Performance Evaluation of Recycled Asphalt Pavement Materials and Cold Recycling Mixtures Designed with Vibratory Compaction Method

Round 1

Reviewer 1 Report

The article is interesting and important for modern science, but requires several additions:
1. Unfortunately, in the article text it is difficult to find information for what number of test samples the individual determinations were carried out.

2. Are trend changes analyzed based on average values ?  If so, the average values were calculated based on what number (how many) of observations?

3. The graphs show 3, 4 points. It seems that this number is insufficient to present the function of the trend, especially when the changes take place in time. The justification for such an approach would be that the average was calculated based on a significant number of results, using the observation weights method.

4. Drawings included in the text are not of the best quality which makes their interpretation difficult. Resolution of the images too low.  In addition, the style and size of the font should be unified. Units should be in aquare brackets. Different letter characters in horizontal and vertical descriptions (e.g. Fig. 6.).

5. I also suggest formatting literature in accordance with the requirements of the Journal.

6. For consideration - the title should rather use the whole name of the material group (recycled asphalt pavement) and not its abbreviation (RAP) due to the fact that the explanation of the abbreviation appears only in the text (in the abstract).

Author Response

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Reviewer 2 Report

(1)    Are there any references missing for Lines from 39 to 72? Please double check.

(2)    Is it necessary to keep so many literature review results in the “Introduction”?

(3)    In Line 109, are the three RAP materials same or not? Please elaborate.

(4)    Please double check the format and grammar in this manuscript.

(5)    Please illustrate what are the “three indicators of the aged asphalt” in Line 122.

(6)    Please explain what is “Specific Surface Area Analysis” and why do you need to do it herein.

(7)    Please add the full name of “UTM-25” when it firstly appears in this manuscript.

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

This paper indicates that a lot of work was done in order to study the effect of RAP in cold recycled mixtures but it is very difficult to follow. The expressions used are not accurate or they are unusual; the order of the explanations is not clear and complete. I recommend the authors to read this review and try to re-write the paper, simplify and clarify it, prepare schemes or flow charts that help following the paper.

Abstract

It is not clear. What is “cluster strength”? What does “the vibratory compaction method was recommended according to the maximum dry density of mixtures” mean? And “evenly mixed”, “solid content”, “Indoor-short term test”?

 

Introduction

I recommend the authors to focus on the properties that are studied in the work described. Some references are cited but they are not related to the conclusions or findings.

There are sentences that seem incomplete, like that of Line 40: “A conducted physical performance testing and strength testing of RAP materials in the laboratory.”

There are many sentences and words that are not fully understood, and statements that are not clarified. For example:

Line 76: what is Wim method? Could the authors give a reference?

Line 77: the usual word for the Superpave compactor is gyratory, not rotatory.

Line 102: the usual expression for “black stone” is “black rock”.

Lines 97-98: when authors speak about heavy-duty compactor, are they referring to impact compaction? Is this a Proctor compaction method? According to the explanations given some pages later this is what it seems to be but it is not written.

Materials and Experiments

This section is not complete. The second part of the study (Performance and affecting factors of vibratory …) has no methodology explained in this section.

Line 127: What does “according to the actual engineering data” mean?

Line 129: how was the specific surface area calculated?

Line 135: when authors write “grades”, do they mean “sizes” or “fractions”?

Lines 136: what does “pores” mean here?

Triaxial test

Lines 140-141: what is the change done with the confining pressure? Please, explain.

Line 148: Do “extracted RAP materials” mean “RAP aggregate”?

Lines 146-149: the cases studied are suggesting that cold recycling is going to be compared to half-warm recycling? This is a different recycling technique and it is important to mention this objective as part of the study carried out.

Section about mortar cementing method

How do authors use the method? It is not clear. Do they substitute cement and sand with RAP? How? Do they use Portland cement? If authors combine cement and RAP, the resistance may be due to both binders but also to reactions between them; was this issue analized or taken into account?

Line 157: what do authors mean with “old material particle group”? Is this RAP?

Line 159: similar to 158, what is “old aggregate particle group? Is this RAP aggregate?

Line 160: extrapolated to what?

Lines 163-164: does it mean that sand was replaced with RAP?

Line 165: what are these percentages related to?

Line 169: instead of “test piece”, it should be specimen.

This section does not describe the methodology for compaction and properties evaluated.

Lines 180- 193: this paragraph is true but is not part of the results. This can be part of a state of the art or introduction.

Figure 4: title and legends are not clear: what does “extraction is advanced” mean? Was this result obtained from an intermediate time of the extraction? It is usual to show the results “before” and “after” extraction, but not “extraction is advanced”.

Line 219: authors write “the new cement added”. Is this a mistake? Do they mean “emulsion”?

Line 220: when authors write “old cluster”, do they mean “RAP lump”?

Specific surface

Line 221-244: how was specific surface calculated?

Figure 5: what is “add new material”? Legend: what does “pumping ahead” mean”? It is important to show the composition of this mix. What is the amount of mineral powder (filler)?

Residual cohesion of RAP Materials
Line 261. What does “foreign materials” mean?

Line 266: what do authors mean with “rolling”? Do they mean “compaction”?

Line 271: it is 24 h, not 12 h.

Line 271: when authors write “thermal recycling”, are they speaking about “warm” or “half-warm recycling”?

Figure 7: what is the ratio calculated for “mortar mixing ratio”? Explain the calculations.

Title of figure 7: what is “old cement mortar particle cluster”?

Figure 8: how was “cement consumption” calculated? Explain.

Lines 295: what is the current specification for the spitting strength of the cold RAP materials?

Line 313: what do authors mean with “strength composition”?

Line 313: what do authors mean with “traditional road engineering materials”? Do they mean hot mix asphalt?

Lines 316-316: what is “strength composition characteristics”?

Performance and affecting factors of vibratory compaction emulsified asphalt cold recycling mixture

With “emulsified asphalt”, do authors mean “emulsion”? If so, what type of emulsion was used?

Is the heavy duty compaction a kind of Modified Proctor Compaction?

Line 335-337: what was the mixing time?

Paragraph 338-346 is difficult to understand.

Line 339: what is “wetting water”? Is it additional water to that coming from the emulsion? If so, it is difficult to think that a cold recycled mixture can be compacted without additional water. What was the optimum fluid content obtained from the compaction analysis?

Table 2: what is QA, QB, QC and QD? Four different gradations or four different mixtures? Is gradation the only difference among the mixtures?

Line 355: what is “solid content emulsified asphalts”? what is the meaning of “solid” here?

Line 370: what is “occasional watering”?

Figures 9, 10, 11 and 12: indicate title and units in the axes. These figures show that vibratory compactor allows achieving higher density than heavy-duty compactor. The compaction degree depends on many conditions (weight, time, vibration frequency, etc.). So, it would be interesting that the authors explain both methods in detail.

Line 398: what is the “maximum dry density on site”? This value was not cited in the manuscript. Was a comparison with a field trial carried out?

Figures 14 and 15: the titles of the axes are exactly the same. X-axis in figure 15 should be “measured moisture”.

Lines 438-439: what is the “law of intensity growth”?

Figure 17: why do authors use the words “health” and “Hygiene” to describe the curing conditions?

Figure 18: is this figure showing the results of indirect tensile strength? Again, why do the authors use the words “healthcare” and “health”?

 

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The revised version looks much better than before. Minor grammar revisions are recommended for publication.

Author Response

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Reviewer 3 Report

This reviewer would have preferred an additional manuscript replying to all the questions asked and explaining all the doubts put forward. However, the changes made are appreciated and assessed as adequate. There are some comments that must be cited still.

Title: it is still a little confusing.

Introduction, lines 37-39: the format of citing researchers does not seem correct. Does the initial of the name go before or after the surname? These lines indicate the initial goes after but the following lines show the opposite. I am sure there must be instructions to follow.

Section 1.1.3, lines 122-124: please explain. Again, how is the specific surface area calculated? Do the authors use a specific test and equation to calculate it?

Section 1.3, line 169, and Figure 3: are the Marshall specimens shown in this Figure? The pictures do not seem Marshall shape, they look like prismatic  specimens.

 Section 2.4, line 312: what is the splitting strength of the cold RAP materials in the current specification?

 

Author Response

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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.