Feasibility of the Maturity Concept for Strength Prediction in Geopolymer Based Materials

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study investigated the compressive strength development of geopolymer mortar made from FA and GGBFS under different curing conditions. A predictive model was developed, providing a reliable tool for predicting the strength of geopolymer under different curing conditions and offering valuable insights for optimizing the formulation of geopolymer concrete. However, there are still significant issues to be addressed in this study, and my specific comments are as follows:

1. Table 1 provides the chemical compositions of FA and GGBFS, but it lacks key physical parameters (such as specific surface area and particle size distribution).
2. Curing FA-based samples at 120°C may cause rapid evaporation of water, leading to microcracks.
3. In the multivariate model established by formulas (4) and (5), parameters such as CaO content and silica-to-alumina ratio were not reflected in the experimental design
4. Lack of comparative analysis with classic literature. It is necessary to systematically elaborate on the specific improvements and advantages of the model presented in this paper compared to traditional methods
5. The validation of the model's predictive validity is insufficient. The author needs to provide the predictive accuracy of the proposed predictive model for the experimental results of existing studies.

Author Response

Comments 1: Table 1 provides the chemical compositions of FA and GGBFS, but it lacks key physical parameters (such as specific surface area and particle size distribution).

Response 1: We agree with this observation, but the particle size distribution and specific surface area for both fly ash and GGBFS could not be measured at this time due to a lack of appropriate testing equipment. Furthermore, we were celebrating religious holidays, so all offices and laboratories were closed. As a result, we didn't have enough time to finish the testing. I wrote the assistant editor to seek an additional two weeks of extension, but we have not heard back yet.

Comments 2: Curing FA-based samples at 120°C may cause rapid evaporation of water, leading to microcracks.

Response 2: We agree with this statement. However, no microcracks were discovered. This is probably due to the usage of Class F fly ash, which has a lower calcium concentration and slow reaction. The microstructure probably gets denser after heat curing. Additionally the samples were heated to 120°C with a gradual rate to reduce the possibility of cracking caused by thermal stresses.

Comments 3: In the multivariate model established by formulas (4) and (5), parameters such as CaO content and silica-to-alumina ratio were not reflected in the experimental design.

Response 3: We appreciate your remark; nonetheless, the main goal of this work is to find how temperature and curing time affect the strength growth of geopolymer mortar or concrete. To enable a meaningful comparison between our experimental compressive strength results and previous studies on geopolymer-based products, the ultimate strength had to be included. This ultimate compressive strength was predicted based on the most influential parameters—namely, the CaO content and the silica-to-alumina ratio—which are known to significantly affect geopolymer performance and are reflected in Formula 5. This formula can be further developed to include additional influential parameters as more data becomes available. However, within the scope of this study, the focus remained specifically on curing time and temperature, which are the key parameters related to material maturity.

Comments 4: Lack of comparative analysis with classic literature. It is necessary to systematically elaborate on the specific improvements and advantages of the model presented in this paper compared to traditional methods

Response 4: I liked to do this comparison. Although all the available and existing models predict the strength development of concrete with age and modified with maturity concept using the equivalent age (temperature-adjusted time) but all these available models are for conventional Portland cement concrete and I could not apply my model to Conventional cement concrete because in formula 7, ultimate strength is function of the parameters related to Geopolymer products only.

Comments 5: The validation of the model's predictive validity is insufficient. The author needs to provide the predictive accuracy of the proposed predictive model for the experimental results of existing studies.

Response 5: I collected 72 data points from the previous existing  studies. shows the relationship between the compressive strength of geopolymer concrete predicted versus observed. The accuracy of the proposed model was evaluated using statistical measures, including the coefficient of determination (R²) and a sum of squared error. The correlation between equivalent age and strength for FA-based geopolymer based products yields a coefficient of determination R²₌ 0.77, a Sum of Squared Errors (SSE) of 5535,  

 

Reviewer 2 Report

Comments and Suggestions for Authors

In this study, the objective is to predict the compressive strength of geopolymer concrete under various curing conditions. This study investigates the compressive strength development of geopolymer mortar made from fly ash and ground granulated blast-furnace slag under varying curing conditions. Based on the maturity concept, incorporating experimental data and best-fit analysis, the accurate strength prediction equation was proposed.

 This paper conforms to the concept of sustainable development and has certain engineering significance. However, the depth of the research is slightly insufficient. The deficiencies existing in the manuscript still need to be further improved.

1. Generally speaking, the research objective is very important. In the abstract, the research objective is not clear. It is suggested to supplement it.
2. The key words "geopolymer concrete" and "geopolymer mortar" are repeated. It is suggested to list geopolymer separately.
3. Abbreviations that first appear in the main text of the manuscript should be marked with their full names at the beginning. For example, in line 36 of the introduction: "GGBFS", and in line 45: "NBS".
4. The parentheses for the references in the manuscript are inconsistent. It is suggested that they be corrected. For example, "(1)", "[2,3]", "[21,22]".
5. The second paragraph of the introduction states: "coefficients's' and activation energy (E)". This makes it difficult for readers to understand. It is suggested that the expression of this equation be given before this statement.
6. In the introduction, the analysis of the existing research is slightly insufficient. It is suggested to enrich the review of the existing related research.
7. Section 2 of the manuscript is "Materials and Methods". In Paragraph 1 of this section, it is expressed as:  “The Materials and Methods should be described The major goal of the experimental work done for this research is to  prepare and test geopolymer mortar utilizing FA and GGBFS as alumina and silica sources. This expression is not clear.
8. The raw materials used in the test were FA and GGBFS. Its particle size has a significant impact on the performance of geopolymer concrete. It is recommended to provide its detailed particle gradation in a
9. Table 2 provides mix proportions of the g It is suggested to further describe the basis for adopting the mix proportions.
10. Table (3) shows the best fit parameters. The title and serial number in Table 3 are missing and need to be supplemented.
11. The conclusion of the manuscript should be further condensed and the content of future prospects should be added.

Comments on the Quality of English Language

The English could be improved to more clearly express the research.

Author Response

Comment 1: Generally speaking, the research objective is very important. In the abstract, the research objective is not clear. It is suggested to supplement it.

Response 1: We agree with this comment, the objective of the study added to the abstract and highlighted in red

Comment 2: The key words "geopolymer concrete" and "geopolymer mortar" are repeated. It is suggested to list geopolymer separately.

Response 2: Geopolymer , concrete and mortar listed separately

Comment 3: Abbreviations that first appear in the main text of the manuscript should be marked with their full names at the beginning. For example, in line 36 of the introduction: "GGBFS", and in line 45: "NBS".

Response 3: Thank you for this comment. Both abbreviation GGBFS and NBS marked with their full names 

Comment 4: The parentheses for the references in the manuscript are inconsistent. It is suggested that they be corrected. For example, "(1)", "[2,3]", "[21,22]".

Response 4: I Agree to this comment.  All parenthesis of the references are corrected 

Comment 5: The second paragraph of the introduction states: "coefficients's' and activation energy (E)". This makes it difficult for readers to understand. It is suggested that the expression of this equation be given before this statement.

Response 5: I agree with this comment ,. The equation of fib Model Code 2010 given before the coefficient "S"   

Comment 6: In the introduction, the analysis of the existing research is slightly insufficient. It is suggested to enrich the review of the existing related research.

respionse 6: I agree with this comment. The fib Model Code, which forecasts how concrete strength develops with age, is included in the Introduction. In addition, the temperature-adjusted age has been added to change the model based on the maturity idea. It has been proven that the parameters S and E are dependent on the cement type, as well as the type and content of supplemental cementitious materials (SCMs); hence, in this work, they are also dependent on the binder type, which is geopolymer rather than ordinary cement.

Comment 7: Section 2 of the manuscript is "Materials and Methods". In Paragraph 1 of this section, it is expressed as:  “The Materials and Methods should be described The major goal of the experimental work done for this research is to  prepare and test geopolymer mortar utilizing FA and GGBFS as alumina and silica sources. This expression is not clear.

Response 7: I agree to this comment , the paragraph is corrected

Comment 8: The raw materials used in the test were FA and GGBFS. Its particle size has a significant impact on the performance of geopolymer concrete. It is recommended to provide its detailed particle gradation in a

Response 8: I agree with this comment. The specific surface area and particle size distribution of both fly ash and GGBFS could not be determined due to the unavailability of the required equipment in our laboratory. Additionally, as these days coincided with our religious holidays, during which all governmental and private offices and laboratories were closed, we did not have sufficient time to conduct these tests. I had also sent an email to the Assistant Editor requesting a two-week extension to perform the tests; however, I have not yet received any response.

Comment 9: Table 2 provides mix proportions of the g It is suggested to further describe the basis for adopting the mix proportions.

reasponse 9 : The bases for the mix proportion added in lines 304 to 318 highlighted in red

Comment 10 : Table (3) shows the best fit parameters. The title and serial number in Table 3 are missing and need to be supplemented.

Response 10: Thank you for this comment , The title and table number added

Comment 11 : The conclusion of the manuscript should be further condensed and the content of future prospects should be added.

Response 11: Agree to the comment; the conclusion condensed, and a short forward-looking statement is added.

Reviewer 3 Report

Comments and Suggestions for Authors

    This study investigates the development of compressive strength in a geopolymer mortar prepared by activating fly ash and ground granulated blast furnace slag using an alkaline solution of NaSiO₃/NaOH. The authors cast specimens following ASTM C109 standards, using a binder/sand ratio of 1:2.75, and compacted them for full densification. Additionally, they developed a predictive model for geopolymer concrete prepared with an alkali-to-binder ratio of 0.45 and a NaOH molarity of 12. This model showed high accuracy, offering a reliable tool for predicting the strength of geopolymers under various curing conditions and providing valuable insights for optimizing geopolymer concrete formulations. I find that the development of a computational model for predicting geopolymer strength is an innovative approach. The manuscript is also clear and well-organized. I suggest it be accepted for publication after major revisions.

The following comments aim to improve the quality of the manuscript:

- For clarity, “2.1 Materials” in the Materials and Methods section must be changed to “2.1 Raw Materials”.

- The unit of chemical composition presented in Table 1 is missing. If this composition was determined by XRF, the sum of oxides and LOI must be 100 %. The technique used must be described.

- The author should provide a flowchart summarizing all preparation steps.

- The particle size distribution analysis and compressive strength measurements are not described in the experimental section.

- The author should provide the standard deviation for the relevant experimental data.

- Please review the legends within Figures 1 and 2 (e.g. T=40C).

- The caption for the table on page 11 is missing.

Author Response

Comments 1: For clarity, “2.1 Materials” in the Materials and Methods section must be changed to “2.1 Raw Materials”.

Response 1: Agree, Material changed to raw material

Comments 2: The particle size distribution analysis and compressive strength measurements are not described in the experimental section.

Response 2: Particle size distribution and compressive strength measurements are described

Comment 3: The author should provide the standard deviation for the relevant experimental data.

Response 3:  The standard deviation is added in figures 3 and figure 4 by using error bar plot on the data series

Comment 4: Please review the legends within Figures 1 and 2 (e.g. T=40C).

Response 4: Agree to this comment , all legends in figure 1 and 2 are corrected.

Comment 5 : The caption for the table on page 11 is missing.

Response 5 : The caption added to the table 3 on page 11 

Reviewer 4 Report

Comments and Suggestions for Authors

Dear authors,

the subject of your work is interesting but I have some coments:

• please verify all your scintific notation (Na2SiO3 or Na₂SiO₃ and others)
• please verify how you yse the measurements units (5°C - 5 °C)
• first of all is very important how you present your work (scientifically)
• you have a lot of errors - see at least line 98, 99, 171-174
• Table 1 - which are the measurement units
• Please review the caption of your figures
• Please decribe the used equipments
• Please verify all yours figures. You have a lot of errors

 

Author Response

Comments 1: please verify all your scintific notation (Na2SiO3 or Na₂SiO₃ and others)

Response 1: Agree , all scientific notations are unified became Na₂SiO₃ 

Comments 2: please verify how you yse the measurements units (5°C - 5 °C)

Response 2: All measurment units unified ( 5°C)

Comments 3: first of all is very important how you present your work (scientifically) you have a lot of errors - see at least line 98, 99, 171-174

Response 3: All lines checked and reviewed 

Comments 4 : Table 1 - which are the measurement units

Response 4: Measurment unit added to table -1 (%)

Comments 5:Please review the caption of your figures

Response 5: Caption of all figures are reviewed.

 Comments 6 : Please describe the used equipment.

Response 6: Agree , All the used equipment are described in the text.

Comments 7: Please verify all yours figures. You have a lot of errors

Response 7: Thanks for the comment , All figure are verified. 

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have made great efforts to improve the quality of the manuscript, therefore it is recommended that the manuscript be accepted.

Author Response

Comments 1:The authors have made great efforts to improve the quality of the manuscript, therefore it is recommended that the manuscript be accepted.

Response 1: Thank you very much for your comment .

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have implemented all the recommended revisions. The manuscript is now suitable for acceptance and publication in J.Compos.Sci. 

Author Response

Comments 1: The authors have implemented all the recommended revisions. The manuscript is now suitable for acceptance and publication in J.Compos.Sci. 

Response: Thank you very much for your comment.

Reviewer 4 Report

Comments and Suggestions for Authors

Dear authors,

you still have some errors:

- °C-hours (or °C-days) - ???

- 4.75 mmm - ?

- please enhance the quality of figure 2, 9, 10

 

Author Response

Comments 1: - °C-hours (or °C-days) - ???

Response 1:  Agree with this remark; this is the unit of the maturity index, appropriately enclosed in quotation marks, similar to other units.

Comments 2: - 4.75 mmm - ?

Response 2: Thanks. Corrected in line number 253

Comments 3: - please enhance the quality of figure 2, 9, 10

Response 3:  Thank you. Figures (9,10) were generated by executing a program written in Python. The initial quality of the images was satisfactory; however, I altered the dimensions by elongating the horizontal axis, which caused the text to seem stretched in the x-direction. I adjusted the length-to-width ratio to its original state. In Figure 2, I have also adjusted the size, since I determined that this is the most suitable image to provide here.