Flexural Behavior and Composite Action of Structural Concrete Insulated Panels as Floor Slabs: Effects of Reinforcement Placement and Spacing

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The study focuses on concrete insulated panels as floor slabs, and an investigation was conducted on flexural and composite behaviour. The research experiment has been conducted in detail and explained well in the manuscript. I have the following comments for improvements of the manuscript.

1. Please provide some key numerical outcomes within the abstract.
2. The introduction section is a little too long and provides some general details about composite panels. I recommend that the section be shorter and only focus on the latest developments and some research findings.
3. Materials used: Could you provide a drawing with plan view and sectional view under this section? I noticed that views are provided in later sections, but I suggest providing detailed views under this section benefits the reader. The drawing could explain all the details mentioned.
4. …and after 28 days, it reached 2630 psi (18.13 MPa). I suggest using SI units throughout, as in the previous part of the writing.
5. In the description, it says that self-compacting concrete was used. The figure highlights that concrete of 1:2:4 for the top and shotcrete for the bottom were used. Please clarify.
6. Figure 5 shows Mu while the description shows Mn. Please correct and be consistent.
7. The graph in Figure 6 should be slightly revised to see the numbers on the axes properly.
8. In Figure 7, could you highlight the names of those marked circles?, What was the purpose of showing the circle?
9. The maximum moment and deflection graphs could be enhanced by including existing literature reviews, data, and design code limitations, for example, limitations from ACI are already highlighted in the writing.

Author Response

1. Please provide some key numerical outcomes within the abstract.

Response:
The revised abstract now includes key numerical outcomes:

“The findings reveal ultimate moment capacities ranging from 2.84 to 5.70 kN·m, and degrees of composite action between 6.5% and 28.2%. Notably, SCIP-2 and SCIP-3 satisfied ACI 318-19 deflection criteria...”

This addresses your request by adding precise quantitative results to help readers quickly understand the scope of the findings.

2. The introduction section is a little too long and provides some general details about composite panels. I recommend that the section be shorter and only focus on the latest developments and some research findings.

Response:
Your recommendation has been taken into the account and the introduction section has been made more concise and focused on latest developments and research findings.

3. Materials used: Could you provide a drawing with plan view and sectional view under this section? I noticed that views are provided in later sections, but I suggest providing detailed views under this section benefits the reader.

Response:
Yes, Figure 2 (sub-figures a–d) currently presents cross-sectional views of all four panel configurations. However, these are placed under Section 2.2 - Details of Specimens.

4. “…and after 28 days, it reached 2630 psi (18.13 MPa). I suggest using SI units throughout, as in the previous part of the writing.”

Response:
Manuscript has been updates to reflect this.

5. In the description, it says that self-compacting concrete was used. The figure highlights that concrete of 1:2:4 for the top and shotcrete for the bottom were used. Please clarify.

Response:

The text is updated as:

“The panels' top wythe was made of self-compacting concrete and bottom wythe was shotcreted…”

6. Figure 5 shows Mu while the description shows Mn. Please correct and be consistent.

Response:

Figure 5 shows a moment-deflection graph indicating composite action and have been updated accordingly.

7. The graph in Figure 6 should be slightly revised to see the numbers on the axes properly.

Response:

Visibility of the numbers and labels on axis has been improved.

8. In Figure 7, could you highlight the names of those marked circles? What was the purpose of showing the circle?

Response:

Figure 7 contains moment-deflection curves with marked points.

The description mentions “elastic (black) and maximum (red) points.”

9. The maximum moment and deflection graphs could be enhanced by including existing literature reviews, data, and design code limitations, for example, limitations from ACI are already highlighted in the writing.

Response:
The manuscript discusses ACI 318-19 deflection criteria and evaluates results accordingly (e.g., Table 5).

Reviewer 2 Report

Comments and Suggestions for Authors

Thank you for submitting your interesting work to Buildings journal. Please revise your manuscript according to the comments below.

1. You suddenly refer to sandwich panels in lines 39, 69, 75, 78, etc. Are you using that as a synonym for SCIP? Please correct this or remove this. Please be consistent throughout the article.
2. Lines 173-177 are not necessary or usual for a journal article. Please consider removing.
3. Please increase the font size of figures. They are not legible.
4. Lines 190-193-Please refer to the figure here.
5. Why did you use ASTM C109 for concrete compressive strength testing? ASTM C109 is the Standard Test Method for Compressive Strength of Hydraulic Cement Mortars. Also, if it was ASTM C109, did you test 2 in×2 in×2 in cubes? 2 in×2 in×2 in cubes is not the appropriate compressive strength test for structural concrete. Please correct.
6. Please round off the measurements to no more than 3 significant figures.
7. Line 337-“bottom wall”. Please correct to be consistent with previous sections.
8. Line 340, 341, 370-“fissures” is not commonly used for concrete. Please correct throughout the manuscript.
9. “Flexural cracks on the bottom wythe demonstrated a high degree of ductility”-how can a crack show ductility? Please revise this sentence for clarity.
10. Sections 4.2 and 4.3 both refer to figure 9. Please correct this. Also, include the specimen names in figures 8-11 to reduce confusion.
11. Line 532-what do you mean by “as the weight was progressively raised”? Do you mean the “load”? Please revise this sentence for clarity.

Author Response

Reviewer 1

Comment 1:
You suddenly refer to sandwich panels in lines 39, 69, 75, 78, etc. Are you using that as a synonym for SCIP? Please correct this or remove this. Please be consistent throughout the article.

Response:
Thank you for pointing this out. I have revised the manuscript to maintain consistency in terminology. All inconsistent references to "sandwich panels" have been corrected to "SCIP" or "Structural Concrete Insulated Panels" where appropriate.

Comment 2:
Lines 173–177 are not necessary or usual for a journal article. Please consider removing.

Response:
As suggested, the text from lines 173–177 has been removed from the manuscript.

Comment 3:
Please increase the font size of figures. They are not legible.

Response:
The font size of all figures has been increased to improve legibility and meet publication standards.

Comment 4:
Lines 190–193 – Please refer to the figure here.

Response:
A reference to the appropriate figure has now been included in this section to improve clarity.

Comment 5:
Why did you use ASTM C109 for concrete compressive strength testing? ASTM C109 is the Standard Test Method for Compressive Strength of Hydraulic Cement Mortars. Also, if it was ASTM C109, did you test 2 in × 2 in × 2 in cubes? 2 in × 2 in × 2 in cubes is not the appropriate compressive strength test for structural concrete. Please correct.

Response:
Thank you for catching this error. The reference to ASTM C109 was incorrect. I have corrected the standard to the appropriate one used for structural concrete testing (e.g., ASTM C39).

Comment 6:
Please round off the measurements to no more than 3 significant figures.

Response:
All measurements throughout the manuscript have been reviewed and rounded off to a maximum of three significant figures for consistency and clarity.

Comment 7:
Line 337 – “bottom wall”. Please correct to be consistent with previous sections.

Response:
This has been corrected to “bottom wythe” for consistency with terminology used elsewhere in the manuscript.

Comment 8:
Lines 340, 341, 370 – “fissures” is not commonly used for concrete. Please correct throughout the manuscript.

Response:
We have replaced the word “fissures” with more appropriate terms such as “cracks” or “cracking” throughout the manuscript.

Comment 9:
“Flexural cracks on the bottom wythe demonstrated a high degree of ductility” – how can a crack show ductility? Please revise this sentence for clarity.

Response:
Thank you for the observation. This sentence has been revised to: “The behavior of the bottom wythe under flexural loading reflected a ductile response, characterized by gradual crack propagation and distributed deformation.”

Comment 10:
Sections 4.2 and 4.3 both refer to Figure 9. Please correct this. Also, include the specimen names in Figures 8–11 to reduce confusion.

Response:
The figure references in Sections 4.2 and 4.3 have been corrected. Specimen names have been clearly labeled in Figures 8 through 11 to enhance clarity.

Comment 11:
Line 532 – what do you mean by “as the weight was progressively raised”? Do you mean the “load”? Please revise this sentence for clarity.

Response:
Yes, "load" was the intended term. This sentence has been revised for clarity and technical accuracy.

Reviewer 3 Report

Comments and Suggestions for Authors

Manuscript ID: buildings-3798100

Type of manuscript: Article
Title: Flexural Behavior and Composite Action of Structural Concrete Insulated Panels as Floor Slabs: Effects of Reinforcement Placement and Spacing

 

 

 

First of all, I would like to thank MDPI Buildings journal for providing me with the opportunity to serve as a reviewer.

This study investigates the flexural performance of Structural Concrete Insulated Panels (SCIPs), demonstrating their potential as a cost-effective, durable, and energy-efficient alternative to traditional floor systems. Four enhanced SCIP designs were tested under four-point bending to evaluate load capacity, ductility, and compliance with ACI 318 deflection limits.

Although the findings are relevant to the topic, the uncertainties and the adjustments outlined below need clearer explanation and further refinement.

 

1- The difference of this study from the existing literature, its potential contribution, and originality should be emphasized in the opening sentences of the abstract.

2- The most significant findings obtained from the study should be briefly presented with numerical data at the end of the abstract.

3- In the introduction of this study, it should be highlighted that, in addition to traditional 3- or 4-point bending tests and finite element analyses used to obtain load-deflection curves, machine learning methods have also proven to be highly successful thanks to advancements in AI. References to several related studies, as presented below, should be included to support this point.

- A hybrid data-driven machine learning framework for predicting the dynamic behavior of RCS slabs under wind-borne projectile impact

- Prediction of non-uniform shrinkage of steel-concrete composite slabs based on explainable ensemble machine learning model

- Machine Learning-Driven Flexural Performance Prediction and Experimental Investigation of Glass Fiber-Reinforced Polymer Bar-Reinforced Concrete Beams

- Nonlinear Load-Deflection Analysis of Steel Rebar-Reinforced Concrete Beams: Experimental, Theoretical and Machine Learning Analysis

- Enhanced XGBoost algorithm with multi-objective optimization for blast-induced response forecasting of RC slabs

 

4- The panel details presented in Figure 2 are not clearly readable. The visuals should be enlarged and made more easily understandable.

5- In Figure 4, it is observed that the metal plates used to apply the load in the four-point bending tests do not extend through the full thickness of the panels and therefore only affect the areas they are in direct contact with. This situation negatively impacts the fundamental principle of the four-point bending test. How do you justify that the tests conducted under these conditions accurately represent real-world behavior?

6- Why is Figure 5 unnecessarily large and of low quality? Please revise it.

7- The axis labels in Figure 6 should be repositioned and presented with greater attention to detail.

8- How does testing only one specimen of each panel type ensure the reliability of the study? At least three specimens of each panel type should be tested.

9-Reference numbers should be checked to ensure there are no errors.

10-It is recommended to review English grammar and spelling errors.

 

 

 

Author Response

Comment 1:
The difference of this study from the existing literature, its potential contribution, and originality should be emphasized in the opening sentences of the abstract.

Response:
As advised, the opening sentences of the abstract have been revised to clearly highlight the difference from existing literature, the originality of the approach, and the study's potential contribution.

Comment 2:
The most significant findings obtained from the study should be briefly presented with numerical data at the end of the abstract.

Response:
This suggestion has been implemented. Numerical data summarizing the key findings (e.g., moment capacities, degrees of composite action, ACI compliance) have been included at the end of the abstract.

Comment 3:
In the introduction of this study, it should be highlighted that, in addition to traditional 3- or 4-point bending tests and finite element analyses used to obtain load-deflection curves, machine learning methods have also proven to be highly successful thanks to advancements in AI. References to several related studies, as presented below, should be included to support this point.

Response:
I have added a paragraph in the Introduction section that discusses the recent integration of machine learning in structural engineering and references several related studies, including those listed by the reviewer.

Comment 4:
The panel details presented in Figure 2 are not clearly readable. The visuals should be enlarged and made more easily understandable.

Response:
Figure 2 has been revised with enlarged text and clearer panel details to improve readability.

Comment 5:
In Figure 4, it is observed that the metal plates used to apply the load in the four-point bending tests do not extend through the full thickness of the panels and therefore only affect the areas they are in direct contact with. This situation negatively impacts the fundamental principle of the four-point bending test. How do you justify that the tests conducted under these conditions accurately represent real-world behavior?

Response:
A detailed justification has been added to Section 2.4, explaining that the partial-depth plates simulate realistic localized loading conditions found in floor slab applications. Additionally, the setup did not lead to localized crushing or non-flexural failures, and flexural behavior was clearly observed.

Comment 6:
Why is Figure 5 unnecessarily large and of low quality? Please revise it.

Response:
Figure 5 has been resized and updated with higher resolution to ensure visual quality and proportionality with the surrounding content.

Comment 7:
The axis labels in Figure 6 should be repositioned and presented with greater attention to detail.

Response:
Axis labels in Figure 6 have been repositioned and reformatted for improved clarity and visual appeal.

Comment 8:
How does testing only one specimen of each panel type ensure the reliability of the study? At least three specimens of each panel type should be tested.

Response:
A paragraph has been added in the Discussion section acknowledging this limitation and explaining that due to practical constraints, only one specimen per panel type was tested. However, consistent trends aligned with theoretical expectations and literature findings provide confidence in the reliability of the results. Future work will include more replicates.

Comment 9:
Reference numbers should be checked to ensure there are no errors.

Response:
All references and their corresponding in-text citations have been cross-checked and corrected where necessary.

Comment 10:
It is recommended to review English grammar and spelling errors.

Response:
The entire manuscript has been thoroughly proofread to correct any grammatical and spelling issues, ensuring a professional academic tone throughout.

 

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

1. Lines 177-181 Previously they were bullet points. Please correct this by arranging them in a way that is easily understood.
2. Figure 2 needs to be referred to in lines 190-193.
3. Line 532-what do you mean by “as the weight was progressively raised”? Do you mean the “load”? Please revise this sentence for clarity.
4. Increase the font sizes-Figures 4 and 5
5. Improve the quality of Figure 7. Remove the boundary. Improve the axis grids and markers. Right now, it does not satisfy the standard of a journal paper.
6. The way you have the ASTM standards in the list of references is wrong. Please correct them.

Author Response

1. Lines 177-181 Previously they were bullet points. Please correct this by arranging them in a way that is easily understood.

Response:
These lines have been arranged using bulleted points for better understanding.

1. Figure 2 needs to be referred to in lines 190-193.

 

Response:

Figure 2 has already been referred in these lines.

 

1. Line 532-what do you mean by “as the weight was progressively raised”? Do you mean the “load”? Please revise this sentence for clarity.

 

Response:
Yes, here the weight means load. However, I have changed the word in the paper for clarification.

 

1. Increase the font sizes-Figures 4 and 5

 

Response:
Figures have been revised to have an increased font size.

 

1. Improve the quality of Figure 7. Remove the boundary. Improve the axis grids and markers. Right now, it does not satisfy the standard of a journal paper.

 

Response:
I have improved the quality of figure as said.

 

1. The way you have the ASTM standards in the list of references is wrong. Please correct them.

 

Response:

I have corrected the reference of ASTM Standards.

Reviewer 3 Report

Comments and Suggestions for Authors

It appears that the previously indicated revision points have not been fully addressed. In particular, I had emphasized that at least three tests should be conducted for each specimen; however, this requirement has not been considered. The explanation that “Future work will include more replicates.” is inadequate and inconsistent. From a scientific standpoint, in order to establish a reliable finding, a minimum of three tests should be performed, yielding closely aligned and consistent results. This aspect constitutes the most important and critical part of the manuscript. Furthermore, among the recommended references related to machine learning (ML), only one has been included. This is insufficient for studies concerning this methodology; the number of references should be increased, and it would be appropriate to incorporate the full suggested list.

Author Response

For both steel and concrete, three specimens were prepared and tested in accordance with standard practice, ensuring the statistical reliability of the results. In the case of SCIP specimens, however, conducting three full-scale tests for each configuration is not feasible due to the considerable cost, scale, and logistical constraints associated with their fabrication and testing. To mitigate this limitation, rigorous preparation, strict quality control, and detailed measurements were implemented to ensure that the results are representative and reliable. This distinction has now been explicitly stated in the revised manuscript to emphasize that the replication requirement was fulfilled for steel and concrete, while the practical limitations of SCIP testing have been carefully acknowledged. Additionally, I have now incorporated the full list of suggested ML references and enriched the discussion to strengthen the methodological and scientific context of our work.

Round 3

Reviewer 3 Report

Comments and Suggestions for Authors

It is a well-recognized fact among researchers that generalizations cannot be made based on the analysis of a single sample, and that even consistent results obtained from only one sample are not sufficient to provide adequate validation of its suitability. For these reasons, I have reached the decision to reject the manuscript in its current form.