Mechanical Properties of PVC Fiber-Reinforced Concrete—Effects of Fiber Content and Length

Round 1

Reviewer 1 Report

The submitted work investigates the mechanical properties of PVC fiber reinforced concrete. Six concrete mixtures were produced using plastic fibers obtained from PVC clear sheets. The selected fibers were 20 mm and 40 mm in length with a width of 2mm. The fiber content was varied in the range of 0–1.5% for each fiber length. The fresh concrete mixtures were tested for workability in terms of slump. The hardened concretes were tested for compressive and splitting tensile strengths, flexural strength and toughness, static elastic modulus, and impact resistance and toughness.

In general, the paper is extremely well written, the results are clearly presented, and the conclusions are supported by the results. The introduction is quite complete, and the problem is well established. In the opinion of this Reviewer this study is worthy of publication after minor revision and is very useful for practical use. However, this Reviewer has some recommendations and questions, as described below:

1.   How many concrete specimens were constructed and tested for each experimental procedure?

2.   Section 3.3.3: The Authors should include a figure with the cracking pattern of the tested specimens under three-point loading procedure.

3.  Section 4: The Authors should collect the experimental results from all testing procedures in a table. It could be more helpful for the readers to understand the contribution of the PVC fibers in concrete matrix.

Author Response

Responses to the Reviewer's Comments:

Comment 1: How many concrete specimens were constructed and tested for each experimental procedure?

Response: We have clarified it in Section 3.3.2, Section 3.3.3, and Section 3.3.4.

Comment 2: Section 3.3.3: The Authors should include a figure with the cracking pattern of the tested specimens under three-point loading procedure.

Response: We have included the image of a tested beam specimen with the cracking pattern in Figure 5.

Comment 3: Section 4: The Authors should collect the experimental results from all testing procedures in a table. It could be more helpful for the readers to understand the contribution of the PVC fibers in concrete matrix.

Response: All the experimental results are shown in Table 4 (newly included) and Table 5.

Reviewer 2 Report

Comments for author File: Comments.pdf

Author Response

Overall Comments: This paper examined the fiber content and length derived from waste PVC on the mechanical properties of concrete. Although the paper is well written and very easy to read and follow, the novelty component of this paper is non-existent and the conclusions does not contribute to knowledge. In fact, the literature contains vast amount of information about the effect of the 
amount and length of PVC fiber on the mechanical properties of concrete. This work is simply a repetitive of previously published work in this area.

Response: Authors added a short description of the novelty of their research work mentioning the previous work regarding the impact performance of non-PVC plastic fiber reinforced concrete (please see Section 2). The present study focused to have a comprehensive understanding of the impact resistance of PVC fiber reinforced concrete along with other major mechanical properties. Further clarification has been made by revising Section 1.

Comment 1: No information is provided about the properties of PVC fiber used in this study, specifically, its tensile strength, % elongation, stress strain curve, etc. This is a crucial point missing. As now, these tests can’t be replicated.

Response: Thank you for your thoughtful review and for pointing out the absence of specific properties of the PVC fiber in our study. We appreciate your diligence in evaluating our manuscript. We would like to address your concern in a future research project. The project related to the present study has been concluded - the students have already graduated and left the university. Also, this limitation is due to resource constraints and logistical challenges beyond our control at present. We acknowledge that the absence of the above-mentioned specific properties of PVC fiber is a limitation of our work. We have clearly highlighted this limitation in the revised manuscript (please see the conclusion section).

Comment 2: What is the rationale for selecting the fiber content (0.5%, 1%, 1.5%)? Any references?

Response: Thank you for the comment. The selection of fiber contents (0.5%, 1%, 1.5%) was accomplished based on the published literature on both non-PVC and PVC plastic fibers, as detailed in Table 1 of our manuscript. We found from literature that the strength contribution of PVC fibers beyond 1.5% is minimal. Additionally, it's important to note that the mixing operation becomes quite challenging due to the low workability of the concrete mix at higher fiber contents.

Comment 3: The authors used in this study a high-water cement ratio 0.58. this should be enough for obtaining an appropriate slump. So, what is the reason for adding a superplasticizer?

Response: Although a water-cement ratio of 0.58 would typically provide an acceptable slump in concrete mixtures, the incorporation of a superplasticizer in our study serves several critical purposes. The addition of PVC fibers to the concrete mixture reduces its workability, and superplasticizers are influential in improving the workability by reducing the water demand while maintaining the required slump or flow. Additionally, superplasticizers facilitate better dispersion of the fibers within the concrete mixture. This is advantageous because it can result in improved mechanical performance of the concrete.

Comment 4: In Sec 3.3.3, the authors state the following “a dial gauge was placed at the beams central bottom line”. However, the dial gauge can’t be seen in Figure 5b.

Response: Thank you for the comment. The photo of the flexure test added in the previous version of the manuscript was before the placing of the dial gauge. The complete flexural strength test setup under three-point loading is shown in Fig. 5 (b) under section 3.3.3 in the revised manuscript.

Comment 5: The shear span depth ratio is not stated in the paper and its value appear very small. Therefore, the flexural behavior and flexural strength results are significantly affected by this ratio.

Response: Shear span to depth ratio (a/d) for the specimen was 1.67. According to ASTM C293/C293M, for the center point loading procedure, the total span should be three times the average depth of the beam. The authors selected the beam dimensions and span for the loading in accordance with the requirements of the above standard.

Comment 6: The failure pattern of the beams containing different amount of fibers should be added to the paper. This may help provide scientific explanation for the flexural strength results.

Response: We appreciate the reviewer's constructive suggestion regarding the inclusion of failure patterns of the beams containing varying fiber concentrations in our paper. While we acknowledge the value of failure pattern analysis in providing scientific insights, we would like to inform you that our research primarily focused on the impact resistance and toughness of PVC fiber reinforced concrete. However, we will consider your suggestion in our future research where it aligns more closely with the research goals. However, in the revised manuscript, we have added one image of the post-failure beam specimen with cracking pattern (please see Figure 5).

Comment 7: In Figure 12, the flexural toughness for each mix needs to be determined in order to find the optimum mix.

Response: The flexural toughness values of different concretes were calculated from the areas under the load-deflection curves (Fig. 12) and are already shown in Fig. 14. In addition, the toughness values have been shown in Table 4. This table has been added newly based on the comments of the other Reviewer.

Comment 8: Correlations between the mechanical properties provided in Figure 16 are not correct. What is the reason for selecting the power relationship? Also did the authors try other types of correlation? The regression equations are valid only between the extreme points. Therefore, it totally unacceptable to draw the power relationship outside the boundaries under investigation. The plots should be corrected and plotted again.

Response: Thank you for the comment. The reason for selecting the power relationship was to explore the potential trends in the data that may not be linear. This approach allows for a more comprehensive examination of the relationships between the variables. However, we acknowledge the concern raised about the extrapolation of the power relationship beyond the boundaries of the data points. Upon careful consideration, we agree that it is essential to maintain the validity and accuracy of our analysis. We did explore other types of correlation methods, including linear and polynomial regressions, but found that the power relationship provided the best fit for the data within the investigated range. To address the concern and ensure the integrity of our findings, we made the necessary adjustments to the plots in Figure 16 in the revised manuscript. The power relationship is only applied within the bounds of the data points, and any extrapolation beyond those boundaries has been removed.

Comment 9: In Section 5 (Conclusion), the authors state “due to higher surface area that increased the water demand for a given slump”. How surface area increases the water demand?

Response: Thank you for the comment. When there is a higher volume of fibers in the concrete mixture, it tends to become more water-demanding, resulting in reduced workability, and thus hinder the flow of fresh concrete. Additionally, smaller-sized fibers can increase the water demand due to their increased surface area. In both cases, a greater amount of water is required for wetting material surfaces. The authors have revised Conclusion 1 and the associated section (Section 4.1).

Comment 10: In the conclusions, the authors need to mention clearly the limitations of their study.

Response: Thank you for your valuable opinion. The authors have clearly described the limitations of the study at the end of the conclusions.

Comment 11: A separate recommendation section is needed.

Response: Thank you for your valuable opinion. A separate recommendation section has been added.

Round 2

Reviewer 2 Report

The authors significantly improved the quality of their work in the revised version and addressed properly my comments. Although no issues, I recommend the authors to edit their paper one more time.