A Sustainable Cold Mix Asphalt Mixture Comprising Paper Sludge Ash and Cement Kiln Dust

Round 1

Reviewer 1 Report

The manuscript focuses on improving cold mix asphalt through the utilisation of paper sludge ash and cement kiln dust. In general, the manuscript is well organised and could be considered for publication after a major revision.

Comments and suggestions for the authors:

1.       The Introduction would benefit from a clear structure.

2.       Expression and grammatical mistakes should be corrected, including capitalising the word at the start of a sentence.

3.       Introduction, Page 1. It states that cold mix asphalt lately emerged in the UK. Can the authors specify a specific time?

4.       First paragraph on Page 2. The paragraph misses some detailed references and should be more specific, as the community is not clearly indicated and in which way it contributes to environmental protection.

5.       Second paragraph on Page 2. Though a connect to the previous paragraph is given, why and how substitution is necessary is not provided. This would make it easier to understand the effort for replacing cement in the mixture.

6.       The sentence in line 59 is wrong, as the construction sector is the biggest utilisation sector of waste materials and contributes to high recycling rates in industrial countries. Could the authors be a bit more specific which wastes products they are refereeing to?

7.       Can the authors explain in more detail how cold mix asphalt contributes to environmental sustainability compared to other asphalt mixtures, especially to warm mix asphalt?

8.       The utilisation of waste material in a well investigated field now and to find application for waste materials is a difficulty. Seeing the high amount of waste paper sludge ash and the minor application of cold mix asphalt in the UK, which would insignificantly reduce the waste material. Can the authors elaborate how the application of ash is helpful to the environment?

9.       Materials, Page 3. The physical properties can not confirm a specification properties can be according to specification.

10.   Page 4, Table 2. Can the authors add softening point and needle penetration of the residue? Why were to different binder chosen as reference?

11.   In line 185 and 195, please subscript and superscript the numbers correctly.

12.   Page 7, Figure4. The figure was referenced but not explained, which would be important to the reader. Furthermore, a detailed caption would help to understand the figure better.

13.   Second paragraph, Page 7. Marshall Method for Emulsified Asphalt Aggregate Cold Mixture Design (MS-14), 1989) should be a reference following the reference system used in the manuscript. The same applies for the reference in line 253.

14.   Page 10, Figure 5 and Page 11, Figure 6. The reference binder could be added as lines in the graphic to clearly see when cold mixtures had a similar performance.

15.   Error bars in the figures are missing.

16.   Last paragraph, Page 9. Can the authors provide any references to previous studies to support their explanation?

17.   Does the stiffness increase linear with PSA or CKD, or curation time?

18.   Page 11. Table 6. Standard deviation of the results obtained should be added to the table.

19.   Table 6 and Figure 7. Can the other results of different CKD percentages be added?

20.   Conclusions, Page 13. The first conclusion is incorrect and should be corrected, as mineral filler did not improve the performance compared to waste fly ash.

21.   Point 4 of the conclusion is not a conclusion that can be drawn from this study and is more a suggestion and should be added after the conclusions.

Author Response

We appreciate the applaud from Reviewer #1 in recognising our study’s importance. Moreover, the concerns raised by Reviewer #1 are addressed, and the opportunity accorded for us to improve our manuscript through the invaluable comments is appreciated.

Thank you for your valuable time and advice.

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper introduces a sustainable way for cold mix asphalt mixture by substituting PSA and CKD with conventional aggregate. The research is very meaningful and interesting, whereas there are so many absolute conclusions and spelling mistakes as follows.

1.       The sentence in line 21 is unnecessary, please delete.

2.       Capitalise the first letter of each sentence and remember to write down the punctuation after each sentence. Please check the manuscript throughout.

3.       Make the subtitle for the three figures of Figure 4 clearer.

4.       The combination of CKD and water shows strong alkaline. Does this result affect the bitumen properties, thereby leading to influenced mixture performance?

5.       Which figure is PSA in Figure 8?

6.       For 5^th Conclusion,  could you explain how you get this conclusion as “At 45°C, this mixture forms a cohesive dense microstructure, 400 making it more resistant to rutting.”.

Author Response

We appreciate the precious time spared to critique our manuscript and the opportunity to improve its quality.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors improved the manuscript. Some minor grammar and style issues remained, and some points should be addressed before publication:

1.  The authors should add in the material description that the two binders for HMA are chosen as additional reference, representing traditional binder band for HMA and for performance comparison.

2. Wheel track test results refers to Table 6, which was replaced by a figure.

3. Since this is a research article, it would be great to discuss the other results, which are not shown in the figures. This discussion should include the influence on different substitution rates to the mechanical performances.

Author Response

Thanks for your constructive comments. The manuscript has been revised as requested. 

Author Response File: Author Response.pdf

Reviewer 2 Report

No more comments.

Author Response

Thanks for your constructive comments that highly improved the quality of the paper.