A method for controlling cracking of a gradient mass concrete

Abstract

The present application relates to a kind of gradient mass concrete cracking control method, mass concrete is divided into three layers pouring from bottom to top in medium exothermic zone, high heat zone and fast heat dissipation shrinkage zone, and stepwise material design is carried out to the characteristics of each layer using modified bentonite, basalt low-heat aggregate and retarder, magnesium oxide expansion agent, by constructing temperature deformation, shrinkage deformation, constraint deformation and interlayer coordination formula, the deformation of each layer is accurately quantified and the interlayer deformation difference is controlled, and the gradient cracking control system of partition control-formula quantization-material adaptation is formed.The method of the present application can control the constraint deformation of each layer to be within 0.5mm, and the interlayer deformation difference is ≤0.0015mm / m, which is much lower than the control threshold of 0.15mm / m.The present application eliminates the generation of penetrating cracks, surface cracks and interlayer cracks from the root, and guarantees the integrity and impermeability of mass concrete structure.

Description

Technical Field

[0001] This invention belongs to the field of building construction technology, and specifically relates to a method for controlling cracking in gradient-type large-volume concrete. Background Technology

[0002] Mass concrete is widely used in engineering fields such as high-rise building foundations, large bridge abutments, industrial plant equipment foundations, and water conservancy projects. In actual construction, due to the large volume of concrete and the concentrated amount of cementitious materials used, the cement hydration reaction releases a large amount of heat, resulting in a significant temperature gradient between the interior and surface of the concrete, which in turn causes thermal expansion and contraction deformation. At the same time, the concrete undergoes multiple stages such as plastic shrinkage, drying shrinkage, and creep shrinkage during the hardening process, and volume shrinkage is inevitable, further aggravating the degree of deformation.

[0003] Furthermore, after large-volume concrete is poured, it is subject to various constraints from the foundation soil, adjacent structures, and formwork support. These constraints hinder the free deformation of the concrete, leading to significant tensile stress within it. When this tensile stress exceeds the concrete's tensile strength limit, it easily generates through cracks, surface cracks, or interlayer cracks. These cracks not only compromise the integrity and impermeability of the concrete structure but also accelerate the corrosion of internal steel reinforcement, reduce the structure's load-bearing capacity, and cause safety hazards such as leakage and structural damage. This severely impacts the project's service life, significantly increases subsequent maintenance and reinforcement costs, and may even lead to rework, resulting in substantial economic losses.

[0004] Currently, existing technologies for controlling cracking in large-volume concrete still have many shortcomings. Most methods rely on the overall addition of admixtures, surface insulation curing, single-material modification, or general layered pouring, without fully considering the differences in heat release characteristics, constraint conditions, and deformation requirements of different regions of the large-volume concrete. Existing technologies lack precise gradient design and targeted control for these regional differences, resulting in low precision in deformation control and difficulty in completely eliminating cracking risks. Furthermore, they suffer from problems such as unreasonable material proportions, indiscriminate use of control materials, non-standard construction procedures, high material waste, and low construction efficiency. These technologies cannot meet the high-standard construction quality requirements of various large-scale projects for large-volume concrete, nor can they adapt to the crack control needs of large-volume concrete under different working conditions.

[0005] Therefore, how to provide a method for controlling cracking in gradient-type large-volume concrete is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] To address the shortcomings of existing crack control technologies for large-volume concrete that fail to consider the differences in heat release characteristics and constraint conditions in different regions, resulting in low precision in deformation control and difficulty in completely eliminating cracking risks, this invention provides a gradient-based crack control method for large-volume concrete that can achieve precise zonal control and ensure coordinated interlayer deformation.

[0007] To solve the above technical problems, the present invention includes the following technical solutions:

[0008] A method for controlling cracking in gradient-type mass concrete includes the following steps:

[0009] Step S1, Stepped Layering of Concrete: The large volume of concrete to be poured is divided into three layers from bottom to top along the thickness direction: the bottom layer as the medium heat release zone, the middle layer as the high heat zone, and the top layer as the rapid heat dissipation and shrinkage zone. The bottom layer of concrete can conduct heat through the ground, the middle layer of concrete can only rely on the surrounding area to transfer heat to the outside, and the top layer of concrete is in contact with the air. Part of the heat can be dissipated through the air, and the other part of the concrete surface is exposed to the air, which will also have obvious drying shrinkage behavior.

[0010] Step S2, concrete stepped material design: Based on the heat release characteristics and constraint conditions of each layer, a differentiated mix design is carried out. The bottom layer is mixed with modified bentonite to stabilize the linear expansion coefficient and optimize the adaptability of constraint deformation. The middle layer uses basalt low-heat aggregate and adds retarder to delay the peak of hydration heat release. The top layer is mixed with expansion agent to compensate for shrinkage deformation.

[0011] Step S3, concrete layer deformation control: This includes calculating the temperature deformation, shrinkage deformation, and constraint deformation of each layer separately, and judging whether the standard is met based on the interlayer deformation coordination standard. If the standard is not met, the material or construction parameters are adjusted until the requirements are met.

[0012] Furthermore, in step S2, the bottom layer of concrete is 1m thick. 3 The concrete raw material usage includes the following raw materials: ordinary low-heat cement, fly ash, mineral powder, crushed stone aggregate, medium sand, water, polycarboxylate superplasticizer, modified bentonite, and polypropylene fiber. The unit dosage ratio of each component is specified in kg / m³. 3The following is the mix composition: ordinary low-heat cement 200-240g, fly ash 80-120g, mineral powder 80-100g, crushed stone aggregate 1000-1300g, medium sand 600-700g, water 150-180g, polycarboxylate superplasticizer 3.5-4.5g, modified bentonite 2.0-3.0g, and polypropylene fiber 1.0-2.0g. The modified bentonite is obtained by modifying natural bentonite with the inorganic modifier sodium carbonate. Inorganic modification improves the dispersibility and toughness of bentonite, preventing it from clumping in concrete, and simultaneously enhancing its bonding force with cement and aggregates, thereby better filling concrete pores and stabilizing deformation parameters. The bottom layer concrete is optimized based on the C30 grade concrete mix proportion. The role of modified bentonite in the bottom layer concrete is:

[0013] Firstly, the toughness and deformation adaptability of the bottom layer of concrete can be finely adjusted to avoid the constrained deformation ΔL caused by strong foundation constraints. Y,1 Exceeding the standard.

[0014] Secondly, the coefficient of linear expansion of the bottom layer of concrete should be maintained at α1 = 1.15 × 10⁻⁶. -5 / ℃, reducing localized abnormal temperature deformation caused by material inhomogeneity and ensuring the amount of temperature deformation ΔL T,1 Accurate calculations and compliant control.

[0015] Third, modified bentonite can fill the pores inside concrete, increase the density of the bottom layer of concrete, indirectly reduce the fluctuation of the shrinkage coefficient β1, and reduce microcracks caused by uneven local shrinkage deformation.

[0016] Furthermore, in step S2, the intermediate layer concrete is 1m thick. 3 The concrete raw material usage includes the following raw materials: low-heat slag cement, fly ash, mineral powder, low-heat basalt aggregate, medium sand, water, polycarboxylate superplasticizer, and retarder. The unit dosage ratio of each component is specified in kg / m³. 3 The following are the components: 180-220 parts low-heat slag cement, 100-140 parts fly ash, 80-100 parts mineral powder, 1000-1300 parts low-heat basalt aggregate, 600-700 parts medium sand, 150-180 parts water, 4.0-5.0 parts polycarboxylate superplasticizer, and 0.6-1.0 parts retarder; the retarder is selected from at least one of modified lignin sulfonate, sodium gluconate, or citric acid.

[0017] Furthermore, in step S2, the uppermost layer of concrete is 1m thick. 3 The concrete raw material usage includes the following raw materials: ordinary low-heat cement, fly ash, mineral powder, ceramsite lightweight aggregate, medium sand, water, early-strength high-efficiency water-reducing agent, and expansion agent. The unit dosage ratio of each component is specified in kg / m³. 3The following are the components: ordinary low-heat cement 210~250, fly ash 70~110, mineral powder 80~100, ceramsite lightweight aggregate 1000~1300, medium sand 600~700, water 150~180, early-strength high-efficiency water-reducing agent 3.8~4.8, and expansion agent 16~20; the expansion agent includes magnesium oxide expansion agent, ettringite expansion agent, or calcium oxide-calcium sulfoaluminate composite expansion agent.

[0018] Furthermore, in step S3, the temperature deformation ΔL of the i-th layer of concrete... T,i Calculate using the following formula:

[0019] ,

[0020] In the formula, L0 is the longest side length of the base plate, α i Let T be the coefficient of linear expansion of the concrete in the i-th layer. max,i T represents the highest temperature of the concrete in the i-th layer. env The ambient temperature during construction is considered; and the interlayer temperature deformation difference is controlled to be ≤0.1mm. The difference between the highest concrete temperature and the ambient temperature during construction is T. max,i -T env These factors collectively determine the magnitude of temperature deformation. The core is to quantify the impact of temperature changes on the deformation of each concrete layer, providing a basis for controlling the temperature deformation difference between layers.

[0021] Furthermore, in step S3, the shrinkage deformation amount ΔL between the intermediate layer and the bottom layer... s,i Calculate using the following formula:

[0022] ,

[0023] The shrinkage deformation of the uppermost layer is calculated using the following formula:

[0024] ,

[0025] In the formula, L0 is the longest side length of the base plate, β i Let δ be the shrinkage coefficient of the i-th layer, t be the shrinkage period, and δ be the expansion compensation coefficient of the top layer; the difference in shrinkage deformation between the top layer and other layers should be controlled to be ≤0.05mm. The middle and bottom layers only consider their own shrinkage. The top layer, due to the addition of an expansion agent, needs to have part of its shrinkage compensated by the expansion compensation coefficient δ. The core is to quantify the shrinkage deformation and control it through the expansion agent to avoid excessive shrinkage leading to cracking. Key parameter requirements: β1=0.000012 / d, β2=0.000010 / d, β3=0.000025 / d; t=28d; δ=0.000015-0.000020 / d.

[0026] Further, the constrained deformation of the i-th layer of concrete in step S3 is calculated using the following formula:

[0027] ,

[0028] In the formula, ΔL T,i Let ΔL be the temperature deformation. S,i μ is the amount of shrinkage deformation. i ΔL is the constraint coefficient of the i-th layer under the constraint of the foundation and adjacent layers; and the constraint deformation of each layer is controlled to be ≤0.5mm. Y,i Let be the actual deformation of the i-th layer of concrete during actual construction, constrained by the foundation and the concrete layers above and below. It is the temperature deformation ΔL. T,i With shrinkage deformation ΔL S,i Multiply by the constraint coefficient μ i The sum of these parameters is crucial, with the core objective being to quantify the impact of constraints on the actual deformation of concrete and to define the control thresholds for the actual deformation of each layer. Key parameter requirements: μ1 = 0.8-0.9, μ2 = 0.6-0.7, μ3 = 0.4-0.5.

[0029] Furthermore, the interlayer deformation compatibility criterion mentioned in step S3 is determined by the following formula:

[0030] ,

[0031] In the formula, ΔL Y,i and ΔL Y,j Let L0 be the longest side length of the base slab, representing the different constraint deformation amounts between any two layers. If the above formula is not satisfied, it is considered substandard. The left side of the formula represents the ratio of the constraint deformation difference between any two layers (i≠j) to the side length of the base slab. The core principle is to control the deformation difference between any two layers, ensuring coordinated deformation of the three concrete layers and preventing stress caused by excessive interlayer deformation differences (e.g., exceeding 0.15 mm / m), which can lead to interlayer cracking. This is the core criterion for crack control. Control requirement: Constraint deformation difference between any two layers ≤ 0.15 mm / m; failure to meet this requirement necessitates adjustments to materials or construction parameters.

[0032] Furthermore, in step S1, the thickness of the bottom layer accounts for 33.3% of the total thickness, the thickness of the middle layer accounts for 41.7% of the total thickness, and the thickness of the top layer accounts for 25% of the total thickness.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] (1) The crack control method for gradient-type mass concrete provided by this invention addresses the differences in heat release characteristics and constraint conditions in different regions of mass concrete by employing a gradient material adaptation design. The bottom layer, modified bentonite, stabilizes the coefficient of linear expansion and optimizes the adaptability to constraint deformation. The middle layer uses basalt low-heat aggregate and retarder to delay the peak heat release of hydration. The top layer, magnesium oxide expansive agent, precisely compensates for shrinkage deformation. The three control materials each perform their respective functions and work synergistically, effectively avoiding the problem of insufficient control by a single material and ensuring that the performance of each layer of concrete is precisely matched with the regional characteristics. The materials have strong adaptability and precise control effect.

[0035] (2) The crack control method for gradient-type mass concrete provided by this invention precisely quantifies the temperature deformation, shrinkage deformation, and constraint deformation parameters of each layer through four core deformation coordination formulas, and clarifies the specific dosage of each control material, thus achieving quantifiable and controllable deformation. Example data shows that the method of this invention can control the constraint deformation of each layer within 0.5 mm (the measured maximum value is only 0.335 mm), and the interlayer deformation difference is ≤0.0015 mm / m, far below the control threshold of 0.15 mm / m. In contrast, when traditional monolithic casting is used without gradient material design, under the same base plate size and temperature conditions, simulation calculations show that the maximum constraint deformation can reach 0.72 mm, and the interlayer deformation difference is as high as 0.28 mm / m, far exceeding the coordination standard, which easily leads to through cracks. This invention fundamentally eliminates the generation of through cracks, surface cracks, and interlayer cracks, ensuring the integrity and impermeability of the mass concrete structure. Detailed Implementation

[0036] The following detailed description, in conjunction with specific embodiments, provides a further detailed explanation of the crack control method for gradient-type large-volume concrete provided by the present invention. The advantages and features of the present invention will become clearer from the following description.

[0037] Example 1

[0038] The following describes a method for controlling cracking in gradient-type large-volume concrete provided by the present invention, with reference to specific embodiments.

[0039] The foundation slab of the underground parking garage of a high-rise building is a large-volume concrete project. The slab is 60m long, 40m wide, and 1.2m thick, with a design strength grade of C30. The ambient temperature during construction is T. env At 20℃, the gradient cracking control method of this invention is used for construction, and the specific steps are as follows:

[0040] The first step is to layer the concrete in a stepped manner:

[0041] Based on engineering experience and the estimated temperature deformation formula, the 1.2m thick base plate is divided into three layers: the bottom layer is 0.4m thick, accounting for 33.3%; the middle layer is 0.5m thick, accounting for 41.7%; and the top layer is 0.3m thick, accounting for 25%. This layering ratio ensures that the temperature deformation difference between each layer has an adjustable range that meets the coordination requirements.

[0042] The second step is the design of a stepped concrete material system.

[0043] The bottom layer (medium-heated zone) of concrete is prepared according to the following unit mix ratio: 220kg of ordinary low-heat cement, 100kg of fly ash, 90kg of mineral powder, 1160kg of ordinary crushed stone aggregate, 660kg of medium sand, 164kg of water, 4.1kg of polycarboxylate superplasticizer, 2.46kg of modified bentonite, and 1.64kg of polypropylene fiber.

[0044] The intermediate layer (high-heat zone) concrete is prepared according to the following single-component mix proportions: 200kg low-heat slag cement, 120kg fly ash, 90kg mineral powder, 1150kg low-heat basalt aggregate, 650kg medium sand, 164kg water, 4.5kg polycarboxylate superplasticizer, and 0.8kg modified lignin sulfonate retarder.

[0045] The top layer (rapid heat dissipation and shrinkage zone) is prepared with the following single-component concrete mix proportions: 230 kg of ordinary low-heat cement, 90 kg of fly ash, 90 kg of mineral powder, 1120 kg of ceramsite lightweight aggregate, 670 kg of medium sand, 164 kg of water, 4.3 kg of early-strength high-efficiency water-reducing agent, and 18 kg of magnesium oxide expansion agent.

[0046] Step 3: Controlling concrete layer deformation:

[0047] (1) Layer thickness: Total thickness 1.2m, combined with the formula for temperature deformation:

[0048] ,

[0049] Temperature parameters were determined based on the characteristics of the engineering area: the thickness of the bottom layer was 0.4m (accounting for 33.3%), the thickness of the middle layer was 0.5m (accounting for 41.7%), and the thickness of the top layer was 0.3m (accounting for 25%), to ensure that the temperature deformation difference between each layer met the coordination requirements.

[0050] (2) Temperature parameters: Based on engineering experience and formula estimation, the temperature of the lowest layer is determined. max,1 =50℃, intermediate layer T max,2 =65℃, top layer T max,3 =55℃, ambient temperature T env =20℃, providing a basis for subsequent deformation calculations.

[0051] (3) Deformation calculation (calculated length of base plate L0 = 60m):

[0052] Temperature deformation: Substitute into the formula:

[0053]

[0054] The bottom layer ΔLT, 1 = 60 × 1.15 × 10 -5 ×(50-20)=0.207mm; Intermediate layer ΔL T,2 =60×1.2×10 -5 ×(65-20)=0.324mm; Top layer ΔL T,3 =60×1.25×10 -5 ×(55-20)=0.2625mm.

[0055] Shrinkage deformation: Substitute into the formula, middle layer, bottom layer:

[0056]

[0057] Top layer:

[0058]

[0059] The bottom layer ΔL S,1 =60×0.000012×28=0.02016mm; Intermediate layer ΔL S,2 =60×0.000010×28=0.0168mm; Top layer ΔL S,3 =60×(0.000025×28-0.000018)=0.0132mm (δ=0.000018 / d, calculated based on the amount of expanding agent).

[0060] Constraint deformation amount: Substitute into the formula

[0061]

[0062] The bottom layer ΔL Y,1 =0.207 + 0.02016 × 0.85 = 0.224 mm; Intermediate layer ΔL Y,2 =0.324 + 0.0168 × 0.65 = 0.335 mm; Top layer ΔL Y,3 =0.2625+0.0132×0.45=0.268mm.

[0063] Deformation compatibility verification: Substituting into the formula

[0064]

[0065] The deformation difference between any two layers is ≤0.15mm / m (e.g., the deformation difference between the middle layer and the top layer = |0.335-0.268| / 60≈0.0011mm / m, which meets the requirements), verifying the reasonableness of the parameters. The calculation results of the key deformation parameters are shown in Table 1.

[0066] Table 1 Summary of Calculation Results of Key Deformation Parameters in Example 1

[0067] bottom layer 0.207 0.02016 0.224 Intermediate layer 0.324 0.0168 0.335 Top layer 0.2625 0.0132 0.268

[0068] Construction was carried out according to these parameters. Testing was conducted 28 days after construction. The base slab surface was smooth, with no through cracks, surface cracks, or interlayer cracking found. The overall structural integrity and impermeability were excellent. This example demonstrates that the method of the present invention can accurately quantify and coordinate the deformation of each layer, effectively eliminating the risk of cracking in large-volume concrete.

[0069] Comparative Example 1

[0070] Using a similar foundation slab project (total length 60m, total thickness 1.2m) as the model, a simulation calculation was performed using the traditional monolithic casting method without gradient material design. The traditional method employed a single C30 mix proportion: 230kg ordinary low-heat cement, 90kg fly ash, 90kg mineral powder, 1160kg ordinary crushed stone aggregate, 660kg medium sand, 164kg water, and 4.3kg polycarboxylate superplasticizer. No modified bentonite, no basalt aggregate, and no expansive agent were used. The constraint coefficients were set at 0.9 for the bottom, 0.7 for the middle, and 0.5 for the top. The results, calculated using the same formula, are shown in Table 2.

[0071] Table 2 Summary of Calculation Results of Deformation Parameters for Traditional Integral Casting in Comparative Example 1

[0072] bottom 0.230 0.0336 0.260 Central 0.346 0.0336 0.369 upper part 0.274 0.0336 0.291

[0073] Calculating the interlayer deformation difference: The deformation difference between the middle and bottom is #imgpt21# mm / m, and the deformation difference between the middle and the top is #imgpt22# mm / m. It seems to meet the requirements, but at this time, the shrinkage compensation and constraint optimization caused by the gradient material are not considered. The shrinkage deformation of the top layer is not compensated at all. In reality, due to the increased shrinkage due to drying, if the shrinkage coefficient of the top layer is increased to #imgpt23# mm according to the actual exposure conditions, the shrinkage deformation of the top layer will reach #imgpt24# mm, the constraint deformation will reach #imgpt25# mm, and the deformation difference between the middle and the top layer will rise to #imgpt26#.

[0074] The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. The above embodiments only illustrate several implementations of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for controlling cracking in gradient-type large-volume concrete, characterized in that, Includes the following steps: Step S1, concrete stepped layering: Divide the large volume of concrete to be poured into three layers from bottom to top along the thickness direction: the bottom layer as the medium heat release zone, the middle layer as the high heat zone, and the top layer as the rapid heat dissipation and shrinkage zone. Step S2, concrete stepped material design: Based on the heat release characteristics and constraint conditions of each layer, a differentiated mix design is carried out. The bottom layer is mixed with modified bentonite to stabilize the linear expansion coefficient and optimize the adaptability of constraint deformation. The middle layer uses basalt low-heat aggregate and adds retarder to delay the peak of hydration heat release. The top layer is mixed with expansion agent to compensate for shrinkage deformation. Step S3, concrete layer deformation control: This includes calculating the temperature deformation, shrinkage deformation, and constraint deformation of each layer separately, and judging whether the standard is met based on the interlayer deformation coordination standard. If the standard is not met, the material or construction parameters are adjusted until the requirements are met.

2. The method according to claim 1, characterized in that, The bottom layer of concrete in step S2 is 1m thick. 3 The concrete raw material usage includes the following raw materials: ordinary low-heat cement, fly ash, mineral powder, crushed stone aggregate, medium sand, water, polycarboxylate superplasticizer, modified bentonite, and polypropylene fiber. The unit dosage ratio of each component is specified in kg / m³. 3 The following are the components: ordinary low-heat cement 200~240, fly ash 80~120, mineral powder 80~100, crushed stone aggregate 1000~1300, medium sand 600~700, water 150~180, polycarboxylate superplasticizer 3.5~4.5, modified bentonite 2.0~3.0, and polypropylene fiber 1.0~2.0; the modified bentonite is obtained by modifying natural bentonite with the inorganic modifier sodium carbonate.

3. The method according to claim 1, characterized in that, In step S2, the intermediate layer of concrete is 1m thick. 3 The concrete raw material usage includes the following raw materials: low-heat slag cement, fly ash, mineral powder, low-heat basalt aggregate, medium sand, water, polycarboxylate superplasticizer, and retarder. The unit dosage ratio of each component is specified in kg / m³. 3 The following are the components: 180-220 parts low-heat slag cement, 100-140 parts fly ash, 80-100 parts mineral powder, 1000-1300 parts low-heat basalt aggregate, 600-700 parts medium sand, 150-180 parts water, 4.0-5.0 parts polycarboxylate superplasticizer, and 0.6-1.0 parts retarder; the retarder is selected from at least one of modified lignin sulfonate, sodium gluconate, or citric acid.

4. The method according to claim 1, characterized in that, The top layer of concrete in step S2 is 1m high. 3 The concrete raw material usage includes the following raw materials: ordinary low-heat cement, fly ash, mineral powder, ceramsite lightweight aggregate, medium sand, water, early-strength high-efficiency water-reducing agent, and expansion agent. The unit dosage ratio of each component is specified in kg / m³. 3 The following are the components: ordinary low-heat cement 210~250, fly ash 70~110, mineral powder 80~100, ceramsite lightweight aggregate 1000~1300, medium sand 600~700, water 150~180, early-strength high-efficiency water-reducing agent 3.8~4.8, and expansion agent 16~20; the expansion agent includes magnesium oxide expansion agent, ettringite expansion agent, or calcium oxide-calcium sulfoaluminate composite expansion agent.

5. The method according to claim 1, characterized in that, The temperature deformation ΔL of the i-th layer of concrete in step S3 T,i Calculate using the following formula: ， In the formula, L0 is the longest side length of the base plate, α i Let T be the coefficient of linear expansion of the concrete in the i-th layer. max,i T represents the highest temperature of the concrete in the i-th layer. env The ambient temperature during construction; and the temperature deformation difference between layers is controlled to be ≤0.1mm.

6. The method according to claim 5, characterized in that, In step S3, the shrinkage deformation of the middle layer and the bottom layer is calculated using the following formula: ， The shrinkage deformation of the uppermost layer is calculated using the following formula: ， In the formula, L0 is the longest side length of the base plate, β i δ is the shrinkage coefficient of the i-th layer, t is the shrinkage period, and δ is the expansion compensation coefficient of the uppermost layer; and the difference in shrinkage deformation between the uppermost layer and other layers is controlled to be ≤0.05mm.

7. The method according to claim 1, characterized in that, The constrained deformation of the i-th layer of concrete in step S3 is calculated using the following formula: ， In the formula, ΔL T,i Let ΔL be the temperature deformation. S,i μ is the amount of shrinkage deformation. i is the constraint coefficient of the i-th layer under the constraint of the foundation and adjacent layers; and the constraint deformation of each layer is controlled to be ≤0.5mm.

8. The method according to claim 1, characterized in that, The interlayer deformation compatibility criterion mentioned in step S3 is determined by the following formula: ， In the formula, ΔL Y,i and ΔL Y,j Let L0 be the longest side length of the base plate, and let L0 be the different constraint deformation amounts of any two layers. If the above formula is not satisfied, it is judged as not meeting the standard.

9. The method according to claim 1, characterized in that, In step S1, the thickness of the bottom layer accounts for 33.3% of the total thickness, the thickness of the middle layer accounts for 41.7% of the total thickness, and the thickness of the top layer accounts for 25% of the total thickness.

Images