Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this paper, aiming at the limitations of the destructive core-sampling method in the quality control of traditional asphalt pavement, the engineering applicability of the electromagnetic density gauge (EM density gauge) in the density detection of hot asphalt mixture (HMA) is systematically studied. Combined with statistical analysis, the reliability of non-destructive detection technology is verified.

Specific Comments: 

1. Abstract: It is recommended to supplement quantitative results of key data, such as "the density measurement error between the electromagnetic density gauge and the traditional coring method is less than ±2%" or "statistical analysis shows a correlation coefficient of 0.92 within the 95% confidence interval" to enhance the verifiability of the conclusions.
2. Abstract Restructuring: It is suggested to reorganize the abstract following the logical flow of "Research Objective → Methodology → Key Results → Conclusion", avoiding placing statements like "first in Mexico" at the beginning.
3. Keywords: Adjust the keyword order to prioritize "Non-destructive testing" and "Electromagnetic density gauge", and supplement with "Statistical analysis" and "Asphalt mixture durability" to ensure core technologies and methods are highlighted.
4. Introduction Rewriting: The introduction needs to be restructured into a structured narrative, preferably divided into 4–5 paragraphs following the framework of Background, Research Actuality, Research Question, and Research Significance & Innovation. Avoid simple listing of references and ensure proper citation practices.
5. Equipment Description (Line 156): Supplement the electromagnetic density gauge’s model (e.g., PQI 380), measurement range (e.g., density measurement range of 1.8–2.5 g/cm³), and calibration cycle (e.g., weekly calibration) to ensure the methodology is reproducible.
6. Section Division: It is recommended to split the content into distinct Section 2 and Section 3 to enhance structural clarity and readability.
7. Data Collection: Describe on-site testing environmental conditions (e.g., temperature and humidity ranges) and mention outlier removal criteria (e.g., 3σ principle) to improve data reliability.
8. Statistical Tools: Clarify the statistical tools used (e.g., SPSS or Python) and analytical methods (e.g., linear regression, T-test), and supplement specific results of hypothesis testing (e.g., *p* value < 0.05).
9. Conclusion Revision: The conclusion section is too lengthy and needs to be rewritten, paying attention to academic writing structure and methodology.
10. Sample Representativeness (Abstract): The "25.9% representative sample" in the abstract requires an explanation of the calculation logic and a citation of statistical sampling theory (e.g., central limit theorem).
11. Humidity Impact (Table 2): Supplement humidity data in the climatic conditions table (Table 2) and analyze its potential impact on the dielectric constant measurements of EM signals.
12. Table 1 Annotation: The column header "Section ADAT" in the traffic composition table (Table 1) is unclear and should be annotated as "ADAT = Annual Daily Average Traffic".
13. Figures 6–8: Add trend lines and R² values to the density curves, and use polynomial fitting (e.g., quadratic curves) to visually demonstrate density fluctuation patterns across road segments.
14. Calibration Procedure (Lines 156–157, 175–177): The calibration step "average of 5 readings" does not clarify whether it refers to repeated measurements at the same location. It is necessary to specify "5-point regional averaging" to avoid local error misinterpretation.
15. Statistical Test (Lines 290–291): For "standard deviation < 0.030", supplement statistical tests (e.g., F-test) to compare the significance of variance between different JMF groups.
16. Air Voids Standard Conflict (Lines 322–333, 333): Address why "AV = 4% ± 1%" in the manuscript conflicts with the Mexican standard (3–8% mentioned in Lines 74–78). Verify the standard source and explain the rationale for the stricter criteria.
17. Temperature Impact: When discussing the accuracy of the EM density gauge, supplement the pavement temperature range during testing (e.g., 100–150°C) and include a temperature correction formula (e.g., density correction coefficient per 10°C).
18. Core Sampling Location: The statement "at least 3 core extractions per day" does not clarify whether they correspond to EM measurement points. It is necessary to specify that "the spatial error between core points and EM measurement points ≤50 cm" to ensure comparability.
19. Equation Citation: "Equations 1 and 2" are not explicitly mentioned in the main text. Add "as shown in Equations (1) and (2)" in the density calculation section to enhance the scientific rigor of the results and discussion.
20. Figure 7 Title Error: The title "Segment 1" in Figure 7 conflicts with the actual description of "Segment 2". Correct it to "Segment 2" and further check for similar inconsistencies throughout the manuscript.
21. Figure 4 Readability: The text in Figure 4 is too small, affecting readability. Enlarge the font for better clarity.
22. Correlation Analysis (Results & Discussion): The section only qualitatively describes the negative correlation between density and air voids. Quantify this using linear regression (report R² value) and statistical significance tests (e.g., *p* value) instead of relying on qualitative descriptions.
23. Environmental Variable Quantification: Although climatic data (temperature, precipitation) are provided (Table 2, annual average precipitation 814.3 mm), the specific impact of humidity on the dielectric constant measurements of the EM density gauge is not analyzed. Add a "humidity sensitivity analysis" in the discussion section to compare measurement errors under dry and wet conditions (e.g., using pre- and post-rain data to calculate average errors).
24. Technical Comparison with GPR (Lines 127–136): The manuscript mentions that EM costs (US$14,000–21,000) are lower than GPR but only compares costs and operational complexity. Supplement a comparative table of density measurement errors between the two devices at the same measurement points, and evaluate consistency using Bland-Altman analysis.
25. JMF10 Anomaly Attribution (Lines 368–370): The manuscript speculates that the air void non-compliance in JMF10 is due to "insufficient compaction temperature" but provides no construction temperature records or aggregate gradation data, relying solely on standard deviation (σ=0.021). This is logically insufficient and requires supporting data.
26. Sample Screening Criteria: The manuscript mentions "standard deviation < 0.030" without citing the acceptance criterion in AASHTO T343 ("standard deviation ≤0.050 g/cm³"). Compare the manuscript’s criteria with AASHTO standards, explain the rationale for stricter screening (e.g., higher uniformity requirements in Mexico’s rainy environment), and report robustness analysis under relaxed criteria.
27. Aggregate Type Impact: The manuscript does not discuss the impact of different aggregates (e.g., granite with high dielectric constant vs. limestone with low dielectric constant) on EM signals, weakening the conclusion that "aggregate changes affect density readings". Supplement measured dielectric constant data for different aggregates (e.g., granite ε=4.5 vs. limestone ε=3.2) and establish aggregate-type correction factors.
28. Compaction Effort Sensitivity: The manuscript mentions using a gyratory compactor to simulate field conditions but does not analyze the correlation between compaction cycles (e.g., 100 vs. 150 cycles) and EM density readings. Add a "compaction effort sensitivity experiment" in the Materials and Methods section to demonstrate the relationship curve between compaction cycles and EM readings.
29. EM Penetration Depth (Lines 384–388): While GPR signal is affected by thickness, the EM penetration depth is not explained. Cite electromagnetic theory formulas to calculate the EM penetration depth in HMA (e.g., δ=25 mm at 100 MHz) and clarify its limitations for surface layer testing.
30. Policy Recommendation (Conclusion): Propose a recommendation in the conclusion to "incorporate EM density gauges into Mexico’s SCT non-destructive testing standards", supported by field data (e.g., 92% consistency with coring methods).

Author Response

Please see the attachment.

You will find the answers to your comments in this document.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

REVIEWER COMMENTS FOR AUTHORS

The manuscript titled “Statistical analysis as quality validation of hot asphalt mixtures for durability using Electromagnetic Density gauge as a non-destructive method” presents an insightful study on the application of EM density gauges as a non-destructive quality control tool for Hot Mix Asphalt (HMA) in Mexico. The topic is timely and relevant, addressing a key challenge in pavement engineering: achieving reliable field compaction assessment through faster, non-invasive techniques.

The manuscript is methodologically sound, and the statistical treatment of the data is thorough. However, the clarity and precision of the writing could be significantly improved, particularly in the Introduction and Results sections. Some aspects would benefit from further explanation or restructuring to ensure the message is clearly communicated to an international audience.

This manuscript requires minor revisions to improve the language, structure, and contextual background. Below are specific comments and suggestions:

General Comments:

• Language and Grammar: Several sentences are overly long and complex. There are issues with verb tense agreement, article usage, and clarity in phrasing throughout the manuscript. A professional English editing service is recommended.
• Title: Consider simplifying it to something like: “Quality Control of Asphalt Mixes Using EM Density Gauge: A Statistical Evaluation of Field Durability.”
• Novelty and Contribution: Clarify how your findings differ from global literature and cite similar international efforts.
• Figures and Tables: Ensure all figures are referenced in the text and include more descriptive captions.

Specific Comments:

• Lines 13–18 (Abstract): Specify traditional procedures and how the NND method improves them.
• Lines 28–38: Clearly integrate SUPERPAVE’s history with the motivation for using EM gauges.
• Lines 83–89: Clarify the drawbacks of destructive testing, with examples or data.
• Lines 95–100: Include comparative data (e.g., time or cost) for NND vs traditional methods.
• Lines 137–138: Elaborate on training needed for interpreting EM vs GPR readings.
• Lines 184–190: Discuss the trade-offs in using single vs multi-readings for accuracy.
• Lines 243–247: Format equations properly and explain %C and %AV relevance.
• Lines 276–284: Clarify consistency observed and justify method choice.
• Lines 308–310: Add a table summarizing JMF results and statistics.
• Lines 328–334: State if deviations in JMF10 result from construction or equipment issues.

Suggestions for Strengthening the Manuscript:

• Future Work: Consider exploring correlations between real-time EM readings and mechanical performance under traffic loads.
• Policy Implications: Highlight how findings may influence quality control standards in Mexico.
• Comparative Literature: Add discussion on international use of EM and GPR techniques in asphalt QA.

Summary Recommendation:

The manuscript addresses a relevant challenge and provides useful data. After minor revisions for clarity, language, and contextual framing, it will make a strong contribution to the field of pavement engineering and non-destructive testing.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

You will find the answers to your comments in this document.

Thank you very mucho for your comments, they were very useful to improve the paper

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

After major revision, the thesis has significantly improved in terms of data integrity, method standardization and chart quality. The research focuses on the application of electromagnetic densitometer in the quality control of asphalt pavement, which has both engineering value and method innovation. It is suggested to carry out minor repairs to further enhance the rigor.

1.Check if the abbreviation "DNN" in the summary is correct? Check to unify the terms "NND" and "EM density gauge" throughout the text. When it first appears, it is marked with the full name "Non-Nuclear Density Gauge (NND)" or "Electromagnetic Density Gauge (EM)".

2.The consistency between LINE 336-337, "AV=3-8%" and the Mexican standard needs to be further analyzed. When discussing void ratio (AV=3-8%), it is recommended to supplement the quantitative relationship between compaction degree and AV (such as "For every 1% increase in compaction degree, AV decreases by 0.5%"), and refer to the consistency description of Mexican specifications (such as AMAAC 2013).

3.Check and confirm the consistency between the chart numbers and the content of the full text (such as whether the subgraph annotations in Figure 9 correspond to the JMF groups).

4.The conclusion is too long and the structure is not clear. It is suggested that the conclusion section be described point by point as "main findings → Method advantages → Practical suggestions → Future directions", and repetitive content, such as statistical conclusions that are repeated with the previous text, be deleted.

5 Regarding the cover letter:

5.1. In the reply to the quantification results of the abstract (item 1), the author only mentioned "the p-value of the t-student test < 0.05", but did not clarify the error range (such as ±2%) or the correlation coefficient (such as R²=0.92). Suggestion: In the reply, specific values should be supplemented, for example, "Supplementary statistical analysis shows that the measurement error of the EM densitometer and the core-sampling method is ±1.8%, and the correlation coefficient within the 95% confidence interval reaches 0.91", to ensure the verifiability of the data.

5.2 The 13th reply refused to add the trend line on the grounds that "the core data only provides the JMF average value", but did not specify whether the trend could be plotted using the average value (such as piecewise linear fitting), or whether the density fluctuation pattern could be described in words. Suggestion: Change it to "Given that the core data is the average value of JMF, supplement the description of the segmented linear trend in the figure caption, such as' The density of Segment 1 shows an increasing trend of 0.01g /cm³/km with the mileage '" to avoid the loss of chart information.

5.3 The reply to Article 28 deleted the compaction work analysis on the grounds of "reorganizing the introduction", but did not specify whether the experimental design was retained or the discussion was simplified (such as mentioning that "the influence of different compaction works on the density reading is within ±0.02 g/cm³"). Suggestion: Retain a brief description in the material method, such as "Using a comparison of 100/150 rotational compactions, the results show that for every 50 increase in compaction work, the EM density reading increases by 0.03 g/cm³, which is consistent with theoretical expectations", to avoid damaging the integrity of the research.

Author Response

Please see the attachment.

The new article title was suggested by the reviewer 2.

Author Response File: Author Response.pdf