Freeze and Thaw Effect on Asphalt Concrete Mixtures Modified with Natural Bentonite Clay
Round 1
Reviewer 1 Report
Thank you for inviting me to evaluate the manuscript title “Freezing and Thawing Effect on Asphalt Concrete Mixtures Modified with Natural Bentonite Clay”. In this manuscript, the authors used natural bentonite clay to improve the performance of concrete mixture. In my opinion, the research objective is clear. The content structure is basically reasonable. And the experimental results are seemingly acceptable which can support the feasibility of the methods.
However, there are several points which should be addressed to improve the quality of the paper.
1. In abstract, please use the correct tense and reduce the use of complicated and difficult sentence patterns. It is suggested to revise the grammar and presentation questions in the whole manuscript.
2.The presentation of some of the images, tables and formulae in the text needs to be fine-tuned to make them clearer.
3.There are errors in the format of references, e.g. 5, 6, 11, please double check.
4.The optimum amount of bentonite in the text may also be 7%. Does the recommended amount of bentonite vary considerably for different types of asphalt concrete? Several additional sets of data could be considered.
5.What is the effect of adding bentonite on the other road properties of the asphalt mix?
6.Researchers have already published studies almost identical to this article, and it is important to highlight the innovative nature of this article.
It is recommended that the manuscript be accepted with major revisions.
Author Response
Thank you very much for your great work, your comments are very valuable and contributed well to improve our manuscript. Please find below our responses to the comments which are reflected in the manuscript and highlighted in yellow:
1. In abstract, please use the correct tense and reduce the use of complicated and difficult sentence patterns. It is suggested to revise the grammar and presentation questions in the whole manuscript.
The abstract was improved. Tenses were corrected and difficult sentences were improved to become easy to read. All grammar and presentation in the whole manuscript were revised.
2.The presentation of some of the images, tables and formulae in the text needs to be fine-tuned to make them clearer.
The presentation of the figures, images, tables, and formulae were fine-tuned as recommended.
3.There are errors in the format of references, e.g. 5, 6, 11, please double check.
All errors in the format of references were checked and corrected.
4.The optimum amount of bentonite in the text may also be 7%. Does the recommended amount of bentonite vary considerably for different types of asphalt concrete? Several additional sets of data could be considered.
Thank you for the important note, the problem with Adding more than 5% such as 7% bentonite content leads to increase the weight loss of AC after rapid FT cycles for 8 continuous weeks to reach up to 4.5% compared with 2.3% weight loss for 5% bentonite content as illustrated by Figure 5. That’s why the chosen optimum bentonite content was selected to be 5%. This piece of information has been added to the discussion and conclusion parts in the revised manuscript.
5.What is the effect of adding bentonite on the other road properties of the asphalt mix?
To respond to this comment, the authors decided to add more figures attained from the lab tests to the main manuscript that answer the respected reviewer question which include the effect of bentonite percentage on AC mix density, air void, V.M.A, and V.F.A., these results are also discussed in the discussion part and highlighted in yellow color.
6.Researchers have already published studies almost identical to this article, and it is important to highlight the innovative nature of this article.
The authors highlighted the innovative nature of this article in the abstract in the revised manuscript. This article is focused on the effect of FT cycles on AC mixtures, and the benefit of NBC partial replacement of mineral filler aggregate to reduce the damage occurs to the pavement due to FT cycles, which has never been studied nor published before.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Freezing and Thawing Effect on Asphalt Concrete Mixtures Modified with Natural Bentonite Clay
This study aimed to explore the effect of freezing and thawing (FT) cycles on the perfor-mance of asphalt concrete mixtures (AC) modified by partially replacing the mineral filler fraction of aggregates by natural bentonite clay (NBC). AC mixtures after being exposed to FT cycles lose their stability and become lower than the minimum requirements which will lead to faster damage of pavements. In order to enhance the AC mixtures abilities to sustain severe FT cycles this study.
I have read the paper with interest.
The manuscript topic is of interest for “Stability of asphalt concrete mixture”.
The authors offer a work that potentially can improve our knowledge about the topic of interest. I suggest that the authors consider a revision of their work along the following suggestions and questions.
Suggestions and Questions:
1-The selected experimental object is the characteristics of medium density limestone crushed stone aggregate from Jordan. It is suggested that the author briefly describe the reasons.
2-How much natural bentonite can be added to asphalt concrete mixture to effectively reduce expansion, the author is suggested to briefly describe.
3-It is suggested to add more pictures and flow charts to demonstrate the experimental process, so that readers can understand it more intuitively.
4-What are the advantages and disadvantages of this study? I suggest that the author emphasize this topic.
5-It is suggested that the author explain the engineering application and future prospects in more detail.
6-The abstract of the article needs to be revised, and the importance of the article should be highlighted. There are insufficient references, so more references need to be supplemented. There are too few references, which need to be supplemented to 30. The background and mechanism are not introduced clearly.
Siddique, R., & Singh, G. (2011). Utilization of waste foundry sand (WFS) in concrete manufacturing. Resources, Conservation and Recycling, 55(11), 885-892.
Xue Y., Ranjith P.G., Chen Y., Cai C., Gao F., Liu X. (2023). Nonlinear mechanical characteristics and damage constitutive model of coal under CO2 adsorption during geological sequestration. Fuel, 331, 125690.
Author Response
Dear Reviewer,
Thank you very much for your great work, your comments are valuable and contributed to improve the quality of our work. Please find below our responses to your comments which are reflected in the manuscript and highlighted in yellow in the revised version.
1-The selected experimental object is the characteristics of medium density limestone crushed stone aggregate from Jordan. It is suggested that the author briefly describe the reasons.
The reason is that this type of crushed limestone aggregate is widely abundant in Jordan with reasonable cost for road construction. Our answer for this suggestion is reflected and highlighted in the revised manuscript.
2-How much natural bentonite can be added to asphalt concrete mixture to effectively reduce expansion, the author is suggested to briefly describe.
5% NBC replacement of the mineral filler which is very low amount as the mineral filler forms only 55 g out of 1100 g of the total aggregate, that means the substitution is 0.05*55=2.75 g of NBC and 52.25 g of mineral filler to be added to 770 g of course aggregate, and 275 of fine aggregate. This amount of NBC (0.25% of total aggregate) is very low and will not cause the expansion of AC mix specially that the amount of NBC is low, hence their particles will be coated by the binder material (bitumen) and eliminate their swelling capacity. The addition of more than 5% NBC will increase the possibility of weight loss of AC pavement after continuous 8 weeks of rapid FT cycles. For example, by adding 7% of bentonite the weight loss reaches up to 4.5% compared with 2.3% weight loss for 5% bentonite content as illustrated by Figure 5. That’s why the chosen optimum bentonite content was selected to be 5%. This answer is reflected and highlighted in the revised manuscript.
The stability of modified mixtures decreased with increasing bentonite clay content over 15%, which is also consistent with the trend of density (Figure 3.a) and V.F.A (Figure 3.d) for modified AC mixtures, with lowest air voids and V.M.A (Figures 3.b and 3.c) and which might be a result of reduction in adhesion of bitumen to aggregates and separation of the aggregates in the specimen.
3-It is suggested to add more pictures and flow charts to demonstrate the experimental process, so that readers can understand it more intuitively.
Yes, based on this comment, the authors decided to add 4 more charts. Figure 3. Bentonite variation with: a. density, b. air void, c. V.M.A, d. V.F.A, e. original and retained stability. Moreover, highlighted discussion is added to the revised manuscript as well.
4-What are the advantages and disadvantages of this study? I suggest that the author emphasize this topic.
This research work proves that Adding 5% of NBC in asphalt concrete mixtures in the form of partial replacement of mineral filler in the aggregate satisfies the asphalt mixture requirements for medium traffic conditions and reduces the damage caused by continuous 8 weeks of rapid freezing and thawing cycles by 13% compared to control/unmodified specimens. Additionally, it provides the smallest amount of AC weight loss after rapid FT cycles. The natural bentonite clay is widely available and inexpensive which leads to extending the pavement life and reducing the maintenance cost. This is well reflected in the revised manuscript.
5-It is suggested that the author explain the engineering application and future prospects in more detail.
The proposed improved AC mixture can be applied in the future in cold region areas that suffer from the consequences of FT cycles on pavements, and contributes in reducing the pavements damage, hence prolong their service life. This paragraph is added to the revised manuscript in the conclusion part.
6-The abstract of the article needs to be revised, and the importance of the article should be highlighted. There are insufficient references, so more references need to be supplemented. There are too few references, which need to be supplemented to 30. The background and mechanism are not introduced clearly.
The abstract is revised and the importance of the article is highlighted. More references are added to the revised manuscript including the suggested references by the respected reviewer.
Siddique, R., & Singh, G. (2011). Utilization of waste foundry sand (WFS) in concrete manufacturing. Resources, Conservation and Recycling, 55(11), 885-892.
Xue Y., Ranjith P.G., Chen Y., Cai C., Gao F., Liu X. (2023). Nonlinear mechanical characteristics and damage constitutive model of coal under CO2 adsorption during geological sequestration. Fuel, 331, 125690.
Author Response File: Author Response.docx
Reviewer 3 Report
The manuscript entitled "Freezing and Thawing Effect on Asphalt Concrete Mixtures Modified with Natural Bentonite Clay" provides an in-depth discussion of the effects of freezing and thawing (FT) cycles on the performance of asphalt concrete mixtures (AC) modified by partially replacing the mineral filler fraction of aggregates by natural bentonite clay (NBC). However, the manuscript has a few shortcomings, which should be address before considering publication.
1. The literature review needs to be concise and clearly define how the paper address the gap in literature considering that lots of work conducted on asphalt concrete. Describe how the objectives are unique from the previous studies that conducted similar work on mechanical behavior of asphalt mixes. Due to that, relevant study suggest to cited, as follow:
*Xuan Zhu, Guoping Qian, Huanan Yu, et al., Evaluation of coarse aggregate movement and contact unbalanced force during asphalt mixture compaction process based on discrete element method, Construction and Building Materials. 328 (2022) 127004. https://doi.org/10.1016/j.conbuildmat.2022.127004.
*Guihai Nie, Xu Cai, Wenke Huang, et al., Designing of an anti-rutting and High Ductility Asphalt Mixture based on mortar performance, Construction and Building Materials. 316 (2022) 125837. https://doi.org/10.1016/j.conbuildmat.2021.125837
*Hui Wei, Jue Li, Feiyue Wang, et al., Numerical investigation on fracture evolution of asphalt mixture compared with acoustic emission, International Journal of Pavement Engineering. 23(10) (2022) 3481–3491. https://doi.org/10.1080/10298436.2021.1902524.
2. The word “at 25” in line 112 expresses repetition.
3. In the ultrasonic pulse velocity (UPV) measurement, it is suggested to establish a relationship between the influence of bentonite content on the average velocity and damage index, and conduct a comprehensive analysis.
4. In the full text, Marshall test and ultrasonic pulse velocity (UPV) measurement are respectively used to evaluate the impact of freeze-thaw cycle on asphalt mixture performance. The two methods are relatively independent, and the relationship between the characterization indexes of the two tests can be considered to establish more comprehensive consideration of the improvement of bentonite on asphalt mixture performance.
5. The content of bentonite has a significant impact on the performance of asphalt mixture under freeze-thaw cycle. The author is not clear enough in the explanation process, so it is suggested to supplement the analysis of the impact of bentonite on the rheological properties of asphalt mortar.
6. The format of references needs to be unified.
7. The second and third conclusions are concise.
Author Response
Dear respected Reviewer,
In fact, your comments were excellent, they contributed very well in improving our work. We added new work as per your request which really makes the manuscript more professional and higher quality. We really thank you for your great work and suggestions. Please find below our responses to your valuable comments which are reflected in the revised manuscript and highlighted in green color.
The literature review needs to be concise and clearly define how the paper address the gap in literature considering that lots of work conducted on asphalt concrete. Describe how the objectives are unique from the previous studies that conducted similar work on mechanical behavior of asphalt mixes. Due to that, relevant study suggest to cited, as follow:
*Xuan Zhu, Guoping Qian, Huanan Yu, et al., Evaluation of coarse aggregate movement and contact unbalanced force during asphalt mixture compaction process based on discrete element method, Construction and Building Materials. 328 (2022) 127004. https://doi.org/10.1016/j.conbuildmat.2022.127004.
*Guihai Nie, Xu Cai, Wenke Huang, et al., Designing of an anti-rutting and High Ductility Asphalt Mixture based on mortar performance, Construction and Building Materials. 316 (2022) 125837. https://doi.org/10.1016/j.conbuildmat.2021.125837
*Hui Wei, Jue Li, Feiyue Wang, et al., Numerical investigation on fracture evolution of asphalt mixture compared with acoustic emission, International Journal of Pavement Engineering. 23(10) (2022) 3481–3491. https://doi.org/10.1080/10298436.2021.1902524.
The following references were added which fill the gap in the literature and a paragraph shown below was added to address how the objectives of this study are unique from the previous studies that conducted similar work on mechanical behavior of asphalt mixes:
*Xuan Zhu, Guoping Qian, Huanan Yu, Evaluation of coarse aggregate movement and contact unbalanced force during asphalt mixture compaction process based on discrete element method, Construction and Building Materials. 328 (2022) 127004. https://doi.org/10.1016/j.conbuildmat.2022.127004.
*Guihai Nie, Xu Cai, Wenke Huang, et al., Designing of an anti-rutting and High Ductility Asphalt Mixture based on mortar performance, Construction and Building Materials. 316 (2022) 125837. https://doi.org/10.1016/j.conbuildmat.2021.125837
*Hui Wei, Jue Li, Feiyue Wang, et al., Numerical investigation on fracture evolution of asphalt mixture compared with acoustic emission, International Journal of Pavement Engineering. 23(10) (2022) 3481–3491. https://doi.org/10.1080/10298436.2021.1902524.
Siddique, R., & Singh, G. (2011). Utilization of waste foundry sand (WFS) in concrete manufacturing. Resources, Conservation and Recycling, 55(11), 885-892.
Xue Y., Ranjith P.G., Chen Y., Cai C., Gao F., Liu X. (2023). Nonlinear mechanical characteristics and damage constitutive model of coal under CO2 adsorption during geological sequestration. Fuel, 331, 125690.
The incorporation of this abundantly available and economically affordable NBC in asphalt concrete could lead to both sustainable pavement construction and environment preservation. It is, therefore, needed to expand existing research on asphalt and asphalt concrete modification to inspect the effect asphalt modification with NBC on physical, rheological and mechanical properties of asphalt pavements especially under freezing and thawing conditions.
- The word “at 25” in line 112 expresses repetition.
Repetition is removed.
- In the ultrasonic pulse velocity (UPV) measurement, it is suggested to establish a relationship between the influence of bentonite content on the average velocity and damage index, and conduct a comprehensive analysis.
Very good suggestion!
To establish a relationship between the influence of bentonite content on the average velocity and damage index, a comprehensive analysis was conducted. Linear relationships were established between average velocity and damage index versus the number of weeks specimens are subjected to FT cycles at different bentonite contents. The coefficient of determination (R2) was used to access the goodness of linear fit. R2 is known as a numerical value that implies the amount of variance explained by the independent variable(s) in the model. This coefficient of determination is calculated by the following equation:
where R2 = regression model fitting parameter, SSR = sum of squares of errors (residuals), SST = total sum of squares around the mean, Yi = actual dependent variable acquired from experimental work, Yp = predicted dependent variable obtained from the regression model, and Yavg = average value of the actual dependent variable acquired from the experimental study. The developed linear models between average velocity and number of FT weeks and damage index versus number of FT weeks at different bentonite contents along with their respective R2 values are tabulated in Tables 4 and 5, respectively. Based on the developed models it can be seen that the established linear models very well explained the variation in the dependent variables (average velocity and damage index) at 95% or better. In addition, it was observed analytically that bentonite content played a significant role in asphalt mixtures performance under different periods of freezing and thawing.
Table 4: developed linear models between average velocity and number of FT weeks
|
Bentonite Content (%) |
Linear Model (Y = Average Velocity & X = number of FT weeks) |
R2 (%) |
|
0 |
y = -0.1011x + 3.2028 |
95.87 |
|
5 |
y = -0.1006x + 3.4438 |
99.60 |
|
10 |
y = -0.1268x + 3.1535 |
97.40 |
|
15 |
y = -0.1082x + 3.0239 |
98.94 |
|
20 |
y = -0.1038x + 3.362 |
97.33 |
Table 5: developed linear models between damage index and number of FT weeks
|
Bentonite Content (%) |
Linear Model (y = Damage Index & x = number of FT weeks) |
R2 (%) |
|
0 |
y = 0.0527x + 0.0403 |
95.65 |
|
5 |
y = 0.0498x + 0.0364 |
99.63 |
|
10 |
y = 0.0588x + 0.1166 |
96.76 |
|
15 |
y = 0.063x + 0.0072 |
98.87 |
|
20 |
y = 0.0555x + 0.0045 |
96.42 |
- In the full text, Marshall test and ultrasonic pulse velocity (UPV) measurement are respectively used to evaluate the impact of freeze-thaw cycle on asphalt mixture performance. The two methods are relatively independent, and the relationship between the characterization indexes of the two tests can be considered to establish more comprehensive consideration of the improvement of bentonite on asphalt mixture performance.
Another very good suggestion!
Marshall test and ultrasonic pulse velocity (UPV) measurements are respectively used to evaluate the impact of freeze-thaw cycles on asphalt mixture performance. The two methods are relatively independent, and the relationship between the characterization indexes of the two tests was considered to establish more comprehensive consideration of the improvement of bentonite on asphalt mixture performance. To that end, the single factor analysis of Variance (ANOVA) was carried out where bentonite content was used as the factor based on which comparison was conducted versus flow, stability, average velocity and damage index at 0 weeks of FT cycles and flow, stability, average velocity and damage index after 8 weeks of continuous FT cycles. Results are presented in Tables 6, 7; where Table 6 presents the descriptive statistics for the variables used in the ANOVA analysis and Table 7 shows the single factor ANOVA analysis results. It can be statistically seen, as was graphically proven, that the bentonite content is significantly, on the 0.05 significance level, affecting all tests indexes, which supports the motivation of this research work. It is of great importance to point out that the p-value came out to be < 0.0001, which implies the high influencing effect bentonite has on asphalt mixtures behavior under freeze-thaw cycles. This in turn indicates that modifying asphalt concrete with natural bentonite clay could help in mixtures weathering resistance with repeated cycles of freezing and thawing in addition to wetting and drying.
Table 6. single factor ANOVA analysis results
|
Groups |
Count |
Sum |
Average |
Variance |
|
Bentonite Content (%) |
40 |
400 |
10 |
51.28205 |
|
Tests Indexes |
40 |
151.8697 |
3.796742 |
9.352331 |
Table 7. single factor ANOVA analysis results
|
Source of Variation |
SS |
df |
MS |
F |
P-value |
F crit |
|
Between Groups |
769.61 |
1 |
769.61 |
25.39 |
2.96E-06 |
3.96 |
|
Within Groups |
2364.74 |
78 |
30.32 |
|||
|
Total |
3134.35 |
79 |
|
|
|
|
- The content of bentonite has a significant impact on the performance of asphalt mixture under freeze-thaw cycle. The author is not clear enough in the explanation process, so it is suggested to supplement the analysis of the impact of bentonite on the rheological properties of asphalt mortar.
Please refer to responses on comments 3 and 4. Furthermore, it is not quite straight forward to address the significant effect bentonite has on the performance of asphalt mixtures under freeze-thaw cycles as it helps in some aspects and does not do quite as well or negatively impact other aspects. However, as was experimentally proven, under all circumstances performance always meets design specifications.
- The format of references needs to be unified.
The references in the revised manuscript are unified as per your request.
- The second and third conclusions are concise.
Thank you very much.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The paper has been improved to a certain extent after the author's revision, but there are still some problems:
The optimum bentonite dose recommended in the manuscript is 5%. Will the recommended bentonite dose vary considerably for different types of asphalt concrete? Will the addition of bentonite improve other road properties?
Author Response
Thank you very much for your time and effort you put in evaluating our work. In fact, these are two legitimate comments that could be used to open research line in this area to investigate the effect of changing the asphalt concrete job mix formulas and how it affects the optimum bentonite dosage. Also, bentonite incorporation into asphalt concrete will definitely alter rutting and cracking resistance which is something that could be studied in a future research effort.
Again we thank you very much for your valuable comments.
Authors
On their behalf
Dr. Mousa Bani Baker
Please find attached the revised manuscript
Author Response File: Author Response.docx
Reviewer 2 Report
accept
Author Response
Thank you very much for your time and effort in evaluating our work.
The revised manuscript has been improved and spelled checked properly.
Please find attached the revised manuscript.
Kind regards,
Authors
Author Response File: Author Response.docx
