Investigation on Fracture Performance of Hot-Mix Asphalt with Reclaimed Asphalt Pavement under Fatigue Loading

Round 1

Reviewer 1 Report

The authors investigated the fatigue cracking behaviors of hot mix asphalt (HMA) with 12 different content of reclaimed asphalt pavement (RAP), using an Overlay Tester. The innovative aspect of this study is that the energy dissipated during the load-controlled test is used to analyze fracture behaviors. The results showed that with the increase of RAP content, the monotonic fracture behaviors of HMA, were significantly deteriorated at both  -10°C and  25°C. RAP prolonged the fatigue life at 25°C but opposite conclusions were made at -10°C. At -10°C, the incorporation of RAP significantly reduced the dissipated energy and  the cumulative energy, indicating the fatigue cracking resistance was weakened. The developments of the dissipated energy and the cumulative energy were consistent with the fatigue life results determined as the cycle number at the end of OT test. 

Author Response

Authors appreciated the comments on this manuscript.

Reviewer 2 Report

The presented manuscript “Investigation on Fracture Performance of Hot Mix Asphalt with Reclaimed Asphalt Pavement under Fatigue Loading” contains good findings. I think that this manuscript requires some changes in following areas:

·         Abstract: Need to address a) need of this work, b) novelty, c) methodology suggested, d) results obtained (numerical).

·         Introduction section has been written well including the literature work and scope of the current work with novelty.

·         Remove the section 2. Add the paragraph as last paragraph of section 1.

·         Add compositions of the used material in tables.

·         Modify the captions of figure 1 and 2.

·         Line 192: Add full form of OT. Do this for all headings

·         The obtained results are encouraging. However, justify the finding with proper technical reason and relevant literature source

·         Re-check the reference style. It should be as per the journal requirement.

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

1.     The research background should be provided in the abstract section.

2.     What percentage of RAP materials was used in this study? It should be mentioned in the abstract section.

3.     Titles should not be presented at the bottom of the page. They should be corrected.

4.     What is the reason for using these RAP percentages in this research?

5.     Why Superpave tests were not used in this study?

6.     The authors should present more future directions in the conclusion section. They can recommend examining the effect of various anti-stripping agents, polymers and nanomaterials on the performance of asphalt mixtures in the future: doi.org/10.1080/10916466.2019.1608237, doi.org/10.3221/IGF-ESIS.53.17, doi.org/10.1080/10916466.2016.1270301, doi.org/10.1080/10298436.2022.2072500.

7.     Enrich the quality of the figures in this research.

8.     Language revision throughout the manuscript is needed to remove grammatical errors and make the language more technical.

9.     What is the limitation of this research? It can be presented at the end of the conclusion section.

Language revision throughout the manuscript is needed to remove grammatical errors and make the language more technical.

Author Response

The writing quality was checked and appropriate revisions were made.

Responses to the reviewer's comments can be seen in the attachment.

Author Response File: Author Response.docx

Reviewer 4 Report

While the introduction provides a thorough overview of the research results published to date, the conclusion is somewhat brief. Considering that the results obtained are partly contradictory and not generalizable, a more extensive discussion of further research objectives would be useful. 

Author Response

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Author Response File: Author Response.docx

Reviewer 5 Report

Before making any recommendations for an interesting scientific article "Investigation on Fracture Performance of Hot Mix Asphalt with Reclaimed Asphalt Pavement under Fatigue Loading", I would like to present the following generally statements on the reviewed article. In order for the article to be could published in the renowned journal Coatings, it needs several improvements. For this purpose, I take the liberty of presenting the following mandatory requirements for inclusion and facultative requirements, the no inclusion of which I require to be credibly justified.

Mandatory requirements:

LNSA (Line Number Scientific Article) 12-24…Abstract…  I would allow myself to take the following position regarding the abstract. In general, I expect from a high-quality scientific abstract a brief global  summary of the solved problem, establishing a scientific hypothesis, an explicit determination of scientific goals and corresponding methodology. In the abstract, a global view is  absent, justification for the choice of 2  presented methods and 2 reference temperatures (-10, +25 C), for the wider scientific community,  clarification of the dissipated energy and the cumulative energy applied to the monitored dependencies. I recommend numerically quantifying "At -10℃, the dissipated energy and the cumulative energy decreased with the increase of RAP content".

LNSA 31-32… Thermal cracking and block cracking belong to the category of cracking caused by environmental factors, such as temperature [1]…it is necessary to specify what environmental temperature the authors have in mind (average air daily or annual temperature, temperature of surface of hot mix asphalt,...). For example, in the scientific article Evaluation of the Effect of Average Annual Temperatures in Slovakia between 1971 and 2020 on Stresses in Rigid Pavements. Land, 11(6), 764, the following research results for Central Europe are presented.   Between 1971 and 2020, an average increase in air annual temperature of 2.1 °C was found, which is 0.7 °C higher than the average increase reported by the Intergovernmental Panel on Climate Change (IPCC). By comparing the authors' research results with the findings of the European Environment Agency from 1976 to 2006, full compatibility of these outputs was identified. For the period 1976 to 2006, the EEA presents an average increase in Ta in Central Europe of 1.2 to 1.5 ° C and the authors found a value of 1.3 ° C in Slovakia.

LNSA 150…3. Materials and Methods... the title of the chapter needs to be moved to the next page.

LNSA 152-153… In this study, two types of binder were used, including SBS modified binder and RAP binder...the abbreviation SBS is not explained in the text of the article.

LNSA 175...Figure 1. Complex modulus... it is desirable to add information about which material the complex modulus refers to. This requirement also applies to Figures 2 and 4.

LNSA 212-213…The fatigue test in this study was a modified version of the displacement-controlled test specified in Tex-248-F,...it would be appropriate to add Tex-248-F into the references.

LNSA 224… Figure 7. Applied load in fatigue loading...it is necessary to add numerical data on the y-axis.

LNSA 304-305…Where Wi is the dissipated energy in cycle i, σi is the stress level in cycle i, εi is the strain level in cycle i, and φi is the phase angle in cycle...it is necessary to indicate physical units  for the individual variables.

LNSA 373-394… 5. Conclusions and recommendation...I recommend omitting recommendation from the title of the chapter, or abstracting the presented findings into explicit recommendations for research and for application practice.

Facultative recommendations:

LNSA 66-67… Stockpiling or burying would occupy land and cause environmental pollution… ."Burying" may not directly cause deterioration of environmental pollution, but it would be a negation of the principles of circular economy in the field of pavement engineering. Pavements should be designed, built, managed, maintained, recycled (decomposed) at a reasonable price, in reasonable quality, respecting the relevant requirements of users, residents and sustainable development. One such minimization measure in the field of pavements may be the sustainable utilization of the reclaimed asphalt pavement (RAP).

LNSA 153-155...RAP binder was ex tracted from RAP using the trichloroethylene. The binder content in RAP was determined to be 4.3%. For all HMAs in this study, the optimum binder content was 6.2%.... Based on what criteria was the optimum binder content of 6.2% determined? I recommend the authors to consider the explanation of the difference between the detected value of 4.3% and the optimal value of 6.2%.

LNSA 172… Table 1. Basic properties of SBS modified binder and RAP binder... I recommend adding into the table or related text the standards according to which the specified characteristics of the binder were determined.

LNSA 189…Figure 4. Aggregate gradation...it would be appropriate to add directly to the title of the picture, for what type HMA are presented aggregate gradation.

LNSA 221-222… Where G is the fracture energy, W is the area underneath the load-displacement curve, Alig is the ligament area of the specimen... I recommend adding physical units to the variables so that dimensional analysis of the equation is possible.

LNSA 376-378… Fatigue life, dissipated energy and cumulative energy were selected to characterize the fatigue resistance of HMA…It is necessary to briefly justify why these characteristics were chosen and to explain the principle of applying dissipated energy to the problem being solved.

As an expert profiled in the field of holistic perception of roadways with an emphasis on circular economy and conservation of non-renewable resources, I rate the article under review as very good in the subject area. After removing the mentioned shortcomings or credible justifications for their non-working, it will be possible to publish a contribution in the renowned scientific magazine Coatings. From the aspect that I have been paying significant attention to the issue of Reclaimed Asphalt Pavement recently, I am able to process a repeated review within 3 working days.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 5 Report

Based on the incorporation of the changes recommended by me, I allow myself to rate the assessed second version of the scientific paper as follows. Reviewed contribution: " Investigation on Fracture Performance of Hot Mix Asphalt with Reclaimed Asphalt Pavement under Fatigue Loading ", I rate it as excellent.  Based on my experience in the assessed issue and subsequent deepening of my knowledge, I am pleased that the submitted 2nd version of the article meets all my essential requirements for a quality scientific article. I am fully satisfied with the implementation of the required changes and recommendations and I hope that I have contributed a little to improving the quality of the assessed scientific contribution.  In conclusion, I would like to sincerely congratulate the authors on a very good scientific article and thank the publisher for the opportunity to expand my scientific knowledge in the following field. Research  of hot mix asphalt durability  with reclaimed asphalt pavement  by fatigue tests using an Overlay Tester using  load-controlled mode.