Hydration Heat Effect and Temperature Control Measures of Long-Span U-Shaped Aqueducts

Response to Reviewer 1 Comments

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

Comments 1: The authors report that they used galvanized stainless-steel tubes. Galvanizing stainless steel is rather unusual and it is possible only for specific classes of stainless steel. I suggest to the authors to check this issue

Response 1: Thank you for pointing this out. We would like to clarify the following points: In the aqueduct pouring project, the cooling pipe needs to be in a humid concrete environment for a long time, and it will also be potentially eroded by the chemical substances of cooling water. Although stainless steel itself has certain corrosion resistance, local corrosion may still occur in a specific complex environment. The galvanized layer can provide additional protection for the stainless steel pipe, forming a dense barrier on the surface of the pipe body, effectively blocking the contact of water, oxygen and various corrosive ions ( such as chloride ions ) with the stainless steel substrate, significantly improving the corrosion resistance life of the cooling pipe in the service environment of the aqueduct, and reducing the failure risk of the cooling system caused by the corrosion damage of the pipeline, so as to ensure that the cooling system plays a stable role in the temperature control during the pouring process of the aqueduct.

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

Comments 1: Abstract 1--Lacks specific numerical values or ranges for stress beyond mentioning exceedance of allowable limits.

Response 1: Thank you for pointing this out. We agree with this comment. Therefore, we have supplemented the key stress value range in the abstract, clearly pointing out the specific maximum stress value, and the proportion of these values beyond the allowable limit of the specification to make the results more specific and clearer. – page number 1, paragraph 1, and line 19 to 21.

“[The maximum tensile stress reaches 6.37 MPa, exceeding the allowable value of the tensile strength of the current concrete (1.85 MPa) by 244%]”

Comments 2: Abstract 2--The “Mitigation Strategy Proposal” is briefly stated without highlighting novelty or comparison to existing methods.

Response 2: We have supplemented and highlighted the advantages and innovations of the pipeline cooling system scheme proposed in this study with existing methods in terms of efficiency, applicability or cost. – page number 1, paragraph 1, and line 21 to 31.

“[compared to single-layer systems, the proposed mid-depth double-layer steel pipe cooling system (1.2 m/s flow) reduced peak temperature by 23.8°C and improved cooling efficiency by 28.7%. The optimized water circulation maintained thermal balance between concrete and cooling water, achieving water savings and cost reduction while ensuring structural quality.]”

Comments 3: Abstract 3--No mention of the limitations of the proposed cooling system or potential areas for further research.

Response 3: We have added a description of the limitations of the proposed cooling system (such as applicable environment, energy consumption, construction difficulty, etc. ) , and proposed future research directions.– page number 1, paragraph 1, and line 31 to 34.

“[(5) The cooling system proposed in this paper has certain limitations in terms of applicable environment and construction difficulty. Future research can combine BIM system to dynamically control the tube cooling system in real time.]”

Comments 4: Introduction 1--Overemphasis on literature without identifying a clear knowledge gap.

Response 4: We have modified the introduction section to highlight the existing research on multi-focus conventional structural forms of aqueducts, but there is a lack of systematic research on the hydration heat effect of large-span U-shaped thin-walled structures. It is clearly pointed out that similar temperature control failure leads to structural cracks, which highlights the engineering urgency of this study– page number 1, paragraph 2, and line 41 to 43.

“[The existing research focuses on the hydration heat temperature control measures of conventional cross-section aqueducts [1-4]. Previous studies on these U-shaped aqueducts have primarily concentrated on structural optimization design [5-7], seismic performance [8-10], and dynamic fluid-structure interaction [11-12] and less attention has been paid to the temperature field and stress field caused by hydration reaction during concrete pouring.]”

Comments 5: Introduction 2--Redundant information (e.g., rephrased explanation of temperature gradient issues).

Response 5: Thank you for pointing this out. We agree with this comment. Therefore, we have streamlined the problems caused by temperature gradient, avoided repeated elaboration, ensured that the problem description is concise and clear, and improved the fluency of article reading.

Comments 6: Introduction 3--Fails to clearly state what makes long-span U-shaped aqueducts more challenging compared to similar structures.

Response 6: We have supplemented and analyzed the special challenges of large-span U-shaped aqueducts compared to other types of aqueducts (such as rectangular, T-shaped, etc.) in terms of structural stress, temperature control complexity, and construction difficulty, and specifically explained the control problems caused by the characteristics of larger spans, thin-walled structures, and high stress concentration– page number 2, paragraph 2, and line 60 to 72.

“[The thermodynamic behavior of U-shaped aqueduct is more complicated than that of rectangular / box-shaped aqueduct due to its special geometric shape ( the bot-tom is circular and thick to bear bending moment, and the side wall becomes thinner upwards ) : the large amount of cement in the thick bottom area, the concentration of hydration heat and the difficulty of heat dissipation lead to the high core temperature ; the thin side wall has fast heat dissipation and low temperature, and the huge temperature difference between the inside and outside and the cross section causes temperature stress, which significantly increases the risk of cracking. At the same time, the U-shaped groove bottom plate and the side wall form a strong integral shell structure through a smooth transition of continuous arc surface, and each part is strongly con-strained by each other during temperature deformation. The rectangular / box aque-duct bottom plate and the side wall are mostly right-angled connections, the constraint complexity and continuity are low, and the temperature stress control is relatively easier.]”

Comments 7: Introduction 4--No mention of real-world case failures or cracking incidences that prompted this research.

Response 7: We have introduced typical cases of temperature cracks in large-span aqueducts in related fields in recent years to illustrate the realistic background and needs of this study– page number 2, paragraph 2, and line 72 to 77.]

“[Due to the excessive internal and external temperature difference and too fast cooling rate during the construction period, as well as the strong constraint at the intermittent surface, the concrete of the side wall of the Shahe Aqueduct generates excessive horizontal temperature tensile stress on its inner surface, and the inner side of the side wall cracks, which poses a certain threat to the safe operation of the aqueduct [16]. This project case highlights the engineering urgency of the analysis of the hydration heat effect of the U-shaped thin-walled aqueduct and the study of temperature control measures.]”

Comments 8: Project Overview 1--Dense technical descriptions lacking visual aids (e.g., actual images or clearer schematics).

Response 8: Thank you for pointing this out. We agree with this comment. Therefore, we have added on-site photos, equipment layout diagrams and clearer and more concise structural diagrams to visually display the location and structural characteristics of the measuring equipment– page number 5, paragraph 3, and line 169 to 172.

Comments 9: Project Overview 2--No justification for sensor layout or explanation of why only the left half was considered.

Response 9: We have added a detailed description of the sensor placement strategy– page number 4, paragraph 1, and line 120 to 136.

Comments 10: Project Overview 3--Absence of information on ambient conditions during monitoring (season, weather variability).

Response 10: We havesupplemented the description of environmental parameters during the monitoring period, such as season, meteorological conditions– page number 5, paragraph 5, and line 173 to 175.

“[The project is located in Nanchong City, Sichuan Province. The concrete pouring time is April 2024. According to the measured data, the measured temperature of the concrete during the pouring period is 20 °C, and the average wind speed is 3m / s.]”

Comments 11: Project Overview 4--Lacks discussion on why C50 concrete and specific dimensions were selected.

Response 11: We have described the basis for the selection of C50 concrete and structural dimensions– page number 3, paragraph 1, and line 93 to 103.

“[Based on the structural bearing and durability requirements, C50 concrete is selected for the aqueduct body, and its 28-d cube compressive strength can meet the bearing requirements under the combined action of prestressed system, self-weight and water load. The durability design of impermeability grade P8 is adapted to the long-term water environment service characteristics of the aqueduct. The size design is verified by multi-objective optimization. The groove width and groove depth parameters en-sure the uniformity of flow velocity under the design flow rate through hydraulic calculation. The stability of the 0.35 m thin-walled side wall under the action of water pressure is verified by finite element analysis. The thickening area of the 1 m bottom plate is oriented to strengthen the bending moment concentration characteristics of the bearing. All structural dimensions are demonstrated by the special demonstration of structural bearing capacity to achieve the balance between hydraulic performance and structural safety.]”

Comments 12: Finite Element Simulation Analysis 1--Modeling assumptions overly simplistic: e.g., assuming homogeneous, isotropic concrete and neglecting steel reinforcement effects.

Response 12: Thank you for pointing this out. We would like to clarify the following points: The core of this paper lies in combining field measurements with finite element simulations to analyze the temperature history (including peak temperature, temperature differentials, and cooling rates) of an aqueduct and the resulting thermal stresses. Subsequently, temperature control measures are proposed. The hydration heat temperature field and stress field are primarily governed by the average thermal properties of the concrete, the structural geometry, and the boundary constraints. Crucially, during the critical hydration heat release period, effective bonding between the concrete and reinforcement has not yet fully developed. Consequently, the reinforcement barely participates in bearing loads and does not contribute significantly to the generation of early-age thermal stresses. At this stage, the stresses are predominantly induced by the thermal expansion of the concrete itself and external restraints. Therefore, the simplified model presented in this paper is well-suited for analyzing early-age hydration heat effects. For predicting later-stage mechanical behavior or investigating localized effects (such as in densely reinforced zones), more refined models become necessary.

Comments 13: Finite Element Simulation Analysis 2--Constant thermal parameters might not reflect real hydration behavior.

Response 13: Thank you for pointing this out. We would like to clarify the following points: This paper adopts constant thermal parameters based on the following rationale:

1、Model simplification and efficiency improvement: Hydration heat analysis (especially for large structures or complex models) involves enormous computational effort. Setting thermal parameters as constant values can significantly simplify the calculation process and improve computational efficiency.

2、Feasibility of parameter acquisition: Precisely determining the functional relationships of thermal parameters with hydration degree and temperature is highly challenging, requiring complex experimental equipment and methods. For conventional engineering projects, obtaining a reliable set of constant parameter values through experiments or by referencing codes and standards is considerably easier and less costly than acquiring a complex variable-parameter function.

3、Usability of results: In the vast majority of engineering applications (such as predicting the peak temperature rise of mass concrete, internal-external temperature differences, cooling rates, and assessing cracking risks), the temperature field distribution, temperature rise curves, and key characteristic values (e.g., maximum temperature, maximum internal-external temperature difference) obtained using a constant thermal parameter model generally provide sufficient engineering accuracy. This accuracy meets the requirements for guiding temperature control measures (such as cooling pipe arrangement, insulation layer design, and control of lift/pour thickness).

Comments 14: Finite Element Simulation Analysis 3--Lacks a sensitivity analysis to examine how parameter variations affect the simulation.

Response 14: Thank you for pointing this out. We would like to clarify the following points: The core objective of this study is to reveal the variation laws of hydration heat temperature fields and stress fields in aqueducts through comparing simulation and measured data, and to propose water cooling optimization measures. During model construction, parameter selection was consistently benchmarked against engineering measured data and specification requirements: parameters like initial pouring temperature and ambient temperature in the simulation were directly derived from real-time construction monitoring data to ensure alignment with actual conditions; comparisons between measured data from different pouring sections and construction periods of the aqueduct and simulation results showed good agreement, with small temperature peak deviations and consistent stress trends, reflecting the model’s adaptability to common engineering parameter fluctuations (e.g., slight ambient temperature changes and pouring batch differences) to a certain extent. Sensitivity analysis has been included in subsequent research plans, which will focus on key parameters of aqueduct hydration heat simulation (such as adiabatic temperature rise rate and cooling water flow rate) to clarify the impact of critical parameter fluctuation thresholds on temperature control effectiveness, with relevant results to be elaborated in subsequent papers.

Comments 15: Finite Element Simulation Analysis 4--No error quantification method between measured and simulated values.

Response 15: Thank you for pointing this out. We would like to clarify the following points: We have given the measured and simulated absolute errors of the temperature peak and the time of the temperature peak. As for the stress comparison, it is difficult to directly quantify the absolute error like the temperature due to the limitation of data discreteness and the complexity of stress monitoring. However, the trend consistency verification has been illustrated in the paper.

Comments 16: Analysis of Measured Results 1--Limited discussion of uncertainty or instrumentation errors.

Response 16: Thank you for pointing this out. We have supplemented the accuracy and range of the instrument to increase the rigor of the analysis. – page number 8, paragraph 1, and line 247 to 251.

“[The range of the temperature element of the resistance type temperature element selected in this test is -30 ~ 70°C, and the accuracy is ± 0.5°C. Under the environment of 25°C, the temperature measurement error is not more than 0.3°C, and the temperature element is installed with protective measures, which can meet the requirements of data acquisition and storage for more than 20 days of continuous testing.]”

Comments 17: Analysis of Measured Results 2--Plots are visually overwhelming with insufficient interpretation in the text.

Response 17: Thank you for pointing this out. We would like to clarify the following points: These charts (a-f) are the hydration heat temperature time history curves of different regions and different numbered measuring points (such as T1-X, T2-X series) of the aqueduct, which are used to visually show the temperature change law of concrete in different positions during the hydration process. We fully understand the ' visual complexity ' issue you mentioned, which is due to the complex structure of the aqueduct and the large number of measuring points (it is necessary to cover different locations to verify the temperature field distribution), but this also reflects the complexity of engineering practice. In the original text, although each subgraph is not interpreted point-by-point in detail, the core logic has been illustrated by the overall trend.

Comments 18: Analysis of Measured Results 3--Does not address the impact of the deviation between simulated and measured temperature/stress on structural safety decisions.

Response 18: Thank you for pointing this out. We would like to clarify the following points: The measured and simulated temperature deviation (1.0 ~ 8.5°C) and stress trend are consistent, which do not break through the engineering safety control threshold (temperature gradient, tensile strength). From the perspective of safety decision-making, the deviation does not change the core conclusion that the temperature field in the hydration heat stage of the aqueduct needs to control the internal and external temperature difference, and the stress field needs to avoid the tensile stress exceeding the limit. The identification of the “risk area (such as the center of the bottom plate and the thick part) “ by the simulation model is consistent with the actual measurement, which verifies the engineering rationality of the “water cooling optimization measures for the high-risk area”.

Comments 19: Analysis of Measured Results 4--Missing analysis of environmental factors influencing temperature (e.g., wind, solar radiation).

Response 19: Thank you for pointing this out. We would like to clarify the following points: The paper has mentioned the ambient wind speed ( 3m / s ) during the pouring period in the “2.Project Overview”, and calculated the influence of wind speed on the surface convection coefficient ( β = 61.68kJ / (m²·h·°C) ) through the formula (2) in Section 3.3, which has been included in the simulation; because the pouring time is April 2024, the solar radiation intensity is low, and the reflection effect of the steel formwork on the radiation is significant, which has little effect on the temperature field, so it is not discussed emphatically.

Comments 20: Optimization Analysis of Pipe Cooling System 1--Cooling pipe simulation lacks consideration of thermal resistance of pipe materials and transient flow conditions.

Response 20: Thank you for pointing this out. We would like to clarify the following points: In FEA modeling of concrete cooling pipes, neglecting the pipe's own thermal resistance (including pipe wall conduction and internal convective resistance) and the transient nature of water flow is primarily based on the following core reasons:

1、Dominant Thermal Resistance: The conductive thermal resistance of the concrete itself is significantly greater than both the conductive resistance of the thin-walled metal pipe and the convective resistance of the high-velocity forced water flow. Consequently, the primary temperature gradient occurs within the concrete mass, and the temperature difference across the pipe wall is negligible. Neglecting its thermal resistance has minimal impact on the prediction of the overall concrete temperature field.

2、Time-Scale Separation: The concrete hydration temperature rise/cooling process is slow (on the order of hours/days), while the water flow inside the pipe is fast-responding (on the order of seconds/minutes) due to its high velocity. For models focused on the long-term temperature evolution of concrete, the water flow can be considered to reach a steady state instantaneously within each computational time step, and its transient fluctuations can be neglected.

3、Engineering Efficiency and Purpose: The core objective of the modeling is to predict the concrete's peak temperature, temperature gradients, and cooling rate for cracking control. This simplification avoids the substantial computational cost associated with simulating thin pipe walls and complex fluid dynamics, and validations have shown it provides sufficient accuracy for engineering requirements. The commonly used equivalent heat sink method inherently incorporates these simplifying assumptions.

Comments 21: Optimization Analysis of Pipe Cooling System 2--Assumes 1D steady-state flow and neglects head loss—oversimplified.

Response 21: Thank you for pointing this out. We would like to clarify the following points: In the FEA modeling for optimization analysis of flume pipe cooling systems, assuming one-dimensional steady-state water flow and neglecting head loss is justified and practically useful for engineering purposes. The primary reasons are as follows:

1、Focus on Temperature/Stress Fields: The core objective of optimizing flume pipe cooling is to control concrete temperature gradients, peak temperatures, and cooling rates to prevent cracking. These parameters primarily depend on:(1) The flow rate of the cooling water (which determines the overall heat exchange capacity).(2) The inlet water temperature and the duration of water circulation. The influence of head loss on the temperature field is negligible and can be omitted.

2、Controllable Engineering Impact of Head Loss:(1) In actual projects, constant flow rate is directly maintained through closed-loop pump control, counteracting the disturbance to flow rate caused by head loss. (2) Flume pipes are typically short and straight (with few bends/valves), meaning head loss constitutes a small fraction of the total pump head.

3、Validity of 1D Flow Assumption: The pipe length-to-diameter ratio is extremely large (length far exceeds diameter). Flow is predominantly axial, making a 1D model sufficiently accurate for describing axial heat transfer without requiring detailed 3D flow field simulation.

Comments 22: Optimization Analysis of Pipe Cooling System 3--No comparison to alternative cooling systems or validation with field data.]

Response 22: Thank you for pointing this out. We would like to clarify the following points: This study focuses on the preliminary simulation verification of the cold-water pipe optimization system. The core goal is to explore the regulation effect of the system on the temperature field and stress field of the aqueduct hydration heat through finite element simulation. At present, the simulation results are only principle verification, and the field verification needs to be improved in combination with engineering pilot projects (such as small-scale test sections). However, this study has indirectly verified the reliability of the model and laid the foundation for subsequent field verification.

Comments 23: Optimization Analysis of Pipe Cooling System 4--Missing economic analysis or practical deployment challenges.

Response 23: Thank you for pointing this out. We would like to clarify the following points:

The focus of the research stage: the current work is in the technical feasibility verification stage ( first answer ' can effectively control temperature ' ), and the economy and deployment challenges belong to the ' project implementation stage ' problem. After verifying the feasibility of the system principle through simulation, this study can be supplemented by specific projects (such as actual construction bidding and cost accounting of aqueducts).

The preposition of key information: Some engineering constraints have been implied in the simulation (such as the arrangement of cold-water pipes to avoid steel-intensive areas). These constraints can indirectly reflect the ' deployment difficulty ' (need to accurately locate and avoid construction interference). However, because it has not entered the actual project landing stage, the discussion of detailed deployment challenges (such as construction accuracy requirements, pipeline maintenance difficulties) lacks ' engineering data support ', so it has not been carried out yet.

Dependence of economic analysis: The economy of the cooling system (such as cost, water saving rate) is highly dependent on specific engineering conditions (such as aqueduct scale, construction period, local water resources cost).

Comments 24: Conclusions 1--Repeats earlier results without reflecting on research limitations or future improvements.

Response 24: Thank you for pointing this out. We agree with this comment. Therefore, we have revised the conclusion part to avoid simple repetition of the text results, added research limitations analysis, and proposed follow-up research recommendations. – page number 19, paragraph 1, and line 486 to 493.

“[During the layered pouring stage, the maximum concrete temperature of the U-shaped aqueduct reached 87.2°C, occurring at 32 hours after pouring. This peak was located at the center of the bottom slab (with a thickness of 1.95 m) in the constant-section beam segment 2.48 m from the beam end of the aqueduct body. For measuring point 7 (bottom slab of the support section), the central temperature was also as high as 83.8°C (measured) and 87.0°C (simulated). Due to the difficulty in dissipating hydration heat in the central area of such large-thickness sections, these regions have become key focus areas for construction temperature control.]”

Comments 25: Conclusions 2--Does not address the scope of generalizability to other aqueduct types or climatic conditions.

Response 25: We have supplemented and discussed the applicability and limitations of the research results in different types of aqueducts and different climatic environments to enhance the broad guiding significance of the paper.– page number 19, paragraph 4, and line 507 to 520.

“[The reference value of this research results for other aqueduct projects needs to be adjusted according to specific scenarios. Regarding differences in aqueduct types, for aqueducts with other cross-sections such as rectangular and trapezoidal ones, due to differences in heat dissipation area and thickness distribution (e.g., rec-tangular aqueducts have more uniform thickness distribution between side walls and bottom slabs), the location of the temperature peak may shift from the "center of thickness" to "sectional abrupt change areas". Thus, targeted optimization of monitoring points is required. In terms of climate conditions, in high-temperature and high-humidity areas, the concrete heat dissipation rate decreases, leading to potentially higher and longer-lasting temperature peaks. Enhanced measures such as water cooling or surface insulation should be implemented. In cold regions, it is necessary to balance the needs of "freezing prevention" and "temperature control" to avoid excessive insulation causing the temperature difference between inner and surface layers to exceed the limit.”

Comments 26: Conclusions 3--No discussion of potential optimization for different concrete grades, cross-sections, or geographical locations.

Response 26: We have modified the content of the conclusion section, discussed the adaptability of this study to different strength grades of concrete and section sizes, and proposed future multi-variable optimization directions.– page number 19 , paragraph 5, and line 521 to 536.

“[Temperature control optimization for different engineering conditions can be carried out from three aspects: Adaptation of concrete grades: High-grade concrete (e.g., C50 and above) has a higher peak hydration heat. It is recommended to use mineral admixtures (fly ash, slag) to replace cement to reduce hydration heat, and adjust the mix proportion to reduce the unit cement dosage. For low-grade concrete (e.g., C30), the focus can be on optimizing the pouring interval to control stress using early strength growth. Optimization of cross-section design: For large-thickness sections (>1.5 m), it is recommended to set heat dissipation holes or embedded cooling pipes to reduce the central temperature through active temperature control. For small-thickness sections (<0.8 m), surface moisture retention should be strengthened to avoid surface cracking caused by abrupt changes in ambient temperature. Adaptation to geographical locations: In high-altitude areas with large day-night temperature differences, temperature-responsive insulation materials (e.g., phase change insulation layers) should be used. In rainy areas, the timing of formwork removal should be optimized to prevent direct rainwater scouring on the surface of high-temperature concrete, which may induce temperature difference stress.]”

Comments 27: Conclusions 4--Fails to propose a framework for decision-making on temperature control in future projects.

Response 27: Thank you for pointing this out. We agree with this comment. Therefore, we have tried to construct a temperature control strategy decision-making framework based on monitoring and simulation, which is convenient for future engineering practice and promotion. – page number 20, paragraph 1, and line 537 to 554.

“[Based on the research results, a temperature control decision-making framework for aqueduct projects is proposed as follows: Identification of key sections: Prioritize locating large-section areas with a thickness >1.5 m (e.g., support bottom slabs, constant-section segments of beam ends). Predict the location of temperature peaks using finite element simulation and arrange multi-layer temperature sensors. Coupling of climate parameters: Collect meteorological data (daily maximum tem-perature, wind speed, humidity) of the project area for more than 5 years before construction, and establish a "climate-heat dissipation rate" correlation model to predict risk periods of temperature drop. Dynamic control indicators: Take "tem-perature difference between inner and surface layers ≤25°C and daily temperature drop rate ≤2.0°C/d" as core thresholds, and formulate hierarchical measures for different stages: strengthen insulation (e.g., covering with flame-retardant quilts) during the temperature rise stage; adopt gradient removal of insulation layers combined with spray moisturizing during the cooling stage; and immediately ac-tivate water cooling when thresholds are exceeded. Coordination of materials and processes: Select the type and dosage of admixtures according to the concrete grade, and optimize the layered pouring thickness and intermittent time based on cross-section size to reduce interlayer temperature difference stress.]”

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

Comments 1: Suggested title (optional): Influence of cement hydration on thermal stress development and temperature control strategies in long span U-shaped aquedact structures.

Response 1: Thank you for pointing this out. We would like to clarify the following points: After careful reading, based on the core logic of the research content, we still want to retain the original title “Hydration Heat Effect and Temperature Control Measures of Long-Span U-shaped Aqueducts“, for the following reasons : The original title uses a concise phrase structure to completely cover the logic of “ research object ( aqueduct ) → core problem ( hydration heat effect ) → solution ( temperature control measures ) “. Readers can quickly capture the full picture of the research by looking at the title alone.]

Comments 2: The provided introduction section never provide and comprehensive literature to highlight the gab study and the target problem and novelty authors achieved. Please re-write this section and cite/discuss more recent studies in this area and related to this study.

Response 2: Thank you for pointing this out. I/We agree with this comment. Therefore, we have re-written the introduction section, discussed the differences between the current research progress and this study, and listed relevant engineering examples to illustrate the engineering urgency of this study. – page number 2, paragraph 3, and line 60 to 79.

“[The thermodynamic behavior of U-shaped aqueduct is more complicated than that of rectangular / box-shaped aqueduct due to its special geometric shape ( the bot-tom is circular and thick to bear bending moment, and the side wall becomes thinner upwards ) : the large amount of cement in the thick bottom area, the concentration of hydration heat and the difficulty of heat dissipation lead to the high core temperature ; the thin side wall has fast heat dissipation and low temperature, and the huge tem-perature difference between the inside and outside and the cross section causes tem-perature stress, which significantly increases the risk of cracking. At the same time, the U-shaped groove bottom plate and the side wall form a strong integral shell structure through a smooth transition of continuous arc surface, and each part is strongly con-strained by each other during temperature deformation. The rectangular / box aque-duct bottom plate and the side wall are mostly right-angled connections, the constraint complexity and continuity are low, and the temperature stress control is relatively easier. Due to the excessive internal and external temperature difference and too fast cooling rate during the construction period, as well as the strong constraint at the in-termittent surface, the concrete of the side wall of the Shahe Aqueduct generates ex-cessive horizontal temperature tensile stress on its inner surface, and the inner side of the side wall cracks, which poses a certain threat to the safe operation of the aqueduct [16]. This project case highlights the engineering urgency of the analysis of the hydra-tion heat effect of the U-shaped thin-walled aqueduct and the study of temperature control measures.]”

Comments 3: Used software version and year as well as the modeling steps should include with more details.

Response 3: We have [supplemented the detailed modeling steps of the finite element model and the software version used. – page number 7, paragraph 7, and line 237 to 244.

“[The U-shaped aqueduct adopts the concrete pouring technology of “staggered from one end to the other end, left and right webs and bottom plates-symmetry-stratified-segmented distribution “. In the Midas / FEA NX 2024 software simulation construction stage division, the U-shaped aqueduct is divided into three construction stages to simulate the pouring of aqueduct concrete. The first stage is to pour 1 / 4 circle, the second stage is to pour a complete semicircle, and the third stage is to pour the vertical section, that is, to complete the pouring (here does not simulate the pull rod ). According to the actual situation of the site, the simulation pouring takes 16 h, 6 h, 2 h.]”

Comments 4: Figures 4, and 11 are very low quality and not clear, please replace this figure with one high resolution.

Response 4: We have replaced images 4 and 11 with higher resolution versions.

Comments 5: Figures 6, 8, and 10 must revise; X and Y title should bold not the numbers.

Response 5: Thank you for pointing this out. We agree with this comment. Therefore, we have modified pictures 6 8 and 10 as required.

Comments 6: Please revise both images of Figure 7a and b!

Response 6: Revised.

Comments 7: Title of sections and sub-sections must follow the journal style.

Response 2: Revised.

Comments 8: Results poorly discussed and not details and reasons for the findings or compared to literature. Please consider that in the revised version.

Response 2: Thank you for pointing this out. We agree with this comment. Therefore, we have re-written our conclusion part. On the basis of combing the original data of the paper, we discuss the reference value of the research results to other aqueduct projects and the temperature control optimization for different engineering conditions, and form a set of temperature control strategies with certain reference value. – page number 19, paragraph 1, and line 486 to 554.

Comments 9: References section should be update.

Response 9: Revised.

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

Comments 1: Given the current climate emergency, it is surprising that the authors have not initiated the paper by addressing this critical issue. It appears that they may not be aware of a pertinent statement made by Professor Pierrehumbert of Physics at the University of Oxford, who unequivocally stated in a 2019 paper, "Let’s get this on the table right away, without mincing words. With regard to the climate crisis, yes, it’s time to panic" (Pierrehumbert, R., 2019, Bulletin of the Atomic Scientists, pp.1-7). In light of the urgency emphasized by such reputable sources, it is imperative that the introduction of the paper establish a direct link between environmental degradation, resource efficiency and concrete durability

Response 1: Thank you for pointing this out. We would like to clarify the following points: Although this study does not directly mention the climate crisis at the beginning of the introduction, there is an intrinsic correlation between the core content and the sustainable development goals :

As a key water conservancy infrastructure, the durability of concrete directly affects the service life of the project. Reducing temperature cracks by optimizing hydration heat temperature control measures (such as water-cooling system in this paper) can reduce the frequency of later maintenance and reinforcement, reduce building material consumption and carbon emissions, and meet the climate adaptation needs of ' resource efficiency improvement '.

The " water-saving water cooling system " (optimizing water circulation to save water) and " long-life structural design " proposed in the study are essentially to reduce resource waste through technical optimization and indirectly respond to the requirements of " green engineering " under the climate crisis.

Comments 2: "The paper offers a compelling and timely contribution to the field, addressing an important topic with evident relevance. However, one critical methodological concern remains unaddressed: the authors do not provide a clear justification for excluding mix composition as a variable in the research design.

Response 2: Thank you for pointing this out. We would like to clarify the following points: The core objective of this study is to analyze the temperature effect of hydration heat and the effectiveness of temperature control measures in the construction stage. The research object is the C50 concrete used in the project (the mix ratio conforms to the ' Hydraulic Concrete Construction Specification ' SL 677-2014). The mix ratio is a set parameter in the material design stage (determined by the engineering design unit based on the bearing capacity and durability requirements), which is not a variable of this study.

If the mix proportion variable is included, it is necessary to carry out additional comparative tests of different mix proportions (such as water-cement ratio and admixture dosage), which is beyond the scope of ' temperature control optimization in construction stage ' in this study.

Comments 3: In addition, the bibliography appears to be composed almost entirely of references authored by Chinese scholars. While these sources may be of high quality, the lack of international representation raises concerns about geographic citation bias — a practice critically examined by Qiu et al. (2025).

Qiu, S., Steinwender, C., & Azoulay, P. (2025). Paper tiger? Chinese science and home bias in citations. Journal of International Economics, 104123

Response 3: Thank you for pointing this out. We would like to clarify the following points: The existing literature selection is mainly based on the following considerations :

Based on the actual aqueduct project in Southwest China, this study focuses on the U-shaped aqueduct, a structural form widely used in China 's water conservancy projects. The references are mostly technical research, normative interpretation and measured data for similar projects, which are highly consistent with the research scenarios.

We agree with the complementary value of international literature, but the current cited literature is enough to support the core conclusions of the study (hydration heat law, effectiveness of temperature control measures). In the revised manuscript, we have added 2 international related studies.