Improving the Mechanical Properties and Durability of Cold Bitumen Emulsion Mixtures Using Waste Products and Microwave Heating Energy

Response to Editor’s and other general comments

General comment:

Your manuscript has now been reviewed by experts in the field. Please revise the manuscript according to the referees' comments and upload  the revised file within 7 days.

The authors wish to commend the reviewers’ diligent work on the manuscript. Moreover, we reiterated our willingness to revise the manuscript by affecting all the editor and reviewers’ observations and corrections and resubmitting within the stipulated time frame. We are glad that our manuscript is found worthy of publication.

Respond to comments (reviewer #1)

Comments/Remarks

Response

General:

In the present paper authors have experimentally investigated the method for controlling air voids within pavement specifications without affecting mechanical behavior by using waste paper sludge ash(PSA) as a filler in CBEM instead of the conventional mineral filler(CMF) and highlighted the change by reducing the amount of CBEM air voids using micro- wave (MW) heating energy as a post-treatment method. The paper requires some improvement, especially in technical contents. Since the laboratory results are nevertheless interesting, it is proposed to re-submit a thoroughly revised version of the manuscript, considering the following comments.

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

1.     Overall recommendation should be reported in one sentence at the end of the abstract

Thank you for your comment.

The amendment has been done according to the reviewer comments.

The following sentence has been added:

“The findings point to the need to adopt CBEM post-heating approaches, particularly the MW treatment procedure”.

2.     Experimental work: Probably the most useful contribution of the authors is the experimental data, the authors are invited to improve the section of the experimental program by introducing further information and pictures about experimental testing program.

Thank you for your comment.

The amendment has been done according to the reviewer comments.

3.     Emphasizing the importance of research in introduction

Thank you for your comment.

The amendment has been done according to the reviewer comments.

This sentence has been added:

“Finally, the development and enhancement of asphalt mixtures to associate with the global context of sustainable materials production at low cost are highlighted in this research work as a main aim. Using waste materials with the capability of low power technique (microwave processing) to improve asphalt mixtures, is the main hypothesis to sustain the aim

4.     The presented test results in discussion part can be compared with other test results available in literature.

Thank you for your comment.

The amendment has been done according to the reviewer comments.

5.     The paper is well written and it is easy to follow, only the authors needs to go thoroughly revised version to correct the typo-mistake.

Thank you for your comment.

The amendment has been done according to the reviewer comments.

A native English proofreader has revised the manuscript.

In addition, the manuscript is checked for grammatical errors using Grammarly software. All typographical errors are now reduced to the publishing nearest minimum, as humanly possible.

6.     Author should highlight the assumptions and limitations and future research direction of the study.

Thank you for your comment.

The amendment has been done according to the reviewer comments.

The assumptions and limitations and future research direction of the study have been highlighted.

This sentence has been added:

“However, many limitations need to be mentioned in this research work, such as, the study was conducted with a non-industrial scale microwave, the lab process could be different on field application, and specific material is used (different material have different response to microwave processing), etc.. these points and more need to be covered in details for more understanding the benefits of microwave processing technique. Nevertheless, this attempt is a part of the required efforts to disclose the potential of the microwave technique. Therefore, the following sections try to disclose the experiment program to achieve such an aim.”

Response to Editor’s and other general comments

General comment:

Your manuscript has now been reviewed by experts in the field. Please revise the manuscript according to the referees' comments and upload  the revised file within 7 days.

The authors wish to commend the reviewers’ diligent work on the manuscript. Moreover, we reiterated our willingness to revise the manuscript by affecting all the editor and reviewers’ observations and corrections and resubmitting within the stipulated time frame. We are glad that our manuscript is found worthy of publication.

Respond to comments (reviewer #2)

Comments/Remarks

Response

General:

The authors did a good job using waste products and microwave heating energy to improve the mechanical properties and durability of cold bitumen emulsion mixtures; This scope needs such studies. However, in order to raise the quality of the manuscript to bring it to the required level in the journal “Buildings”, the reviewer recommends deep processing of the comments.

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

1.      Is it feasible to subject the mixture to microwave irradiation heating rather than conventional techniques for large scale production?

Many thanks for rising a vital point to the discussion, which is the applicability of implementing any technique from the lab scale to the industrial scale. the authors did an extensive survey on such an interesting issue, the following paragraph is added to address this point:

“Since the 1970s, microwave heating has been applied to processing for pavement maintenance in the USA [45].

The use of microwaves in field asphalt technology will inevitably present some challenges, but these will be resolved via continued research, testing, and improvement.”

2.      Why the authors have chosen limestone, PSA as fillers. There are various other fillers such as glass powder, red mud, stone dust, marble dust, etc. There are numerous studies on the suitability of above-mentioned fillers. Please elaborate and include the importance of selected fillers in the manuscript

Thank you for your comment.

More information has been added as per the reviewer comment to support this statement.

“Limestone filler is widely used as a commercial filler in both HMA and CMA. PSA is generated from power plants that burn waste at temperatures between 850 ºC and 1100 ºC by the use of a fluidized bed combustion technology. It is a promising sustainable material to use as a filler in bituminous mixes since it has a chemical structure similar to ordinary Portland cement (OPC), consisting of silica, calcium oxide, and alumina [36,37].”

3.      Authors have not shown the value of ITSM for HMA at different curing days

Thank you for your comment.

It is worth mentioning that HMA gains its mature strength directly after the mix cools down after laying, therefore single read normally represents HMA strength, while cold mix asphalt needs a long time due to trapped water on one side and the hydration process if the hydraulic or cementitious filler is any in the mix

4.      the decision on heating time is a big challenge. How the authors have decided microwave heating time. Why the authors terminated at 10 minutes. Have the authors tried to check for longer times?

Thank you for your comment.

The authors terminated the microwave heating at 10 minutes as the mix temperature rise quickly above 101 ⁰C, accordingly the extra heating led to evaporation the trapped water in the mix which is necessary to sustain the hydration process. In other words, the amount of water removed during the heating process should be maximized to avoid removing any that is needed for hydration.

5.      decrease in viscosity always decreases the air voids?

Thank you for your comment.

If the reviewer means the other factors such as aggregate type, angularity, binder type, filler type and content, etc, these factors were been constant in this study, therefore, the main remaining factors are Air voids in the samples are reduced due to the decrease in base bitumen viscosity, while workability is enhanced due to the increase in the mix temperature and the loss of trapped water.

6.      There are several other factors affecting air voids. Please add reference and provide proper justification.

Thank you for your comment.

Other reasons have been added as per the reviewer comment.

“While workability is improved due to a rise in mix temperature and the release of trapped water, air voids in the samples are reduced due to a decrease in base bitumen viscosity.”

7.      How was the micro-wave process conducted? Any figure to show the operation?

Thank you for your comment.

Sub-section 2.2. Mix design and sample preparations. Figure 1 shows the microwave process.

8.      was the reduction in air voids caused by the micro-wave operation or the addition of PSA?

Thank you for your comment.

Both microwave operation and the addition of PSA caused a reduction in air voids.

9.      Did micro-wave heating accelerate the hydration and help improve the pore structure and mechanical strength?

Thank you for your comment.

It is worth mentioning that the air voids decreased from 7.51% to 4.99% when replacing the limestone with PSA (at 90 C). Pore size and its continuity are vital factors regarding the evaluation of the mechanical and durability properties of the mix. Noticeably, the progression of hydration products due to the existence of PSA is facilitated by blocking or minimizing pore size and/or their continuity, thus preventing the free movement of attached water and air. In consequence, blocking also produces a solid structure, which possesses higher strength and durability.

Response to Editor’s and other general comments

General comment:

Your manuscript has now been reviewed by experts in the field. Please revise the manuscript according to the referees' comments and upload  the revised file within 7 days.

The authors wish to commend the reviewers’ diligent work on the manuscript. Moreover, we reiterated our willingness to revise the manuscript by affecting all the editor and reviewers’ observations and corrections and resubmitting within the stipulated time frame. We are glad that our manuscript is found worthy of publication.

Respond to comments (reviewer #3)

Comments/Remarks

Response

General:

This work investigated the application paper sludge ash and microwave heating in the cold mix asphalt, and some specific comments could be seen below:

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

1) Page 4, Line 156: The “former” should be revised to “latter”.

Thank you for your comment.

The amendment has been done according to the reviewer comments.

2) At the end of the Introduction section, the motivation and main objectives of this study should be summarized.

Thank you for your comment.

The amendment has been done according to the reviewer comments.

This sentence has been added:

“Finally, the development and enhancement of asphalt mixtures to associate with the global context of sustainable materials production at low cost are highlighted in this research work as a main aim. Using waste materials with the capability of low power technique (microwave processing) to improve asphalt mixtures, is the main hypothesis to sustain the aim. However, many limitations need to be mentioned in this research work, such as, the study was conducted with a non-industrial scale microwave, the lab process could be different on field application, and specific material is used (different material have different response to microwave processing), etc.. these points and more need to be covered in details for more understanding the benefits of microwave processing technique. Nevertheless, this attempt is a part of the required efforts to disclose the potential of the microwave technique. Therefore, the following sections try to disclose the experiment program to achieve such an aim.”

3) The authors named different types of mixtures in Table 3 while did not use these IDs in the manuscript. So, what is the use of this table. Besides, “HMA143 pen” or “pen143 HMA”? Please keep it in a uniform statement. Also, what is pen143 stands for in local specifications?

Thank you for your comment.

Table 3 has been deleted and pen 143 HMA has been used in the manuscript.

53 pen and 143 pen grades of the bituminous binder were used for hard and soft HMA, respectively.

4) Please give a note on the one-to-one correspondence between microwaving duration and the final temperature in Figures 1 and 2. Otherwise, they look quite confusing, as the authors discussed about post-mix time while presented the post-mix temperature.

Thank you for your comment.

The traditional heated specimens were exposed to temperatures the same as the MW-heated specimens, across a range of time periods. The temperature of the specimens after microwaving for 2.5, 5, 7.5, and 10 minutes was recorded to be 76°C, 82°C, 90°C, and 101°C, respectively.

5) Were the trend lines in Figures 1 and 2 of any use?

Thank you for your comment.

The amendment has been done according to the reviewer comments.

This sentence has been added:

“Moreover, the trendlines for the ITSM with post-heating confirm the behaviour of the materials under different processing techniques, where there is optimum for MW processing ate 7.5 mins, while conventional heating needs extra time to reach the optimum.”

6) Figure 1 or 2 should be re-organized for a uniform style.

Thank you for your comment.

The amendment has been done according to the reviewer comments.

7) How many replicates were performed in each test? Error bars were missing in figures.

Thank you for your comment.

The amendment has been done according to the reviewer comments.

Error bars have been added to the required figures. In addition, this sentence has been added:

“It is worth mention that three replicates were performed in each test.”

8) What are the so-called “H.E, M.E, L.E” in Figure 3 and “A.H%, A.M%, A.L%” stand for? Are the MW power and MW energy the same thing in this manuscript?

 Thank you for your comment.

The amendment has been done according to the reviewer comments.

This information has been included in both Figures 4 and 5.

HML: High microwave level;

MML: Medium microwave level;

LML: Low microwave level

Regarding MW power and MW energy:

Microwave power is the power value supplied to the microwave magnet to work, while the energy is the quantity of the energy consumed by the materials from the power and it is dependent on the materials type and the polarity

9) The caption of Figure 5 is recommended to be revised to “Effect of MW time on ITSM of CBEMs containing 5.5 % PSA in terms of various curing times”. For Figure 6, “Impact of MW time on ITSM of traditional CBEM”. For Figure 7, “Correlation between accumulated creep strain and pulse count of various CBEMs”.

Thank you for your comment.

The amendment has been done according to the reviewer comments.

10) The Conclusion section too long to read, please shorten it to focuses on the key findings and make it more readable.

Thank you for your comment.

The amendment has been done according to the reviewer comments.

11) English writing should be re-checked throughout the text to avoid some minor grammar errors.

Thank you for your comment.

The amendment has been done according to the reviewer comments.

A native English proofreader has revised the manuscript.

In addition, the manuscript is checked for grammatical errors using Grammarly software. All typographical errors are now reduced to the publishing nearest minimum, as humanly possible.