Optimization of Mechanical Performance of Full-Scale Precast Concrete Pipes with Varying Concrete Strengths and Reinforcement Using Factorial Design

Abbreviated Comment of Reviewer #1

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This paper present a systematical study on mechanical performance of full-scale concrete pipes using the three-edge bearing testing method. Several suggestions are proposed for possible improvement of this manuscript.

Thanks for the reviewer’s feedback. All suggestions of the reviewer has been incorporated in the revised manuscript.

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Abbreviated Comment of Reviewer #1

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(1) In the 2nd section of this paper, the author presented the survey data of relative lower compressive strength of concrete than the required compared with the ASTM C76 for the local manufactured pipes, as both concrete compressive strength and reinforcement levels were discussed in this study, could you please also present the survey data of reinforcement levels for the local manufactured pipes if possible?

As suggested, the survey data of reinforcement levels for the local manufactured pipes has also been added in the revised manuscript.

Page 4, Lines 196, 197; Figure 2

(2) The 6th conclusions section need to be simplified, please present the main findings of this study in the conclusion part.

As suggested, the conclusion section was re-written to present the main findings in the revised manuscript.

Summary and Conclusion section (Section 7)

(3) This study presented the current state of local manufactured pipes' qualities which often did not satisify the requirements of the specifications such as ASTM C76 according to the details of the paper's 2nd section, after the systematical full-scale experiments and analysis of this study, could any suggestion be proposed to help improve the quality and mechanical performance of concrete pipes for the local pipe fabrication plants?

 Yes, this study presented the current state of local manufactured pipes' qualities which often did not satisfy the requirements of the specifications such as ASTM C76 (especially for concrete strength). Therefore, the systematic full-scale experiments and analysis were conducted to address the issues related to quality and mechanical performance of concrete pipes casted through local spun cast technique already available in fabrication plants in two ways:

1)      The use of optimized concrete materials will improve the strength and durability of the produced pipes. Therefore, using high-quality, locally sourced materials that meet the necessary standards can also enhance the performance of the final product and add more profit margin for the fabricator.

2)      The improved reinforcement technique in pipes suitable for spun cast methodology plays an important role towards the improved performance of casted pipes. Therefore, the exact optimization of reinforcement with respect to targeted pipe Class, meeting the ASTM C76 requirement, will assist the local pipe stakeholders for gaining confidence on the casted pipes using already installed spun cast technique.

Moreover, this approach not only seeks to improve the overall quality of the pipes but also strives to establish more efficient, cost-effective manufacturing practices, thereby contributing to the growth of the pipe industry leading to enhancement in the profit margin of the local fabricators. Ultimately, the findings are expected to support the development of higher-performance infrastructure solutions in developing economies.

Discussion and Conclusion sections

Abbreviated Comment of Reviewer #2

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The manuscript is well-organized and addresses a relevant topic in the field of civil and infrastructure engineering. The study investigates the design and optimization of precast concrete pipes, by performing a series of three edge bending tests on real concrete pipes.

The author is very grateful for the reviewer’s encouraging feedback.

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Abbreviated Comment of Reviewer #2

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1.  The abstract effectively summarizes the study but could be improved by stating the practical implications more explicitly, e.g., how the findings could influence design standards or industrial practices.

As suggested, the abstract was improved in the revised manuscript.

Abstract

2. The introduction establishes the context well, but it is recommended to clearly define the research gap earlier in the section. References to recent works are helpful, ………..

As recommended, the research gap has been added in the revised manuscript. Moreover, recent/latest references have been added in the revised manuscript.

Introduction section; Lines 121-184

3. In the data analysis, it would be beneficial to include more details on error quantification and potential experimental limitations.

More details on error quantification (standard deviations of the crack load and ultimate load) have been added in the revised manuscript.

Moreover, the potential experimental limitations of conducted three-edge bearing test have been mentioned in the revised manuscript.

Table 4;

Page 10, Lines 285-295

4. As displacement transducers were placed, it will be helpful if the displacement vs load curves can be presented. 

As suggested, load versus deflection plots of tested pipe has been added in the revised manuscript.

Figure 14

Abbreviated Comment of Reviewer #3

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This paper studies the influence of concrete strength and steel reinforcement ratio on the mechanical properties of prefabricated pipes by comparing the ultimate load and the corresponding load of crack width.

The author is thankful for the reviewer’s comments.

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Abbreviated Comment of Reviewer #3

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1. In the mix ratio of prefabricated pipes, the water-cement ratio is too large, which is a bit beyond the norm

The water to cement (w/c) ratio in the used mixture design was 0.39, 0.45 and 0.73 for 20 MPa, 30 MPa and 40 MPa targeted concrete compressive strength, respectively. These used w/c ratios are normally employed in the local construction industry for casting the prefabricated pipes using spun-cast (spinning) methodology. The w/c ratio has a direct influence on the compressive strength of concrete mixture. Higher w/c ratio will lead to lower compressive strength. According to ASTM C76, the minimum compressive strength for casting of concrete pipes should be 27.6 MPa and water to binder ratio should not exceed by 0.53 (Abbas et al., 2025). However, in the local practice, higher water to binder ratio is being used which ultimately effect the strength properties.

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2. What is the basic performance of steel bars? The article does not mention it. The basic performance of steel bars has a great influence on the overall mechanical response.

The basic performance/information of used steel rebar has been added in the revised manuscript.

Page 7, Lines 235, 236

3. Why is the load-displacement relationship curve not shown in the article? Isn't this a better comparison indicator when comparing the stiffness of the specimens?

The load-displacement relationship curve has been provided in the revised manuscript. Further comparison of stiffness has been added in the revised manuscript.

Figure 14; Page 13, Lines 370-378

4. Some other minor issues

(1) The references are old

(2) Please reconsider the keywords 

(3) The part about the experimental test program is suggested to be more detailed.

New references have been added in the revised manuscript.

Keywords have been rewritten/changed in the revised manuscript.

As suggested, more details regarding experimental test setup have been added in the revised manuscript.

Lines 121-138

Lines 39, 40

Section 4: Testing methodologies