Induction Heating and Cooling Performance of Asphalt Mixture as Recycling Rap and Steel Slag

Round 1

Reviewer 1 Report

In this paper, the effects of different particle size steel slag and RAP dosage on the induction heating and cooling performance of steel slag recycled asphalt mixtures (SSRAM)were studied, and optimizing the rejuvenator dosage and composition design to investigate the induction heating rate of SSRAM affected by some parameters. The results showed that the 6wt.% of rejuvenator in aged asphalt could evidently restore the physical properties and surface morphology. The study could make a significant reference in promoting solid waste recycling and sustainable asphalt pavement construction. However, there are still some problems that need to be revised before its publication. Thus, a minor revision is necessary, and the specific comments are shown below:

1. The description of the cooling performance of recycled asphalt mixture in the introduction part of this paper is less and should be appropriately supplemented.

2. The description of the experimental process in this paper is relatively simple. The author needs to supplement the pictures of the experiment process.

3. Regarding the relevant conclusions on cooling performance, the cooling rates of steel slag with different particle sizes and RAP content were obtained by different single-factor analyses, but they were obtained under different conditions. What's the connection between them? What is the impact on the overall pavement design?

4. Why should the isovolumetric design method be adopted when the steel slag recycled asphalt mixture specimen is formed in this paper? Can you explain the necessity of using this method?

5. Why does this paper take a reclaimed asphalt mixture of steel slag with 10% RAP as an example? Can you explain?

6. There are some grammatical and syntactic errors in the whole paper. English should be reviewed.

Minor editing of English language required.

Author Response

Reviewer 1#

1. In this paper, the effects of different particle size steel slag and RAP dosage on the induction heating and cooling performance of steel slag recycled asphalt mixtures (SSRAM)were studied, and optimizing the rejuvenator dosage and composition design to investigate the induction heating rate of SSRAM affected by some parameters. The results showed that the 6wt.% of rejuvenator in aged asphalt could evidently restore the physical properties and surface morphology. The study could make a significant reference in promoting solid waste recycling and sustainable asphalt pavement construction. However, there are still some problems that need to be revised before its publication. Thus, a minor revision is necessary, and the specific comments are shown below.

Thanks for your kind comments. We have revised the manuscript according to the provided suggestions, and we have also looked over the expressions of content, whose unprofessional phrases have been polished up by English native. The responses to the comments are showed below. The revised version of manuscript is uploaded, and please check the details by online system then.

2. The description of the cooling performance of recycled asphalt mixture in the introduction part of this paper is less and should be appropriately supplemented.

Thanks for your kind comments. Actually, in the previous studies, the cooling properties are seldom discussed. Instead, the researches toward the induction heating effects were widely studied. So, we have not analyzed the cooling effects by the published literatures. The situation has been explained in the introduction part of revised manuscript, please check the associated revisions from the uploaded file.

3. The description of the experimental process in this paper is relatively simple. The author needs to supplement the pictures of the experiment process.

Thanks for the valued comments. We have supplemented the descriptions for the experiments. You can check the revisions in the uploaded file.

4. Regarding the relevant conclusions on cooling performance, the cooling rates of steel slag with different particle sizes and RAP content were obtained by different single-factor analyses, but they were obtained under different conditions. What's the connection between them? What is the impact on the overall pavement design?

Thanks for your valued comments. Please check the Table 2 in the manuscript. In the experiment, we have designed a control group without the additions of steel slag and RAP. So, for the section of ‘cooling performance’, we would like to analyze the impacts by the different particle sizes of steel slag firstly, then investigated the impacts by different RAP contents. And the results showed that the addition of fine steel slag particles would extend cooling process, while the addition of RAP would shorten the cooling period.

5. Why should the isovolumetric design method be adopted when the steel slag recycled asphalt mixture specimen is formed in this paper? Can you explain the necessity of using this method?

Thanks for the kind comments. The preparation of recycled asphalt mixture specimen is guided by the design specification of recycled asphalt mixture, the Technical specification for asphalt pavement recycling (JTG/T 5521-2019).

6. Why does this paper take a reclaimed asphalt mixture of steel slag with 10% RAP as an example? Can you explain?

Thanks for your kind comments. The RAP addition content of 10% is widely used in the induction heating for recycled asphalt pavement, and we have listed 3 papers below. Of course, Our research group has also conducted the similar experiments with 10% content before. So, we think that 10% RAP addition is a good refence value for the associated experiments.   

Example references:

1. Kumar Pradhan, S.; Das, U.; Ranjan Patra, A., Utilization of reclaimed asphalt pavement (RAP) materials in HMA mixtures for flexible pavement construction. Materials Today: Proceedings 2023.
2. Rout, M. K. D.; Biswas, S.; Shubham, K.; Sinha, A. K., A systematic review on performance of reclaimed asphalt pavement (RAP) as sustainable material in rigid pavement construction: Current status to future perspective. Journal of Building Engineering 2023, 76, 107253.
3. Rahman, M.; Harvey, J.; Buscheck, J.; Brotschi, J.; Mateos, A.; Jones, D.; Pourtahmasb, S., Laboratory performance and construction challenges for plant produced asphalt mixes containing RAP and RAS. Construction and Building Materials 2023, 403, 133082.
4. Jaczewski, M.; Pszczola, M.; Alenowicz, J.; Rys, D.; Dolzycki, B.; Jaskula, P., Evaluation of thermal cracking probability for asphalt concretes with high percentage of RAP. Construction and Building Materials 2023, 400, 132726.
5. There are some grammatical and syntactic errors in the whole paper. English should be reviewed.

Thanks for your valuable comment. We have looked over the manuscript and revised the related expression drawbacks, especially the grammatical and syntactic errors. The language has been polished by English native for a better readability. Please check the revisions by uploaded version.

Reviewer 2 Report

This study aims to investigate the induction heating and cooling performances of asphalt mixture containing RAP and steel slag. Some conclusions were obtained. The following comments are made:

1. The preparation process in Fig. 1 is meaningless. Please redraw to show the flowchart and logic of the process.

2. In section 2.2.4., please give the reasons for the selection of parameters such as “set to 650 V and 7.9 kW”, “ 10-40 mm with an interval of 5 mm”, and “20-100s with an interval of 20s”.

3. In 3.2. , the “Optimization of asphalt aggregate ratio” is the basic process for the preparation of asphalt mixture, it should be removed from the scientific paper here and just show the final ratio of asphalt and aggregate.

4. The conclusions need to be condensed and show the main findings in this paper.

5. The language is pretty poor, it is highly recommended to improve the English expression. For instance, the title, “mixture contained RAP and steel slag”; in the abstract, “This study prepared the steel slag recycled asphalt mixtures (SSRAM) with different particle size steel slag and RAP dosage, and optimizing...”;  “Their properties indexes were listed in Table 1”.

The language is pretty poor, it is highly recommended to improve the English expression

Author Response

Point by point response to reviewers’ comments

Reviewer 1#

1. The preparation process in Fig. 1 is meaningless. Please redraw to show the flowchart and logic of the process.

Thanks for your kind comment. We have deleted the figure 1 and redrawn the figure for the research line. Please check the revised figure in the uploaded file.

2. In section 2.2.4., please give the reasons for the selection of parameters such as “set to 650 V and 7.9 kW”, “10-40 mm with an interval of 5 mm”, and “20-100s with an interval of 20s”.

Thanks for your valuable comment. The similar experimental parameters (but the materials and research objectives are different) have been applied in previous research already, hence, the related parameters in this study have referred to the previous research. We have cited the reference in the revised version. Please check the revisions by uploaded file.

Reference:

Xu, H.; Zou, Y.; Wu, S.; Li, H.; Xu, S.; Zhao, Y.; Lv, Y., Research on gradient characteristics and its prediction method of induction heating asphalt concrete. Construction and Building Materials 2021, 309, 124920.

3. In section 3.2., the “Optimization of asphalt aggregate ratio” is the basic process for the preparation of asphalt mixture, it should be removed from the scientific paper here and just show the final ratio of asphalt and aggregate.

Thanks for your valuable comment. We have deleted the section of “Optimization of asphalt aggregate ratio”, and revised discussion, results and associated conclusion parts. lease check the revisions by uploaded version. 

4. The conclusions need to be condensed and show the main findings in this paper.

Thanks for your valuable comment. we have revised the expressions in the section of the Conclusions, partial revisions are listed below. Please check the revised manuscript by uploaded file.

This study focuses on the induction heating properties of asphalt mixture as adding steel slag and RAP. The rejuvenator dosage and composition design were explored by different heat induced steel slag recycled asphalt mixture. The induced heating rate were employed to analyze the influences by steel fiber dosage, heating time, and heating distance, and the cooling performances were studied under different addition ratios of steel slag and RAP. The significant conclusions were summarized below.  

• The physical properties and surface morphology parameters of aged asphalt can be evidently restored to the level of virgin asphalt, and the optimal dosage of used rejuvenator is 6 wt%.
• The steel fiber in recycled asphalt mixture works as the primary matrix material for induction heating. The heating rate of conventional SSRAM is 0.453 °C/s, while adding 2 wt% of steel fiber in SSRAM could reach 1.204°C/s of heating rate.
• The induced heating rate shows linear positive correlation with heating time and negative exponential relationship with heating distance. The workable interval for induction time and heating distance are 60s-120s and10mm-20mm, respectively.
• Both steel slag aggregate and steel slag filler can reduce the cooling rate of recycled asphalt mixture and enhance the heat storage capacity, which contributes to the healing of cracks during the cooling stage after heating.

5. The language is pretty poor; it is highly recommended to improve the English expression. For instance, the title, “mixture contained RAP and steel slag”; in the abstract, “This study prepared the steel slag recycled asphalt mixtures (SSRAM) with different particle size steel slag and RAP dosage, and optimizing...”, “Their properties indexes were listed in Table 1”.

Thanks for your valuable comment. We have looked over the manuscript and revised the related expression drawbacks (including the mentioned places certainly). The language has been polished by English native for a better readability. Please check the revisions by uploaded version.

Reviewer 3 Report

This manuscript presents a lab study on the heating and cooling performance of asphalt mixtures containing RAP, steel slag, and steel fiber at various dosage combinations. The topic of the study is within the scope of the journal and is innovative. The findings of the study contributed to advancing the field of knowledge in sustainable and green asphalt mixture and asphalt pavements.

The manuscript may be considered for publication after the following comments are addressed:

1.       The manuscript contains a fair amount of grammar errors, inappropriate English writing, and ambiguous sentences. The authors should have carefully proofread or find a professional English editor to proofread the manuscript before submitting the revised version. Below are some examples.

a.       In the title, change “in” to “of”; change “performances” to “performance”; change “contained” to “containing”. You may also consider deleting “Interpretations in”.

b.       Lines 14 and 32, Revise “increasing concerned”

c.       Line 18, plural should follow the word “different”. Change “size” to “sizes” and “dosage” to “dosages”. Make the same changes throughout the manuscript.

d.       Line 20, change “effected” to “affected”.

e.       Line 21, change “by” to “with” or “using”..

f.        Line 25, add a space between “60” and “s”.

g.       Line 37, change “attached” to “gaining”.

h.       Line 38, delete “the”.

i.         Line 47, consider revising “as”

The above are just some examples. There are many other instances in the manuscript that should be revised, clarified, or improved.

2.       The authors only described what had been done in the two references in Lines 50 -54, but did not discuss or comment on the findings from the two studies. Please revise.

3.       Line 110, please provide references to the design specification.

4.       Section 2.2.2 lacks description of specimen compaction procedure (i.e., Marshall compaction).

5.       Figure 1 does not clearly present the preparation procedure of the mixture. The clock times in the top of the figure are confusing. Please revise.

6.       Line 129, I find it difficult to understand “was filled and interfered by the form of gross volume”.

7.       Line 132, should “quality” be “quantity”?

8.       In discussing the 3D morphology results, the authors should introduce how surface roughness of asphalt is related to its performance in asphalt pavement. Otherwise, it is difficult to understand the significance and value of running this test.

9.       Line 265, please revise this sentence as it is currently difficult to understand it.

 

See my previous comments.

Author Response

Point by point response to reviewers’ comments

 

Reviewer 2#

1. This manuscript presents a lab study on the heating and cooling performance of asphalt mixtures containing RAP, steel slag, and steel fiber at various dosage combinations. The topic of the study is within the scope of the journal and is innovative. The findings of the study contributed to advancing the field of knowledge in sustainable and green asphalt mixture and asphalt pavements. The manuscript may be considered for publication after the following comments are addressed.

Thanks for your kind comments. We have modified the manuscript according to your provided suggestions. The revised version shows better readability and research logicality. Please check the revisions by uploaded file then.

2. The manuscript contains a fair amount of grammar errors, inappropriate English writing, and ambiguous sentences. The authors should have carefully proofread or find a professional English editor to proofread the manuscript before submitting the revised version. Below are some examples. In the title, change “in” to “of”; change “performances” to “performance”; change “contained” to “containing”. You may also consider deleting “Interpretations in”. Lines 14 and 32, Revise “increasing concerned”; Line 18, plural should follow the word “different”. Change “size” to “sizes” and “dosage” to “dosages”. Make the same changes throughout the manuscript; Line 20, change “effected” to “affected”; Line 21, change “by” to “with” or “using”; Line 25, add a space between “60” and “s”; Line 37, change “attached” to “gaining”; Line 38, delete “the”; Line 47, consider revising “as”.

Thanks for your valuable comment. We have looked over the manuscript and revised the related expression drawbacks (including the mentioned places certainly). The language has been polished by English native for a better readability. Please check the revisions by uploaded version.  

3. The authors only described what had been done in the two references in Lines 50-54, but did not discuss or comment on the findings from the two studies. Please revise.

Thanks for your kind comments. In the section of Introduction, the mentioned references would like to show that the associated works were widely researched and discussed, so we have not extended their results and findings limited by the space.

4. Line 110, please provide references to the design specification.

Thanks for your valuable comment. We have cited the reference in the revised version.

Reference:

Highway Science Research Institute of the Ministry of Transport, Technical specification for asphalt pavement recycling (JTG/T 5521-2019). In China Communications Press: Beijing, 2019; p 104.

5. Section 2.2.2 lacks description of specimen compaction procedure (i.e., Marshall compaction).

Thanks for your valuable comment. We have supplemented the descriptions for the Marshall compaction in the revised version. Please check the uploaded file then. 

6. Figure 1 does not clearly present the preparation procedure of the mixture. The clock times in the top of the figure are confusing. Please revise.

Thanks for your valuable comment. We have redrawn the Figure 1 for the research flow in the study. Please check it in the revised version.  

7. Line 129, I find it difficult to understand “was filled and interfered by the form of gross volume”.

Thanks for your valuable comment. We have revised the sentence in the newly uploaded version. 

8. Line 132, should “quality” be “quantity”?

Thanks for your valuable comment. We have revised the word in the newly uploaded version.

9. In discussing the 3D morphology results, the authors should introduce how surface roughness of asphalt is related to its performance in asphalt pavement. Otherwise, it is difficult to understand the significance and value of running this test.

Thanks for your valuable comment. We have supplemented the descriptions toward the parameters for 3D morphology test. Several revisions are showed below. Please check the revisions in the uploaded file. 

Afterwards, the surface morphology characteristics of the asphalt samples were analyzed via Multimode Atomic Force Microscope (AFM), which could verify the roughness differences by high precision analysis and calculation, and the arithmetical mean (Ra) and root mean square (Rq) of roughness used as the analysis parameters then. 

10. Line 265, please revise this sentence as it is currently difficult to understand it.

Thanks for your valuable comment. We have revised the sentence in the uploaded file, partial revisions can be seen below. 

Additionally, the surface temperature declines more quickly than the internal position of SSRAM, because the induction heat would vertically transfer to the below areas and surrounding air. Hence, the heat loss of the R1 mixture is faster because the material reveals higher thermal conductivity and thermal diffusivity, which is also the reason why different mixtures exhibit diverse cooling rates. The results from Fig. 11 indicated that the steel slag based aggregate and filler behave certainly thermal conductivity and diffusion coefficient, which could enhance the heat storage capacity of recycled asphalt mixture.

 

Reviewer 4 Report

This manuscript investigates the induction heating and cooling behaviors of steel slag recycled asphalt mixtures. According to the current manuscript, there are some points the authors need to consider for improving the paper, some detailed comments are shown as below:

1. Section 2.1, what is the main chemical compositions of the used rejuvenator?

2. Lines 121-125, it is better to change the label rule, for example, R7 represents a full-component steel slag recycled asphalt mixture, but R10 stands for the steel slag recycled asphalt mixture with 10% RAP, this can easily cause confusion.

3. Lines 124-125, for R0-R40, what kinds of steel slag was added in the recycled mixture? And what is the percentage?

4. Section 2.2.5, what is temperature of the constant temperature chamber?

5. Section 3.1, the dosage of rejuvenator was fixed at 6 wt.% described in section 2.1, then, why did you consider the effect the rejuvenator dosage in section 3.1? I think you need to rearrange the frame.

6. Lines 186-188, the two sentences are basically the same.

7. Please condense Conclusions part for conciseness.

Author Response

Point by point response to reviewers’ comments

Reviewer 3#

1. This manuscript investigates the induction heating and cooling behaviors of steel slag recycled asphalt mixtures. According to the current manuscript, there are some points the authors need to consider for improving the paper. Section 2.1, what is the main chemical compositions of the used rejuvenator?

Thanks for your valuable comment. We have supplemented the description for the used rejuvenator in the revised version. The rejuvenator was obtained from the Jiangsu Subote New Materials Co., Ltd, whose main component was light oil to increase the rheological and fatigue properties [33].

Reference:   

Ye, Q.; Yang, Z.; Lv, S.; Jin, J.; Zhang, S., Study on components selection and performance of bio-oil based asphalt rejuvenator based on softening and asphaltene deagglomeration effect. Journal of Cleaner Production 2023, 419, 138238.  

2. Lines 121-125, it is better to change the label rule, for example, R7 represents a full-component steel slag recycled asphalt mixture, but R10 stands for the steel slag recycled asphalt mixture with 10% RAP, this can easily cause confusion.

Thanks for your valuable comment. We have changed the sample labels in the revised version. The labels of R1 to R7 are used for SSRAM with different particle sizes of steel slag, while Ra to Rd used for the SSRAM with different RAP contents. Please check the revisions in the uploaded file. 

3. Lines 124-125, for R0-R40, what kinds of steel slag was added in the recycled mixture? And what is the percentage?

Thanks for your valuable comment. We have changed the sample labels in the revised version, meanwhile, we supplemented the materials ratios for each group. Partial revisions are listed below. Please check the revisions in the uploaded file. 

To investigated the cooling effects by steel slag aggregate, 7 series of SSRAM samples (labelled with R1 to R7) were prepared by different particle sizes of steel slag aggregate, and another 4 series of SSRAM samples with different dosages of RAP (labelled with Ra to Rd) were produced to investigated the cooling effects by RAP. Meanwhile, the control group of asphalt mixture sample without RAP and steel slag was labelled with R0. The addition content of RAP in R1 to R7 was 30%, and the substitution gradation of steel slag in Ra to Rd were 2.36-16 mm in the SSRAM. The natural aggregate used in the experiment was basalt. The Table 2 listed the specifical additions of steel slag aggregate and RAP for experimental groups.

Table 2 The addition of steel slag aggregate and RAP for experimental groups 

	R0	R1	R2	R3	R4	R5	R6	R7	Ra	Rb	Rc	Rd
Particle size of steel slag (mm)	/	/	9.5-16	4.75-9.5	2.36-4.75	0.075-2.36	0-0.075	0-16	2.36-16	2.36-16	2.36-16	2.36-16
RAP content	/	30%	30%	30%	30%	30%	30%	30%	10%	20%	30%	40%

 

4. Section 2.2.5, what is temperature of the constant temperature chamber?

Thanks for your valuable comment. The temperature of the constant temperature chamber is 80^oC. We have supplemented the description for the parameter in the revised version. Please check the revisions in the uploaded file.  

5. Section 3.1, the dosage of rejuvenator was fixed at 6 wt.% described in section 2.1, then, why did you consider the effect the rejuvenator dosage in section 3.1? I think you need to rearrange the frame.

Thanks for your valuable comment. In the section 2.1, we need to test the basic properties of recycled asphalt, so, we used the 6 wt% of rejuvenator addition as example for the related tests of recycled asphalt. But in the section of 3.1, we need to determine the optimal dosage of rejuvenator, as a result, we conduct the experiments for the asphalt samples with different rejuvenator dosages. To avoid the confusions, we have revised the relevant expressions in the revised version, Please check the revisions in the uploaded file.    

6. Lines 186-188, the two sentences are basically the same.

Thanks for your valuable comment. We have revised the expressions for the mentioned two sentences. Please check the revisions in the uploaded file.

7. Please condense Conclusions part for conciseness.

Thanks for your valuable comment. we have revised the expressions in the section of the Conclusions, partial revisions are listed below. Please check the revised manuscript by uploaded file.

This study focuses on the induction heating properties of asphalt mixture as adding steel slag and RAP. The rejuvenator dosage and composition design were explored by different heat induced steel slag recycled asphalt mixture. The induced heating rate were employed to analyze the influences by steel fiber dosage, heating time, and heating distance, and the cooling performances were studied under different addition ratios of steel slag and RAP. The significant conclusions were summarized below.  

• The physical properties and surface morphology parameters of aged asphalt can be evidently restored to the level of virgin asphalt, and the optimal dosage of used rejuvenator is 6 wt%.
• The steel fiber in recycled asphalt mixture works as the primary matrix material for induction heating. The heating rate of conventional SSRAM is 0.453 °C/s, while adding 2 wt% of steel fiber in SSRAM could reach 1.204°C/s of heating rate.
• The induced heating rate shows linear positive correlation with heating time and negative exponential relationship with heating distance. The workable interval for induction time and heating distance are 60s-120s and10mm-20mm, respectively.

Both steel slag aggregate and steel slag filler can reduce the cooling rate of recycled asphalt mixture and enhance the heat storage capacity, which contributes to the healing of cracks during the cooling stage after heating. 

Round 2

Reviewer 2 Report

The authors have revised the paper according to the comments, it is recommended to accept it after the minor improvement of language.

The language needs to be improved by the native speakers.

Author Response

Reviewer 2#

The authors have revised the paper according to the comments, it is recommended to accept it after the minor improvement of language.

Thanks for your valuable comment. We have looked over the manuscript and revised the related expression drawbacks, especially the grammatical and syntactic errors. The language has been polished by English native for a better readability. Please check the revisions by uploaded version.