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Peer-Review Record

Experimental Evaluation of Untreated and Pretreated Crumb Rubber Used in Concrete

Crystals 2021, 11(5), 558; https://doi.org/10.3390/cryst11050558

by Hamad Hassan Awan¹, Muhammad Faisal Javed^2,*

, Adnan Yousaf², Fahid Aslam³

, Hisham Alabduljabbar³ and Amir Mosavi^4,5,6,*

Reviewer 1: Anonymous

Reviewer 2: Anonymous

Crystals 2021, 11(5), 558; https://doi.org/10.3390/cryst11050558

Submission received: 8 April 2021 / Revised: 6 May 2021 / Accepted: 6 May 2021 / Published: 17 May 2021

(This article belongs to the Special Issue Advances in Sustainable Concrete System)

Round 1

Reviewer 1 Report

Authors need to rewrite the introduction part and add more related references, also please highlight your contribution or considerations in your projects compared to others’ work since many researchers have done similar research before.
Please refine your conclusion part and add the discussions for your results. The effect or motivation of SEM results in your plan?
Any explanation about the test plan in your project? Any schedule? Any consideration?

Author Response

Reply to Reviewer 1 Comments

First of all, the authors would like to thank the editor and all the reviewers for suggesting improvements for the manuscript. Point-wise reply to each comment is made below Modifications/added lines are shown in Red color. All suggestions have been addressed, but still if reviewers have any other point/reservation, the authors are happy to incorporate.

Authors need to rewrite the introduction part and add more related references, also please highlight your contribution or considerations in your projects compared to others’ work since many researchers have done similar research before.

Reply: Thanks for your comment. The introduction part has been rewritten and more related references are also added. In this study the focus is on the surface treatment of the CR to mitigate the strength loss of concrete due to addition of CR. The majority of researchers has focused on additives, admixtures or increasing cement content in the CRC. This study aims at finding new, better and cheaper methods of surface treatments of CR to recover the strength loss of concrete by adding CR. The outcomes of this research study can be helpful in the practical application of using CR in the conventional concrete.

Please refine your conclusion part and add the discussions for your results. The effect or motivation of SEM results in your plan?

Reply: Thanks for your comment. The conclusion part has been refined and discussion are added for results in the relevant sections. Moreover, as the focus of this research was on surface treatments, SEM helped to look at the physical effects of surface treatments besides experimental results. SEM also helped in better understanding the experimental results.

Any explanation about the test plan in your project? Any schedule? Any consideration? ()

Reply: Thanks for your comment. The test plan was designed to check the performance of CRC and compared it with conventional concrete, in order to investigate the effectiveness of treatments in the CRC. For this purpose, “A total of 189 cylinders of 150 × 300mm for 21 mixes (as shown in Table 2 in the revised manuscript) were made for the research study. For each mix, 9 cylinders were made. 3 for assessing compressive strength at 7 days, 3 for assessing compressive strength at 28 days and 3 for assessing the indirect tensile strength at 28 days. Out of 21 mixes, 1 mix was used for controlled mix, 4 mixes were for untreated CRC, and 16 mixes were for treated CRC as shown in Table 2 (revised manuscript). 15 additional cylinders of 150 × 300mm were made to evaluate the compressive strength of untreated CRC at 28 days after placing the concrete specimen in oven at 200 °C for a time period of 6 hours.”

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript present experimental results for untreated and surface pre-treated crumb rubber, added to concrete as a partial fine aggregate (sand) replacement. The authors present results for fresh and hardened properties, including some SEM and residual strength after heating.

Overall, the results indicate some utility for the development of crumb rubber concretes, taking advantage of an under-utilised waste product. However, the analysis and discussion of the results presented is very limited; the reviewer strongly suggests that the authors expand significantly upon the interpretation and analysis of the results, rather than simply presenting the values - why are these effects observed? - before the manuscript is considered again for publication.

English language is generally good, except for a few places with some grammar and spelling that needs addressing (e.g.: lines 27, 31, 130-131, 302).

Referencing (1st author, year) is not consistent with the convention used in published papers in this journal.

Below are comments that should assist in enhancing the manuscript:

Line	Comment
30, 31	Use abbreviation for crumb rubber and crumb rubber concrete after first use (throughout manuscript)
27, 31	Spelling, grammar
33, 35	Number conventions (1,000 Million to 1 Billion)
39	Not sure what this is trying to say
58	Metakaolin (spelling); also some sentence structure revisions needed.
66	Volume or mass?
98-101	This should be simplified to make it clear to the reader
118-119	Could sieve data be added to Table 1 for comparison?
119	Any information on the detergent used?
121	The reviewer suggests re-arranging the mix design table to enhance clarity of the variations in mix design (Crumb rubber and Sand next to each other), and delineating between fine and coarse aggregates (above Sand and CR).
122	Table 3 should be located with results, not methods
122	Slump results should be in SI units (mm) to comply with use of SI units for other measures; also unit should be labelled in Table 3 header.
130-131	Grammar
150	Was the mixing following any Standard (e.g.: ASTM)?
151	Spelling
153-154	Was this following any Standard (e.g.: ASTM)? Lime-saturated water, or just water?
165	Figures presenting results are very difficult to read (size, lack of colour, shading)
171	Why is there an increase in slump? Is it perhaps due to a reduced available surface area with the CR? Sieve data would assist with this. Was there any relative trends between the different methods (relating to surface treatment and changes in available surface area)?
184	Compaction factor and slump are both testing the fresh properties of the concretes; perhaps combining the presentation and discussion of the results could be beneficial?
193	Please explain why the water-treated CRC showed the greatest absorption at 7 days (and smallest at 28 days), and what effects were observed with different treatments.
231-232	SEM or characterisation of the effect proposed, possibly of the ITZ?
246-249	Is this referring to untreated CR? It is difficult to ascertain
249-259	Add another figure showing the relative comparisons that you are discussing – this will provide a much easier method for the reader to interpret. Additionally, what are the implications or meaning of these findings?
260	This method was not mentioned in Section 2
272	Why is there a loss of tensile strength with CR addition? What is the cause of the effect? Is there any variation with treatment method (that is in the title of the paper, after all)?
302	Missing ‘Conclusions’ heading
302	Present vs past tense (evaluated)
327-355	The authors have not completed any of the Author contributions, funding, acknowledgements, or conflict of interest sections
356	Please check referencing, particularly [2] and [6]. The referencing convention used is inconsistent between the text and the References list (alphabetical vs numbered)

Author Response

Reply to Reviewer 2 Comments

Line

Comment

27, 31, 130-131, 302

English language is generally good, except for a few places with some grammar and spelling that needs addressing.

Reply: Thanks for your comment. The changes have been made in the revised manuscript in all the lines mentioned by reviewer.

30, 31

Use abbreviation for crumb rubber and crumb rubber concrete after first use (throughout manuscript)

Reply: Thanks for your comment. “Crumb Rubber” has been replaced with “CR” and “Crumb Rubber Concrete” has been replaced with “CRC” after first used throughout manuscript.

27, 31

Spelling, grammar

Reply: Thanks for your comment. The changes has already been addressed in comment 1.

33, 35

Number conventions (1,000 Million to 1 Billion)

Reply: Thanks for your comment. “1,000 Million” has been replaced with 1 Billion and “5,000 million” has been replaced with “5 Billion”.

Not sure what this is trying to say

Reply: Thanks for your comment. This line is referring to negative effects caused by “disposal” of waste tires. A comma has been added to understand the sentence more clearly. For further understanding the sentence has also been updated in the revised manuscript.

Metakaolin (spelling); also some sentence structure revisions needed.

Reply: Thanks for your comment. The spelling has been corrected and the sentence structure has been revised.

Volume or mass?

Reply: Thanks for your comment. The answer is “mass”. The sentence has been updated in revised manuscript.

98-101

This should be simplified to make it clear to the reader

Reply: Thanks for your comment. The sentence has been updated in the revised manuscript to make it clear to the reader.

118-119

Could sieve data be added to Table 1 for comparison?

Reply: Thanks for your comment. The sieve data for Crumb Rubber has been added in Table 1 in the revised manuscript.

119

Any information on the detergent used?

Reply: Thanks for your comment. The detergent used was obtained from local market which is used for washing clothes. The information has been added in the revised manuscript.

121

The reviewer suggests re-arranging the mix design table to enhance clarity of the variations in mix design (Crumb rubber and Sand next to each other), and delineating between fine and coarse aggregates (above Sand and CR).

Reply: Thanks for your comment. The table has been re-arranged according to reviewer’s comment in the revised manuscript.

122

Table 3 should be located with results, not methods

Reply: Thanks for your comment. Table 3 has been relocated with results in the revised manuscript.

122

Slump results should be in SI units (mm) to comply with use of SI units for other measures; also unit should be labelled in Table 3 header.

Reply: Thanks for your comment. Slump results are shown in SI units (mm) and units are labelled in Table 3 header in the revised manuscript.

130-131

Grammar

Reply: Thanks for your comment. The changes have been made in the revised manuscript in all the lines mentioned by reviewer.

150

Was the mixing following any Standard (e.g.: ASTM)?

Reply: Thanks for your comment. Mixing was performed according to ASTM C192 / C192M and is incorporated in the revised manuscript.

151

Spelling

Reply: Thanks for your comment. The spelling has been rechecked and updated in the revised manuscript.

153-154

Was this following any Standard (e.g.: ASTM)? Lime-saturated water, or just water?

Reply: Thanks for your comment. Curing was performed according to ASTM C192 / C192M and is incorporated in the revised manuscript.

165

Figures presenting results are very difficult to read (size, lack of colour, shading)

Reply: Thanks for your comment. Figures presenting the results are being updated in the revised manuscript.

171

Why is there an increase in slump? Is it perhaps due to a reduced available surface area with the CR? Sieve data would assist with this.

Was there any relative trends between the different methods (relating to surface treatment and changes in available surface area)?

Reply: Thanks for your comment. The increase in slump was due to poorly graded CR and high fineness modulus of CR. Furthermore, sieve data for CR has also been updated in Table 1 in the revised manuscript.

184

Compaction factor and slump are both testing the fresh properties of the concretes; perhaps combining the presentation and discussion of the results could be beneficial?

Reply: Thanks for your comment. The presentation and discussion of the results have been combined in the revised manuscript.

193

Please explain why the water-treated CRC showed the greatest absorption at 7 days (and smallest at 28 days), and what effects were observed with different treatments.

Reply: Thanks for your comment.

231-232

SEM or characterisation of the effect proposed, possibly of the ITZ?

Reply: Thanks for your comment. The suggestion has been incorporated in the revised manuscript.

246-249

Is this referring to untreated CR? It is difficult to ascertain

Reply: Thanks for your comment. YES! This is referring to untreated CRC. The changes have been incorporated in revised manuscript.

249-259

Add another figure showing the relative comparisons that you are discussing – this will provide a much easier method for the reader to interpret.

Additionally, what are the implications or meaning of these findings?

Reply: Thanks for your comment. The figure for relative comparisons has been added in the revised manuscript.

260

This method was not mentioned in Section 2

Reply: Thanks for your comment. The method has been discussed and can be found at lines 101-104

272

Why is there a loss of tensile strength with CR addition? What is the cause of the effect? Is there any variation with treatment method (that is in the title of the paper, after all)?

Reply: Thanks for your comment. This can be justified by, “The reduction in indirect tensile strength might be due to weak bonding between CR and cement. The ITZ acted as a micro-crack between the two materials. This weak ITZ accelerated the reduction in tensile strength”. The point is also been updated in the revised manuscript.

302

Missing ‘Conclusions’ heading

Reply: Thanks for your comment. The heading has been added in the revised manuscript.

302

Present vs past tense (evaluated)

Reply: Thanks for your comment. The sentence structure has been updated in the revised manuscript.

327-355

The authors have not completed any of the Author contributions, funding, acknowledgements, or conflict of interest sections

Reply: Thanks for your comment. The author contribution table has been inserted in the revised manuscript. In addition, funding, acknowledgements and conflict of interest section has been filled. The author contribution table is also inserted below for the convenience.

Author’s Contribution

author (1) conceptualization, data analysis, writing original draft preparation

author (2) Formal analysis and Modeling, conceptualization, data analysis, writing original draft preparation

author (3) Supervision, review and editing

author (4) Investigation and review

author (5) Methodology and review and editing

author (6) Review and editing, supervision

356

Please check referencing, particularly [2] and [6].

The referencing convention used is inconsistent between the text and the References list (alphabetical vs numbered)

Reply: Thanks for your comment. The references has been updated in the revised manuscript.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

It is good to highlight your contribution.

Author Response

No response is required here.

Reviewer 2 Report

Much improved manuscript. Overall, the reviewer does recommend a check of spelling and particularly grammar due to some awkward or poor sentence structures, and some missing spaces at some of the authors' revisions.

There are a few relatively minor comments to the updated manuscript:

1) Line 111-112: Was this oven heating following a standard for residual strength, and were the specimens allowed to cool (and how) prior to residual strength testing?

2) Line 178: Table 3 - it is best to use appropriate precision for slump results based upon the accuracy of the measurement method, as stated in ASTM C143 (Section 8). Also, please correct the value for CU20.

3) Line 181, 182: Please update according to SI units.

4) Line 196 - The not Then.

5) Line 262 - 280: How the 'recovered' metric was calculated is not clear; it is inferred that this is performance relative to the untreated CR?

6) Line 355: 'not worthy' is a normative statement. Recommend replacing with 'not suitable'.

Author Response

Response to the comments file is attached herewith.

Author Response File: Author Response.pdf

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Experimental Evaluation of Untreated and Pretreated Crumb Rubber Used in Concrete

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