has been improved according to the comment.
Point 2: What do you mean by high regions?
Response 2: The article has been improved according to the comment, change high region to high altitude region.
Point 3:The abstract should be improved. It is way too long. Especially the flow of the language. I should start with a short introduction, objectives, and major conclusions.
Response 3: The article has been improved according to the comment.
Point 4:Your introduction needs more information about performance. I missing some general information regarding the performance of asphalt mixtures, such as https://doi.org/10.1016/j.conbuildmat.2017.07.164 and doi.org/10.1080/14680629.2021.1908408.
Please state clearly your objectives.
Response4: Some information about the properties of asphalt mixture has been modified.
Point 5:You don`t have real conclusions. They should be concise not like a discussion.
Response5: This paper mainly studies the fracture Characteristics of Asphalt Mixtures, the conclusion is more likely to be a summary of the law, its purpose is to provide guidance for the selection of asphalt pavement surface materials and the optimization design of mixtures in high altitude and cold regions with large temperature differences.
Round 2
Reviewer 2 Report
1. The revised manuscript has not accounted for the reasonable comments, such as too long abstract and weak conclusions.
2. The authors need to make a major effort to rewrite the manuscript (too many repeated terms, lengthy and meaningless statements, and confusing statements)
3. This work can better focus on the evaluations of TSRST (frost-break temperature) and bending test (flexural strength and fracture toughness) with a well-organized asphalt and asphalt mixture designs. Most of confusions stem from the ill-structured presentation.
4. The test results must be interpreted and clearly stated. For instance, what does the higher frost-break temperature imply? Why flexural strength and fracture toughness increase at first and decrease as the temperature increases?
5. When the authors stated the climate conditions in the high altitude and cold regions were simulated with large temperature gaps, there was no clear justification for the test of a variety of asphalt mixtures. Is this material group including the most common asphalt mixtures specific to those regions? It seems that No.90 matrix asphalt (unmodified asphalt) and SBS-modified asphalt have been widely used in the country for curbing the low temperature cracking. If so, the authors need to explain why those
materials have not been so effective and what is the main issue with them.
6. In Table 7, What are the Principal Components? How does the Principal Component 2 correspond with the Frost-break temperature?
7. As a results of sensitivity analysis of asphalt type, mixture type and cooling rate on the fracture-frost temperature, what is the conclusion the authors drew other than all three inputs affect the fracture -frost temperature individually?
Author Response
Response 1: The article has been further modified.
Response 2: The article has been further modified.
Response 3: The article has been further modified.
Response 4: Part of the article has been modified according to the comment.
Response 5: The article has been further modified.
Response 6: The Principal Components have been defined
Response 7: Unfortunately, for the opinions of experts, this article did not do the corresponding test.
Author Response File: Author Response.docx
Reviewer 3 Report
I feel that the authors didn`t take my comments seriously and that I spent more time reading this manuscript than the authors fixing it.
The language is far below the average.
Author Response
Thanks very much for the valuable opinions and apologize for the lack of modification.
Part of the article has been modified according to the comment.
Round 3
Reviewer 3 Report
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