Use of Waste Tires as Transverse Reinforcement and External Confinement in Concrete Columns Subjected to Axial Loads
Round 1
Reviewer 1 Report
In this research, the effect of using waste tires on columns confinement made by two different materials namely normal concrete and rubberized concrete is investigated experimentally. Sixteen specimens are fabricated, and examined under axial load. The results are compared and discussed in terms of Force-displacement curves.
The following comments should be addressed by the authors for enhancing the manuscript quality.
1. Following advanced studies discuss the application of rubber material in concrete columns and are worth being mentioned in the introduction:
a. Dabiri, H., & Kheyroddin, A. (2017). An analytical study into the seismic behavior of RC pier with elastomeric materials. ASIAN JOURNAL OF CIVIL ENGINEERING (BHRC), 18(7), 1183-1193.
b. Jia, J., Zhang, K., Saiidi, M. S., Guo, Y., Wu, S., Bi, K., & Du, X. (2020). Seismic evaluation of precast bridge columns with built-in elastomeric pads. Soil Dynamics and Earthquake Engineering, 128, 105868.
2. L149-159: the authors are highly suggested to add a figure illustrating the specimens for easier understanding the difference between the specimens.
3. Page5: the fabrication process of the specimens is not described. The authors should provide details regarding forms, concrete pouring, curing time and method. For instance, in confined specimens it is not clear if the tires are used as concrete form, or the tires are placed after concrete hardening!
4. L160-166: it is not clear the applied axial force is based on what criteria. Generally, the applied force is 0.1Agf'c. Is the same criteria used here, or the axial load is applied until the specimen failure?
5. The main concerns of the reviewer are: (a) confining columns by tires could cause lack of space between two columns which could be an issue in terms of architectural design. (b) why are the specimens not reinforced by steel bars? If only the compressive strength of concrete is the matter of this research, small samples might be sufficient! (c) Why unconfined columns are not fabricated with the same diameter of the confined columns, for the sake of better comparison between samples? These questions should be clearly explained by the authors in the revised manuscript.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Journal: Sustainability (MDPI)
Title: Use of Waste Tires as Transverse Reinforcement and External Confinement in Concrete Columns Subjected to Axial Loads
The authors have presented a research concept that aims to address the issue of waste tyres while improving the strength and performance of concrete structures by using recycled rubber tyres as confinement in concrete columns. Authors have tried to illustrate the viability of using waste rubber tyres on concrete columns, which will enhance the strength and ductility of columns and reduce environmental concerns from the damping of used tyres. However, the review hasn’t shown the gaps in previous findings and the concrete contribution of the research.
So, it needs major modification to make it publishable as scientific research journal. The concerns are presented as follows:
Key comments
1. First of all, it is suggested to rewrite the whole article in the proper format. (such as 1. Introduction, 2. Experimental Works, 2.1… Materials and specimens’ specifications, etc.)
2. The initiation of introduction is somehow satisfactory; however, it was not clear about the contribution of the study and how the study intends to fill the research gap. The significance and relevance of the findings will therefore be clear to the readers.
3. In practice, generally, the novelty and brief investigation process, along with probable findings, should be mentioned at the end of the introduction section. But, in this manuscript, this was missing. So, it is suggested to rewrite the introduction section by mentioning previous findings and the concrete contributions of this study.
4. If possible, provide a quantitative comparison of the performance of rubberized concrete rather than qualitatively (lines 66–67) from past studies. So, the reader can get it easily.
5. Normally, the variables would be written in italic font (such as: fcc) – line [98].
6. In Chapter 2 (materials and methods), as per the authors, the recycled tyres were used for two purposes; one as a replacement for normal concrete and another for confinement. The first is viable, but is the second reliable in practice? Need concrete justification that the whole tyre can be used as confinement in real work?
7. In same section, it was depicted that more than 47% extra cement was added to get same strength of rubberized concrete as normal aggregate concrete, it is suggested to provide key reason of its consequences.
8. Text font size in figure need to be aligned with the text in main body (Fig. 1.1, 1.2, 1.3, 1.4 and 3.22).
9. Check the quantities of samples [line 135-136 and line 150-159].
10. It would be clearer to reader if the “materials and method” section describe separately [ such as :2.1 material specifications, 2.2 methods and instrumentation]
11. It was missing the instrumentation for measurement of axial deflection/deformation.
12. The result section seems too lengthy, it is suggested to combine result and discussion in one section (3. Result and discussion), the discussion section is too wordy, so try to make compactable with concrete findings,” if possible, make a small comparison with concrete finding from all experimental data, so reader will get easier to compare the finding.
13. It would be advisable to compare the test result with other confinement techniques in previous studies: Key papers should be discussed and included in the introduction. And the authors should also try to compare the confinement model from the current Model code or those proposed in previous studies.
§ Abdullah, W., Omar, A., & Rafiq, S. K. (2021). Experimental Work on Using Fully Wrapped Post-Tensioned Metal Straps Around Normal Reinforced Concrete Beams to Increase Flexural Strength of RC Beams. Sulaimania Journal for Engineering Sciences, 8(1).
§ Garcia, R., Pilakoutas, K., Hajirasouliha, I., Guadagnini, M., Kyriakides, N., & Ciupala, M. A. (2017). Seismic retrofitting of RC buildings using CFRP and post-tensioned metal straps: shake table tests. Bulletin of Earthquake Engineering, 15, 3321-3347.
§ Imjai, T., Chaisakulkiet, U., Garcia, R., & Pilakoutas, K. (2018). Strengthening of RC members using Post-Tensioned Metal Straps: state of the research. Lowland Technology International, 20(2, Sep), 109-118.
Research works on analytical confinement model:
§ Ma, C. K., Garcia, R., Yung, S. C. S., Awang, A. Z., Omar, W., & Pilakoutas, K. (2019). Strengthening of pre-damaged concrete cylinders using post-tensioned steel straps. Proceedings of the Institution of Civil Engineers-Structures and Buildings, 172(10), 703-711.
§ Imjai, T., Setkit, M., Garcia, R., & Figueiredo, F. P. (2020). Strengthening of damaged low strength concrete beams using PTMS or NSM techniques. Case Studies in Construction Materials, 13, e00403.
14. It would be better to add “conclusion” section and provide the clearer result by linking with the problem of the statement, then it will be specific conclusion.
15. There are minor typos in the manuscript; checking the typos and grammatical odds thoroughly is suggested.
16. The conclusion is not so satisfactory. The conclusion and the problem the statement should interlink, so, the authors should try to present a concrete conclusion rather than a generic focusing to justify the theme of study.
17. There are minor typos in the manuscript; checking the typos and grammatical odds thoroughly is suggested. Native speaker should be employed to improve overall text quality.
18. Reference need to be consistence. Follow the journal guideline.
There are minor typos in the manuscript; checking the typos and grammatical odds thoroughly is suggested. Native speaker should be employed to improve overall text quality.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
This is a very interesting paper on the use of rubber tires in construction of concrete columns. The authors analyze both the use of tires as external transverse reinforcement, showing a 50% increase in the axial compressive test of rubber tires-confined columns.
Although the authors do mention that future research should address the issues of physical properties of waste tires (to understand their wear and tear), this subject must be addressed in more detail. Namely, tire aging is the very reason there are waste tires. The lifespan of an average tire is usually only 6 years, maximum 10 years, as the rubber compound harden with time and the tire is more likely to crack. The authors should mention at least the approximate average age of tires they used in their experiments.
Also, the tire aging is related to oxidation, as the rubber dries out and becomes stiffer when exposed to oxygen. Do the authors think that the rubber-concrete contact would lead to acceleration of rubber aging or quite the opposite?
I recommend this paper for publication after the authors address the aging issue in more detail – please add a paragraph or two, at the least.
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
Dear authors, the issue of recycling used tires is really very important and your research is very relevant. Despite this, for a better perception of the results of your research by readers, I propose to make some adjustments to it:
1. Equations must be formatted as equations, not text.
2. It is necessary to add subsections Literature review and Problem Statement of the problem to the Introduction section. In addition, it is necessary to include in the Introduction section the purpose of the work, the main tasks and the further structure of the article.
3. Tables 2.1, 2.2 and 2.3 need to be merged.
4. Based on the data given in Table 2.4 it is not clear what kind of samples were examined. We need to describe them in more detail.
5. Fig. 2.1 can be excluded.
6. You need to add a Conclusions section.
7. In section 4, you must add links to similar works and compare the results obtained in them with your own results.
8. The Results section should be shortened by eliminating duplicate data.
9. Equation 3.4 and the equation in Fig. 3.23 are the same, on the basis of which the equation in Fig. 3.23 needs to be removed.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The revised m/s has improved according to the reviewer's comments. It is suggested the revised m/s can be accepted in the present form.
Reviewer 4 Report
Dear authors, I have satisfied a new version of the article.
