Concrete temperature gradient control method under multi-physics coupling evaluation

Abstract

The present application relates to a kind of concrete temperature gradient control method under the coupling evaluation of multi-physical field, and the concrete sample is prepared based on preset temperature gradient value, and the concrete sample is carried out hydration heat test with the preset temperature gradient value, obtains hydration heat test result;Degree of hydration field is calculated by coupling calculation of hydration model, temperature field is calculated by coupling calculation of heat transfer model, and the evolution of the mechanical properties, shrinkage, creep of concrete is calculated by degree of hydration field, and the evolution of the mechanical properties, shrinkage, creep of concrete and temperature field are calculated together by mechanical model to obtain strain and stress field, and the risk of concrete cracking is analyzed by strain and stress field.The present application solves the technical problems that temperature monitoring point arrangement and monitoring in mass concrete in the prior art are difficult to meet the temperature monitoring requirements.This method reduces the shrinkage of concrete, reduces the shrinkage rate of concrete, avoids the cracking of mass concrete, and further improves the performance of concrete.

Description

Technical Field

[0001] This invention relates to the field of building construction, and in particular to a method for controlling the temperature gradient of concrete under multi-physics field coupling evaluation. Background Technology

[0002] Large-volume concrete structures with a minimum solid dimension of 1m or more, or concrete structures where harmful cracks are expected to occur due to temperature changes and shrinkage caused by the hydration of cementitious materials, are classified as large-volume concrete. Due to the special nature of its construction process, this project features an exceptionally large concrete structure with a thickness exceeding 2m, classifying it as a typical example of large-volume concrete.

[0003] In the technical specifications for temperature monitoring and control of large-volume concrete, when the concrete thickness is uniform, the spacing between measuring points is 10m to 15m. Depending on the thickness of the large-volume concrete, 3-5 measuring points are arranged at each measuring location, situated at the surface, center, bottom layer, and upper and lower middle parts of the concrete. Surface temperature measuring points are placed 50mm from the concrete surface, while bottom layer temperature measuring points are placed 50-100mm above the ground level of the concrete. Data monitoring is required for the highest concrete temperature, surface temperature, surface-to-interior temperature difference, and placement temperature. For structural projects with a concrete thickness greater than 2m, conventional temperature measuring point arrangements and monitoring are insufficient to meet temperature monitoring requirements, easily leading to harmful cracks due to inaccurate temperature measurements. Therefore, a scientific and reasonable temperature monitoring and control method must be provided. Summary of the Invention

[0004] To address the shortcomings of the existing technologies, this invention provides a method for controlling the temperature gradient of concrete under multi-physics field coupling evaluation, which solves the technical problem that the arrangement and monitoring of temperature measurement points in large-volume concrete is difficult to meet the temperature monitoring requirements in the existing technologies.

[0005] This invention discloses a method for controlling the temperature gradient of concrete under multi-physics field coupling evaluation, comprising the following steps:

[0006] S1. Conduct an adiabatic temperature rise test on the concrete to be poured and obtain the test results, then proceed to step S2.

[0007] S2. Prepare concrete samples based on preset temperature gradient values, and conduct hydration heat tests on the concrete samples using the preset temperature gradient values ​​to obtain hydration heat test results, which include hydration heat and hydration rate.

[0008] S3. Calculate the degree of hydration based on the results of the heat of hydration test and compare it with the results of the adiabatic temperature rise test:

[0009] If the degree of hydration and the hydration rate are the same in the two tests, then the preset temperature gradient value is set as the critical value, and then step S4 is executed;

[0010] If the degree of hydration and hydration rate of the two tests are inconsistent, adjust the preset temperature gradient value and return to step S2;

[0011] S4. Prepare concrete according to the material composition of the current concrete sample, and control the pouring temperature through physical methods during concrete pouring. Finally, control the temperature gradient between the surface and the bottom layer below the preset temperature gradient value. Set measuring points at intervals between the surface and the bottom layer, and use the temperature difference between the measuring points of the surface and the bottom layer as the temperature gradient monitoring data.

[0012] The concrete temperature gradient control method under multiphysics field coupling evaluation of the present invention is further improved in that the calculation of the hydration degree field through coupling by the hydration model includes the following steps:

[0013] The degree of hydration is used to describe the extent of hydration of cementitious materials. The degree of hydration is:

[0014]

[0015] Where Q(t) is the heat of hydration as a function of time, Qpot is the heat of complete hydration, and t represents time;

[0016] The hydration rate is:

[0017]

[0018] Where α is the degree of hydration, α max The maximum degree of hydration that the material can achieve, where B1, B2 and η represent the fitting parameters;

[0019] The maximum degree of hydration α that the material can achieve max for:

[0020]

[0021] Wherein SL and FA are the admixture amounts of mineral powder and fly ash, respectively, and Q max ω / c represents the maximum heat release that cement can achieve during hydration, and ω / c represents the maximum degree of hydration of the concrete sample.

[0022] The concrete temperature gradient control method under multiphysics coupling evaluation of this invention is further improved in that, through mechanical model calculation, it includes the following steps:

[0023] The elastic modulus ψ of concrete is calculated using the following formula:

[0024]

[0025] Among them Ψ 28The final value of its performance development after 28 days, where α is the degree of hydration, α0 is the initial value of the degree of hydration, and α... max The maximum degree of hydration that the material can achieve;

[0026] In heat transfer calculations, the boundary condition is a heat flux boundary, and the heat flux q passing perpendicular to the boundary direction is... con for:

[0027] q con =H i ·(T ext -T)

[0028] Where H i Here, T represents the equivalent heat transfer coefficient at different environmental heat transfer boundaries, and T represents the ambient temperature.

[0029] Based on the pouring time and ambient temperature T ext According to the variation of the sine function, the expression is: T ext =27+ksin[2π(x-0.25[d])].

[0030] The concrete temperature gradient control method under multiphysics field coupling evaluation of the present invention is further improved by performing the following steps after step S2 and before step S3:

[0031] The actual concrete pouring process is simulated. The hydration degree field is calculated by coupling the hydration model and the temperature field is calculated by coupling the heat transfer model. The evolution of the mechanical properties, shrinkage, and creep of the concrete is calculated by the hydration degree field. The evolution of the mechanical properties, shrinkage, and creep of the concrete, together with the temperature field, is used to calculate the strain and stress fields through the mechanical model. The risk of concrete cracking is analyzed by the strain and stress fields. The relationship between cracking risk and temperature gradient is analyzed and calculated. It is determined whether the cracking risk corresponding to the preset temperature gradient value exceeds 0.7. If yes, return to step S2; if no, proceed to step S3.

[0032] The method for controlling the concrete temperature gradient under multi-physics field coupling evaluation in this invention is further improved by analyzing the risk of concrete cracking through strain and stress fields: the ratio of the first principal stress to the average tensile strength σ1 / f atm Analysis shows that if the first principal stress is greater than the average tensile strength, the concrete will crack. The crack risk cloud map shows how the overall crack risk of the concrete changes over time.

[0033] The concrete temperature gradient control method under multi-physics field coupling evaluation of the present invention is further improved in that, when setting measuring points at intervals between the surface layer and the bottom layer, measuring points are set at intervals of 600mm on the surface layer and 800mm on the bottom layer.

[0034] Compared with existing technologies, the effects of this invention are positive and significant. This invention, through a multi-physics coupled evaluation method for controlling the temperature gradient of C30 concrete, derives the relationship between cracking risk and temperature gradient, and establishes the location of temperature measurement points along the vertical direction at the center of the concrete plane. This solves the technical problem in existing technologies where the arrangement and monitoring of temperature measurement points in large-volume concrete is insufficient to meet temperature monitoring requirements. This method controls the temperature upon entering the formwork through physical methods such as optimizing the composition of cementitious materials, controlling the temperature of raw materials, cooling during transportation, and wrapping pump pipes with heat-reflective materials at the construction site. Ultimately, it controls the temperature gradient between the surface and the bottom layer below the critical value, achieving the temperature control target to reduce concrete shrinkage, lower the concrete shrinkage rate, prevent cracking in large-volume concrete, and further improve concrete performance. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the calculation process for the concrete temperature gradient control method under multiphysics field coupling evaluation according to the present invention.

[0037] Figure 2 This is a schematic diagram of the generalized Kelvin element for the concrete temperature gradient control method under multiphysics field coupling evaluation according to the present invention.

[0038] Figure 3 This is a schematic diagram of the mesh division for the three-stage pouring of the concrete temperature gradient control method under multi-physics field coupling evaluation according to the present invention.

[0039] Figure 4 The graph shows the ambient air temperature variation function of the concrete temperature gradient control method under multiphysics field coupling evaluation according to the present invention.

[0040] Figure 5 This is a schematic diagram of the displacement boundary conditions for the concrete temperature gradient control method under multiphysics field coupling evaluation according to the present invention.

[0041] Figure 6 This is a schematic diagram showing the changes in temperature gradient and cracking risk along the vertical direction at the center of the plane 14 days after pouring, based on the concrete temperature gradient control method under multi-physics field coupling evaluation of the present invention.

[0042] Figure 7 This is a schematic diagram of the vertical temperature measurement point location in the concrete temperature gradient control method under multi-physics field coupling evaluation according to the present invention. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] During construction, engineers use numerical calculations of the temperature field to investigate the temperature development process and stress generation patterns within large-volume concrete structures to address cracking caused by temperature-induced tensile stress. This provides effective temperature control measures to prevent temperature cracks during construction. In numerical temperature field calculations, parameters such as the heat source function and boundary conditions are typically determined empirically. Finite element method (FEM) software is then used to simulate the entire process of hydration heat generation during concrete pouring, and the corresponding temperature and stress fields are calculated.

[0045] like Figure 1 As shown, this invention provides a method for controlling the temperature gradient of concrete under multi-physics field coupling evaluation, comprising the following steps:

[0046] S1. Conduct an adiabatic temperature rise test on the concrete to be poured and obtain the test results, then proceed to step S2.

[0047] S2. Prepare concrete samples based on preset temperature gradient values, and conduct hydration heat tests on the concrete samples using the preset temperature gradient values ​​to obtain hydration heat test results, which include hydration heat and hydration rate.

[0048] S3. Calculate the degree of hydration based on the results of the heat of hydration test and compare it with the results of the adiabatic temperature rise test:

[0049] If the degree of hydration and the hydration rate are the same in the two tests, then the preset temperature gradient value is set as the critical value, and then step S4 is executed;

[0050] If the degree of hydration and hydration rate of the two tests are inconsistent, adjust the preset temperature gradient value and return to step S2;

[0051] S4. Prepare concrete according to the material composition of the current concrete sample, and control the pouring temperature through physical methods during concrete pouring. Finally, control the temperature gradient between the surface and the bottom layer below the preset temperature gradient value. Set measuring points at intervals between the surface and the bottom layer, and use the temperature difference between the measuring points of the surface and the bottom layer as the temperature gradient monitoring data.

[0052] Adiabatic temperature rise refers to the increase in internal temperature after concrete pouring due to the release of heat from hydration. The temperature rise is measured from the initial temperature at the formwork entry point to the highest temperature. Adiabatic temperature rise tests are conducted to obtain data on the corresponding heat of hydration and hydration rate during this process. In this embodiment, a temperature gradient of 20 K / m is assumed and used in the calculations. This value is then compared with the results of the adiabatic temperature rise test to determine if the temperature gradient is critical. If it is critical, subsequent construction should avoid exceeding this temperature gradient to prevent cracking of large-volume concrete.

[0053] In this embodiment, the thermostat is preferably a thermostat with a measurement accuracy of ±20μW. The software used in the calculation process of this embodiment includes CAD, COMSOL Multiphysics, and Revit. The experimental materials included: P.O42.5 ordinary Portland cement with a standard consistency water requirement of 28.9%, 3-day and 28-day cubic compressive strengths of 28.8 MPa and 53.0 MPa, respectively, and initial and final setting times of 214 mins and 291 mins, respectively; Grade I fly ash with a fineness of 7.9%, loss on ignition of 2.6%, and water requirement of 90%; S95 grade slag powder with 98% activity, a specific surface area of ​​420 m² / kg, and a fluidity ratio of 105%; 5-25mm continuously graded limestone as coarse aggregate with 4% needle-like and flaky content, 1.1% mud content, and a crushing value of 7%; river sand as fine aggregate with a medium sand, fineness modulus of 2.6, and mud content of 1.9%; high-performance polycarboxylate superplasticizer with a solid content of 11%, a water reduction rate of 27%, and a paste fluidity of 248 mm; and C30P8 concrete as used in the experiment, with the following mix design:

[0054] Experimental concrete mix proportions

[0055]

[0056] The experiment was conducted according to the raw material mixing ratio. After weighing the cementitious material, it was stirred with pure water after reverse osmosis. The sample mass was selected as 11.10g, the experimental temperature was 20℃, and the sample was placed in an ampoule for testing. The heat flow during the hydration process of the sample was monitored by a constant temperature measuring instrument TAM AIR.

[0057] The steps involved in calculating the degree of hydration field through coupling with a hydration model are as follows:

[0058] The degree of hydration is used to describe the extent of hydration of cementitious materials. The degree of hydration is:

[0059]

[0060] Where Q(t) is the heat of hydration as a function of time, Qpot is the heat of complete hydration, t represents time, and the hydration rate is calculated using Cervera's Affinity Law model (2), and the hydration rate is:

[0061]

[0062] Where α is the degree of hydration, α max The maximum hydration degree that the material can achieve, where B1 and B2 represent fitting parameters, is calculated using the formula proposed by Shindler and Folliard (3). The maximum hydration degree is:

[0063]

[0064] Wherein SL and FA are the admixture amounts of mineral powder and fly ash, respectively, and Q max ω / c represents the maximum heat release that cement can achieve during hydration, and ω / c represents the maximum degree of hydration. When using P.O42.5 cement, Q max = 330 J / g, considering that the heat release of the mineral admixture is 25% of that of cement, then Q max =255J / g.

[0065] The steps involved in calculating the temperature field through a coupled heat transfer model are as follows:

[0066] Assuming heat transfer in concrete is solid-phase heat transfer, and the internal heat transfer mechanism is solely heat conduction, following Fourier's law, it can be written as:

[0067]

[0068] Where λ is the thermal conductivity of concrete, C p ρ is the specific heat capacity, Q is the heat of hydration, ρ is the density of concrete, ▽ represents the gradient, and T represents the temperature. It represents the derivative of temperature with respect to time, that is, the rate of change of temperature over time;

[0069] The strain decomposition of concrete is as follows:

[0070] ε=ε0+ε bc +ε ds +ε au +ε T (5)

[0071] Where ε0 is the elastic strain, ε ds For the basic creep strain, ε ds For drying (shrinkage) strain, ε au For self-contractile strain, ε T For temperature strain;

[0072] The temperature strain is:

[0073] ε T =α T (TT ref (6)

[0074] Where, α T TT is the coefficient of linear expansion of concrete. ref This represents the temperature change value.

[0075] The strains of drying shrinkage and autogenous shrinkage were calculated using the method in the ZPBazant B4 model, i.e., using formula (6).

[0076] Creep was calculated using De Schutter's generalized Kelvin rheological model, such as... Figure 2 As shown, it is assumed that the elastic modulus E1 and viscosity η1 in the Kelvin element are related to the degree of hydration.

[0077] The calculations using a mechanical model include the following steps:

[0078] The elastic modulus and other properties of concrete, ψ, are calculated using the following formula:

[0079]

[0080] Among them Ψ 28 For its final performance development value, α is the maximum degree of hydration, α0 is the initial value of the degree of hydration, and α max The maximum degree of hydration achievable by the material; the values ​​of Φ for different properties are shown in the table below:

[0081] Mechanical properties with hydration degree development index Φ

[0082] ψ Φ compressive strength 1 elastic modulus 0.67 tensile strength 0.67

[0083] Tetrahedral meshes were used to mesh the computational geometry, with a minimum element size of 100 mm and a maximum element size of 5500 mm. The meshing for the three-stage casting was as follows: Figure 3 As shown:

[0084] In heat transfer calculations, the boundary condition is a heat flux boundary, and the heat flux q passing perpendicular to the boundary direction is... con for:

[0085] q con =H i ·(T ext -T) (8)

[0086] Where H i Here, T represents the equivalent heat transfer coefficient at different environmental heat transfer boundaries, and T represents the ambient temperature.

[0087] Based on the pouring time, the daily average maximum / minimum temperature is set according to the sine function T. ext =27+5sin[2π(x-0.25[d])] changes, such as Figure 4 As shown.

[0088] Statistical table of parameters used in the calculation

[0089]

[0090]

[0091] In the mechanical boundary, the bottom of the soil layer is fixed, there is no horizontal displacement on the sides, and there is no vertical displacement at the bottom support. The remaining boundaries are free boundaries, and the contact boundary between the foundation and concrete is continuous. Figure 5 As shown:

[0092] The initial values ​​(t=0) are: hydration degree = 0.01, and the other variables T and their time partial derivatives. All are 0.

[0093] Preferably, after executing step S2 and before executing step S3, the following steps are performed: simulating the actual concrete pouring process, calculating the degree of hydration field through a hydration model coupling, calculating the temperature field through a heat transfer model coupling, and calculating the evolution of the mechanical properties, shrinkage, and creep of the concrete through the degree of hydration field. The evolution of the mechanical properties, shrinkage, and creep of the concrete, along with the temperature field, are then used to calculate the strain and stress fields through a mechanical model. The risk of concrete cracking is analyzed using the strain and stress fields, and the relationship between the cracking risk and the temperature gradient is analyzed and calculated. It is then determined whether the cracking risk corresponding to the preset temperature gradient value exceeds 0.7. If yes, the process returns to step S2; otherwise, step S3 is executed.

[0094] Preferably, the method for analyzing the risk of concrete cracking through strain and stress field analysis is as follows: using the ratio of the first principal stress to the average tensile strength σ1 / f ctm Analysis revealed that when the first principal stress exceeds the average tensile strength, concrete will crack. A crack risk cloud map was used to illustrate the change in the overall crack risk of large-volume concrete over time. Temperature measurement points were located vertically at the center of the plane based on the relationship between crack risk and temperature gradient.

[0095] In addition to the maximum first principal stress, attention should also be paid to the maximum concrete temperature. If it exceeds 70℃, the delayed ettringite reaction may cause the concrete to crack. The temperature usually reaches its maximum 2-3 days after pouring, at which point the first principal stress inside the cast block will reach its early peak. Therefore, it is crucial to observe the temperature and first principal stress distribution cloud map 3 days after each pour. A digital insertion resistance thermometer (measuring range -30~50℃, error ±0.2℃, display accuracy 0.1℃) should be used to measure the concrete temperature upon entering the pump and upon entering the formwork.

[0096] Within 3 to 28 days after pouring, the surface temperature decreases over time, the temperature gradient drops from 46℃ to 26℃, the core temperature drops from about 68℃ to 55℃, and the temperature difference between the surface and the interior increases from 24℃ to 29℃.

[0097] The temperature gradient at which the cracking risk is 0.7 is used as the temperature gradient control index. The changes in temperature and cracking risk along the vertical direction at the center point of the structure's plane 14 days after pouring are taken as the object of study. Figure 6 As shown:

[0098] After processing, mineral powder and fly ash are naturally cooled and placed in the factory for at least 7 days. They are then transported to the concrete mixing plant in sealed tank trucks and stored in a dry warehouse at a constant temperature, ensuring that the raw materials are always kept below 40°C. Sand and gravel are stored in a closed warehouse, where water spraying is used to lower the temperature of the raw materials, and the air conditioning system is turned on to maintain the indoor temperature below 20°C, so that the raw materials are kept at a low temperature before the concrete is mixed. Ice chips and water are mixed together, and dry ice is used to assist in cooling. The principle of heat absorption by sublimation and melting physical changes is used to lower the temperature of the water, ensuring that the concrete outlet temperature is ≤25°C.

[0099] The concrete transport truck is wrapped with heat-insulating cotton blankets to effectively reduce the transfer of heat from the atmosphere; before the concrete is poured into the truck and the vehicle leaves the station, the tank is sprayed with cold water below 20°C to cool it down again.

[0100] The on-site concrete pouring pump pipe adopts a "one-for-one" method, and the temperature inside the pump pipe is monitored in real time; if the pipe is blocked, the spare pump pipe is replaced in time.

[0101] The two pump pipes used for concrete pouring were wrapped with reflective film on the outside.

[0102] Preferably, when setting measuring points at intervals between the surface and bottom layers, measuring points are set at 600mm intervals on the surface layer and at 800mm intervals on the bottom layer. Specifically, temperature sensors are embedded vertically (height-wise) within the large volume of concrete for temperature monitoring, with sensors 1-4 spaced 800mm apart and sensors 4-8 spaced 600mm apart. Figure 7 As shown, during the pouring of large-volume concrete, ensuring that the cooling rate does not exceed 20K / m effectively prevents concrete cracking.

[0103] This invention utilizes a multi-physics coupling evaluation method to control the temperature gradient of C30 concrete, deriving the relationship between cracking risk and temperature gradient. It also establishes the location of temperature measurement points along the vertical direction at the center of the concrete plane, solving the technical problem in existing technologies where the arrangement and monitoring of temperature measurement points in large-volume concrete cannot meet temperature monitoring requirements. This method controls the temperature upon placement in the formwork through physical methods such as optimizing the cementitious material composition, controlling the temperature of raw materials, cooling during transportation, and wrapping pump pipes with heat-reflective materials at the construction site. Ultimately, it controls the temperature gradient between the surface and the bottom layer below the critical value, achieving the temperature control target to reduce concrete shrinkage, lower the concrete shrinkage rate, prevent cracking in large-volume concrete, and further improve concrete performance.

[0104] All parts not described in this invention are the same as or can be implemented using existing technologies. The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, shall still fall within the scope of the present invention.

Claims

1. A method for controlling the temperature gradient of concrete under multi-physics field coupling evaluation, characterized in that, Includes the following steps: S1. Conduct an adiabatic temperature rise test on the concrete to be poured and obtain the test results, then proceed to step S2. S2. Prepare concrete samples based on a preset temperature gradient value, and conduct a hydration heat test on the concrete samples using the preset temperature gradient value to obtain the hydration heat test results, which include hydration heat and hydration rate. S3. Calculate the degree of hydration based on the results of the heat of hydration test and compare it with the results of the adiabatic temperature rise test: If the degree of hydration and the hydration rate are the same in the two tests, then the preset temperature gradient value is set as the critical value, and then step S4 is executed; If the degree of hydration and hydration rate of the two tests are inconsistent, adjust the preset temperature gradient value and return to step S2; S4. Prepare concrete according to the material composition of the current concrete sample, and control the pouring temperature through physical methods during concrete pouring. Finally, control the temperature gradient between the surface and the bottom layer below the preset temperature gradient value. Set measuring points at intervals between the surface and the bottom layer, and use the temperature difference between the measuring points of the surface and the bottom layer as the temperature gradient monitoring data. After performing step S2 and before performing step S3, the following steps are performed: The actual concrete pouring process is simulated. The hydration degree field is calculated by coupling a hydration model, and the temperature field is calculated by coupling a heat transfer model. The evolution of the mechanical properties, shrinkage, and creep of the concrete is calculated using the hydration degree field. The evolution of the mechanical properties, shrinkage, and creep of the concrete, together with the temperature field, is used to calculate the strain and stress fields through a mechanical model. The risk of concrete cracking is analyzed using the strain and stress fields. The relationship between the cracking risk and the temperature gradient is analyzed and calculated. It is determined whether the cracking risk corresponding to the preset temperature gradient value exceeds 0.

7. If yes, return to step S2; if no, proceed to step S3.

2. The method for controlling the temperature gradient of concrete under multiphysics field coupling evaluation according to claim 1, characterized in that, The steps involved in calculating the degree of hydration field through coupling with a hydration model are as follows: The degree of hydration is used to describe the extent of hydration of cementitious materials. The degree of hydration is: Where Q(t) is the heat of hydration as a function of time, Qpot is the heat of complete hydration, and t represents time; The hydration rate is: Where α is the degree of hydration, α max The maximum degree of hydration that the material can achieve, where B1, B2 and η represent the fitting parameters; The maximum degree of hydration α that the material can achieve max for: Wherein SL and FA are the admixture amounts of mineral powder and fly ash, respectively, and Q max ω / c represents the maximum heat release that cement can achieve during hydration, and ω / c represents the maximum degree of hydration of the concrete sample.

3. The method for controlling the temperature gradient of concrete under multiphysics field coupling evaluation according to claim 1, characterized in that, The calculations using a mechanical model include the following steps: The elastic modulus ψ of concrete is calculated using the following formula: Among them Ψ 28 The final value of its performance development after 28 days, where α is the degree of hydration, α0 is the initial value of the degree of hydration, and α... max The maximum degree of hydration that the material can achieve; In heat transfer calculations, the boundary condition is a heat flux boundary, and the heat flux q passing perpendicular to the boundary direction is... con for: q con =H i ·(T ext -T) Where H i Here, T represents the equivalent heat transfer coefficient at different environmental heat transfer boundaries, and T represents the ambient temperature. Based on the pouring time and the ambient temperature T ext According to the variation of the sine function, the expression is: T ext =27+5sin[2π(x-0.25[d])]。 4. The method for controlling the temperature gradient of concrete under multiphysics field coupling evaluation according to claim 1, characterized in that, The method for analyzing the risk of concrete cracking using strain and stress field analysis is as follows: The ratio σ1 / f of the first principal stress to the average tensile strength ctm Analysis shows that if the first principal stress is greater than the average tensile strength, the concrete will crack. The crack risk cloud map shows how the overall crack risk of the concrete changes over time.

5. The method for controlling the temperature gradient of concrete under multiphysics field coupling evaluation according to claim 1, characterized in that, When setting measuring points at intervals between the surface and the bottom layer, the measuring points should be set at intervals of 600mm on the surface layer and 800mm on the bottom layer.

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