Review Reports

Round 1

Reviewer 1 Report

This revised paper presents an analysis of the influence of  Guayule Resin on crumb tire rubber modified bitumen properties. The topic chosen is very interesting and  would be of interest to the readers recycling.

In general, even though the discussion has been improved, the paper is still puzzy.

 For example, section 3.1 seems a mere  list of the outcomes and does not present a proper discussion.

Regarding interrupted shear flow, I am not convinced yet that it can be done with a CS rheometer.

 

 Some other comments  :

·        It is no clear if BGr is solu8ble in AC

·         Some master curves show a thermocomplexity that deserves to be mentioned

·        No chemical characterisation of Guayule Resin is reported

·        Guayule Resin presents an interesting behaviour at low frequencies, tending to develop a plateau that deserves to be studied in detail

·        These Resins usually tend to undergo a notable ageing, Any information??

Consequently, I believe the present form of the manuscript is not suited for publication.

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This is an interesting paper evaluating the effect of guayule resin as a bio-based additive on asphalt rubber binder. Overall, this manuscript is good research paper; however, please consider the following comments for possible improvement:

provide some background on rubber binders other than these relevant to guayule resin alone, this has been a big/hot topic for years, one direction is to collect some latest studies. try not to use too many parenthesis to add/explain information, in most cases, only disturb the structure, making sentences difficult to read. too many abbreviations, AC, CRM, BGR, AR, etc., making the manuscript difficult to read. be straightforward, for example, lines 82-91, what exactly is the objective? maybe eliminate these irrelevant information.  overall, too much details. Present the most important information with a good logic. It's good to have these details but too many get people lost, especially, the key message is not clear. An example, table 2 has a lot of good information, but this is a section called experimental plan, should not involve too much detailed data.  Better structure this manuscript, e.g., section 3.5.5.2 may be too much for a research article., a flowchart is needed for the experimental plan.  what's the conclusion of this study, can't find it from the section of "conclusion", which only summarizes the detailed findings. 

 

Author Response

Response to Reviewer 2 Comments

Provide some background on rubber binders.

In the introduction, a paragraph has been added to support literature in terms of asphalt-rubber binders (Lines 73-89).

Do not use too many parenthesis or too many abbreviations, AC, CRM, BGR, AR, etc.

The parenthesis and abbreviations have been minimized as much as we can, aiming to eliminate confusions that may face the reader.

What exactly is the objective?

The paper’s objective paragraph has been rephrased to reflect the major objective in simple statements (Lines 98-107).

Table 2, too much information irrelevant to a section called experimental plan (should not involve too much detailed data).

Table 2 has been transferred to its appropriate location (Section 3, Lines 281-284) with minimizing its contents, focusing on the beneficial information that serves for the manuscript context.

Better structure this manuscript, e.g., section 3.5.5.2 may be too much for a research article.

The authors have adjusted the manuscript structure to be better, including the long sections numbering that has been substituted. In addition, some sections have been adjusted to serve for the manuscript’s context in a straightforward statements such as Section 3.1 (Lines 268-291).

Flowchart is needed for the experimental plan.

Flowcharts have been added to simplify the sequence of the experimental plan (Figure 1, Lines 168-171).

What’s the conclusion of this study? – Conclusion section just summarizes the detailed findings.

The conclusion section has been entirely adjusted to reflect the paper’s conclusion (Lines 508-530).

Round 2

Reviewer 2 Report

Some figures do not have color for x-,y-axles, please check them out. The revision reads much better. 

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

 

Round 1

Reviewer 1 Report

1. Enhance the introduction part if possible.

2. Highlight your own contribution?

Author Response

  Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The topic of the paper is very interesting for the civil engineering scientic community. The scientific approach is very sound, based on the up to date lab methods in pavement engineering. The main results are relevant and properly discussed. Overall, it is an excellent paper.

Author Response

  The topic of the paper is very interesting for the civil engineering scientific community. The scientific approach is very sound, based on the up to date lab methods in pavement engineering. The main results are relevant and properly discussed. Overall, it is an excellent paper.

   Thank you so much!

 

Reviewer 3 Report

I highly recommend validating the results by conducting a simple mixture test

Author Response

  I highly recommend validating the results by conducting a simple mixture test.

   Response 1: The authors agree with you that ultimately, the trigger point is to validate the binder performance with the mix performance as the final destination for real applications. The authors put this point in their considerations, and hopefully, they will apply that in a separated paper to explain this research point in further details.

 

Reviewer 4 Report

This paper presents an analysis of the influence of  Guayule Resin on crumb tire rubber modified bitumen properties

The topic chosen is very interesting and  would be of interest to the readers recycling.

In general, (with some exceptions) this study is well performed and the methods used are appropriate, with an interesting and quite extensive experimental part. However in some parts the layout of the manuscript is not adequate. For example, section 3.1 seems a mere  list of the outcomes and does not present a proper discussion.

Regarding interrupted shear flow, I do not agree with authors conclusions. Firstly, author should explain better the experimental conditions and the propose of the test.. Secondly, a control stress  rheometer is not the best alternative to perform this type of control rate test. In line with this, the first point in graph 6 is at 5 s in a linear scale and therefore a lot of essential information is missed at lower times, and most probably this is the reason of the constant values found. It is pretty sure that an overshoot could be found at lower times. In addition, I wonder why authors  chose a shear rate of 2 s-1 which is relatively high to observe structural effects.

. Some other concerns are shown below:

·        No chemical characterisation of Guayule Resin is reported

·        Although superpave uses G*/sinδ as a key parameter, in my opinion, for an frequency sweep it is better to discuss in term of G´, G´´ and δ separately.

·        Guayule Resin presents an interesting behaviour at low frequencies, tending to develop a plateau that deserves to be studied in detail

Consequently, I believe the present form of the manuscript is not suited for publication.

 

Author Response

  Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 4 Report

This paper presents an analysis of the influence of  Guayule Resin on crumb tire rubber modified bitumen properties. The topic chosen is very interesting and  would be of interest to the readers recycling.

In  my opinion the revised version is on sufficiently  improved, especially the rheological tests:

·        Interrupted shear flow: a control stress  rheometer is not the best alternative to perform this type of control rate test. In addition, the main interest of this test is at short times (below 5 s) otherwise a lot of information is missed.

·        Although superpave uses G*/sinδ as a key parameter, in my opinion, for an frequency sweep it is better to discuss in term of G´, G´´ and δ separately.

·        Guayule Resin presents an interesting behaviour at low frequencies, tending to develop a plateau that deserves to be studied in detail

Consequently, I believe the present form of the manuscript is not suited for publication.