Evaluation of the Influence of Phosphogypsum-Based Composite Filler on Performance of the SMA-13 Asphalt Mixture and Its Harmless Treatment

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

·        Effect of Phosphogypsum in such replacement of limestone mineral filler presents the favor in high temperatures, but in low temperatures, the effect of acidity is very critical and needs more experiments to conclude this parameter.

·        Moisture effect and potential adhesion between aggregates and binder is explained in a very simple form.

The conclusion for detailed analysis in percent of replacement of filler is a way for other research works from the author

Author Response

Reviewer #1: 

• Effect of Phosphogypsum in such replacement of limestone mineral filler presents the favor in high temperatures, but in low temperatures, the effect of acidity is very critical and needs more experiments to conclude this parameter.

Response: Thanks for your comments. We do agree that its acidity will showed a certain impact on mixture’s performance. We are going to investigate the impact of acidity on adhesion at low temperatures in our further research.

• Moisture effect and potential adhesion between aggregates and binder is explained in a very simple form.

Response: Thanks for your comments.The moisture level is crucial for ensuring strong adhesion between aggregates and binder. Too much or too little can weaken the bond.We intend to delve into the study and provide a comprehensive analysis of the moisture effect and the interplay of adhesion between aggregates and binder in further research.

• The conclusion for detailed analysis in percent of replacement of filler is a way for other research works from the author.

Response: Thanks for your comments.We are grateful for your invaluable guidance on shaping our future research direction. We look forward to investigating more deeply into the realm of filler replacement rates in our subsequent studies.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This study tried to develop a environment-friendly phosphogypsum based composite filler (PCF) that can be used as filler of SMA- 13 asphalt mixture. SMA-13 asphalt mixture was firstly designed, following which PCF containing phosphogypsum and steel slag powder was prepared.

Results of this study provided academical support for consumption of phosphogypsum in road engineering effectively and on a large scale.

The article is innovative. It describes the current need. It will advance the scientific view of the issue and I recommend publishing it in a journal.

Author Response

Reviewer #2: 

• This study tried to develop a environment-friendly phosphogypsum based composite filler (PCF) that can be used as filler of SMA- 13 asphalt mixture. SMA-13 asphalt mixture was firstly designed, following which PCF containing phosphogypsum and steel slag powder was prepared.

Response: Thanks for your comments.In line with your suggestion, we have conducted research on an eco-friendly phosphogypsum-based composite filler (PCF), utilizing phosphogypsum as the primary component. We have incorporated this material into SMA-13 asphalt mixtures to evaluate its long-term potential for ion leachate and its impact on pavement performance.

• Results of this study provided academical support for consumption of phosphogypsum in road engineering effectively and on a large scale.

Response: Thanks for your comments.

• The article is innovative. It describes the current need. It will advance the scientific view of the issue and I recommend publishing it in a journal.

 Response: Thanks for your comments.We are deeply grateful for your support and are eager to see our research make a meaningful impact in addressing the pressing issue of phosphogypsum waste disposal.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

A very interesting Article on the possibility of using phosphogypsum as a filler of SMA-13. However, the article looks messy and needs some corrections.

There is no reference in the text for Fig. 2 and Fig. 4. Section 2.2 should contain a reference to Fig. 3, not Fig. 1. Starting with Chapter 3, the references to all figures are incorrect. The numbering of the tables is incorrect: Table 3 comes first, then Table 5, and then Table 4. It is necessary to check all the numbering and references to tables and figures throughout the article.

What ratio of phosphogypsum and steel slag powder was used to prepare PCF? This information should be presented at the beginning of the article.

All norms and standards with their full titles should be included in the reference list. If they are in Chinese, provide an English transcription.

In Section 3.1, the Chinese script should be replaced with an English transcription.

In many countries, the EPA Regulations (Environmental Protection Agency)  prohibit the use of phosphogypsum in asphalt pavement.  What do the authors think about this? Is there any possibility of using the proposed composite in practice?

The authors claim a positive effect of phosphogypsum on the parameters studied. However, it is not known for certain whether it is phosphogypsum that has a positive effect, or is it the effect of steel slag powder? Perhaps the positive effect is caused only by the steel slag powder contained in the composite. SEM images and microstructure analysis could provide answers to this.

Author Response

Reviewer #3: 

• A very interesting Article on the possibility of using phosphogypsum as a filler of SMA-13. However, the article looks messy and needs some corrections.

Response: Thanks for your comments. The manuscript has been carefully revised according to your comments.

• There is no reference in the text for Fig. 2 and Fig. 4. Section 2.2 should contain a reference to Fig. 3, not Fig. 1. Starting with Chapter 3, the references to all figures are incorrect. The numbering of the tables is incorrect: Table 3 comes first, then Table 5, and then Table 4. It is necessary to check all the numbering and references to tables and figures throughout the article.

Response: Thanks for your comments. Formatting issues with the images and tables in our articles have been addressed by adjusting the layout of all tables and images to ensure clarity and readability throughout the articles.

• What ratio of phosphogypsum and steel slag powder was used to prepare PCF? This information should be presented at the beginning of the article.

Response: Thanks for your comments. Optimal ratio of phosphogypsum to steel slag powder used in the PCF was 65% to 35%. This information has been included in the article for clarity.

• All norms and standards with their full titles should be included in the reference list. If they are in Chinese, provide an English transcription.

Response: Thanks for your comments.We revised the content of the article according to your suggestions.

• In Section 3.1, the Chinese script should be replaced with an English transcription.

Response: Thanks for your comments. The Chinese content has been updated with the correct English translations accordingly.

• In many countries, the EPA Regulations (Environmental Protection Agency)  prohibit the use of phosphogypsum in asphalt pavement.  What do the authors think about this? Is there any possibility of using the proposed composite in practice?

Response:Thanks for your comments. EPA regulations prohibit the use of phosphogypsum in asphalt pavements because the long-term hazardous ionic spillage of phosphogypsum is uncontrollable. In this study, the long-term hazardous ionic spillage of steel slag blended to form PCF can be significantly suppressed. It proved that the PCF blended with steel slag has a great potential to be used in road projects .

• The authors claim a positive effect of phosphogypsum on the parameters studied. However, it is not known for certain whether it is phosphogypsum that has a positive effect, or is it the effect of steel slag powder? Perhaps the positive effect is caused only by the steel slag powder contained in the composite. SEM images and microstructure analysis could provide answers to this.

Response: Thanks for your comments. Both phosphogypsum and steel slag powder were solid waste. Our study introduces steel slag as a modifier to neutralize the acidity of phosphogypsum, thereby minimizing the risks associated with prolonged hazardous ion leaching. The combined use of steel slag and phosphogypsum to create a PCF has yielded positive effects on the study’s parameters. Moving forward, we plan to employ SEM and microstructural analysis to refine our findings. We are grateful for your guidance on the direction of our future research.

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

Thank You for providing answers to my questions. I’m satisfied and agreed with that.