Concrete mix proportion design method for plateau large-temperature-difference bridge pier body

Abstract

The invention relates to the technical field of building materials, and discloses a plateau large-temperature-difference bridge pier body concrete mix proportion design method which comprises the following steps: taking different lithologic materials as part of raw materials of pier body concrete; the lithologic materials comprise gneiss, dolomite, slate, granite, limestone, limestone modified stone powder + granite and granite modified stone powder + limestone, the doping amount of the modified stone powder in the gneiss, dolomite and slate concrete is 30% of the total mass of the cementing material, and the doping amount of the modified stone powder in the granite and limestone concrete is 30% of the total mass of the cementing material; the components in the pier body concrete are uniformly stirred and mixed according to the dosage to obtain a mixture, and the mixture is verified to meet the design requirement. Through the design proportion of the concrete, the bridge pier body concrete has good anti-cracking performance, durability and mechanical performance in the plateau large-temperature-difference environment.

Description

Technical Field

[0001] The present application relates to the technical field of building materials, and in particular to a concrete mix design method for bridge piers with large temperature differences on plateaus. Background Art

[0002] The construction of bridge piers in high altitude areas usually creates a problem. The atmosphere in high altitude areas is thinner, the air density is low, and it usually has unique climatic characteristics, among which the large temperature difference between day and night is a significant phenomenon, which poses a challenge to the construction and long-term performance of bridge pier concrete.

[0003] During the pouring and construction of the bridge pier, the concrete will generate hydration heat during the solidification and hardening process. If this heat cannot be dissipated in time, it will accumulate inside to form a temperature gradient, resulting in a temperature difference between the inside and outside of the concrete. Under the influence of the large temperature difference on the plateau, this temperature difference will be more significant, aggravating the uneven shrinkage inside the concrete, and then generating tensile stress. If these stresses exceed the tensile strength of the concrete, they will cause cracks. In addition, the low oxygen environment and strong wind conditions in the plateau will also affect the curing and strength development of the concrete. As for the long-term performance of concrete for bridges in plateau areas, if the concrete is affected by large temperature differences for a long time, its microstructure may be damaged, resulting in reduced durability of the material and easy cracks on the surface. The generation of cracks not only affects the appearance of the bridge, but may also become a channel for water penetration, freeze-thaw cycles and chemical erosion, all of which will accelerate the deterioration process of the concrete and reduce the service life of the bridge. Summary of the invention

[0004] The present application provides a method for designing concrete mix proportions for bridge piers in plateaus with large temperature differences, thereby solving the technical problem in the prior art that the construction and long-term performance of bridge pier concrete under large temperature differences in plateaus are seriously challenged. The application realizes that through the design mix proportions of concrete, the bridge pier concrete has good crack resistance, durability and mechanical properties under the large temperature difference environment in the plateau.

[0005] The present application provides a method for designing a concrete mix ratio for a bridge pier with a large temperature difference on a plateau, comprising the following steps: using different rock materials as part of the raw materials for the pier concrete, the rock materials including gneiss, dolomite, slate, granite, limestone, limestone modified stone powder + granite, and granite modified stone powder + limestone, wherein the amount of modified stone powder in gneiss, dolomite and slate concrete is 30% of the total mass of the cementitious material, and the amount of modified stone powder in granite and limestone concrete is 30% of the total mass of the cementitious material; stirring and mixing each component in the pier concrete evenly according to the amount to obtain a mixture; testing the working performance of the mixture, and verifying that the mixture meets the design requirements.

[0006] Furthermore, the concrete mix proportions of different rock materials as raw materials include: benchmark group: cement is 314kg / m³, fly ash is 135kg / m³, modified stone powder is 0kg / m³, machine-made sand is 784kg / m³, coarse aggregate is 1039kg / m³, water reducer is 4.49kg / m³, air entraining agent is 0kg / m³, and water is 157kg / m³; gneiss group: cement is 301kg / m³, fly ash is 0kg / m³, modified stone powder is 129kg / m³, machine-made sand is 784kg / m³, coarse aggregate is 1039kg / m³, water reducer is 4.49kg / m³, air entraining agent is 0kg / m³, and water is 157kg / m³. g / m³, water is 151kg / m³; dolomite group: cement is 301kg / m³, fly ash is 0kg / m³, modified stone powder is 129kg / m³, machine-made sand is 784kg / m³, coarse aggregate is 1039kg / m³, water reducer is 4.3kg / m³, air entraining agent is 0kg / m³, water is 151kg / m³; slate group: cement is 301kg / m³, fly ash is 0kg / m³, modified stone powder is 129kg / m³, machine-made sand is 784kg / m³, coarse aggregate is 1039kg / m³, water reducer is 4.3kg / m³, air entraining agent is 0kg / m³, water is 151kg / m³; granite group: cement is 347kg / m³, fly ash is 0kg / m³, modified stone powder is 87kg / m³, machine-made sand is 738kg / m³, coarse aggregate is 1061kg / m³, water reducer is 5.09kg / m³, air entraining agent is 0.5kg / m³, water is 160kg / m³; limestone group: cement is 347kg / m³, fly ash is 0kg / m³, modified stone powder is 87kg / m³, machine-made sand is 738kg / m³, coarse aggregate is 1061kg / m³, water reducer is 3.72kg / m³, air entraining agent is 0.5kg / m³, water is 160kg / m³; lime Rock modified stone powder + granite group: cement is 347kg / m³, fly ash is 0kg / m³, modified stone powder is 87kg / m³, machine-made sand is 738kg / m³, coarse aggregate is 1061kg / m³, water reducer is 5kg / m³, air entraining agent is 0kg / m³, and water is 160kg / m³; granite modified stone powder + limestone group: cement is 347kg / m³, fly ash is 0kg / m³, modified stone powder is 87kg / m³, machine-made sand is 738kg / m³, coarse aggregate is 1061kg / m³, water reducer is 4.75kg / m³, air entraining agent is 0kg / m³, and water is 160kg / m³.

[0007] Furthermore, when the content of modified stone powder of different rock types is 20%-30%, the compressive strength of concrete of the baseline group, gneiss group, dolomite group, slate group, granite group, limestone group, limestone modified stone powder + granite group, and granite modified stone powder + limestone group are 49.1MPa, 48.1MPa, 52.2MPa, 51.2MPa, 50.2MPa, 53.8MPa, 52.0MPa, and 50.3MPa, respectively.

[0008] Furthermore, when the age of concrete reaches 28 days, the flexural strength of concrete of the benchmark group, gneiss group, dolomite group, slate group, granite group, limestone group, limestone modified stone powder + granite group, and granite modified stone powder + limestone group are 5.9 MPa, 5.8 MPa, 6.1 MPa, 6.3 MPa, 6.6 MPa, 6.8 MPa, 6.2 MPa, and 6.3 MPa, respectively.

[0009] Furthermore, when the age of concrete reaches 28 days, the elastic modulus of concrete of the baseline group, gneiss group, dolomite group, slate group, granite group, limestone group, limestone modified stone powder + granite group, and granite modified stone powder + limestone group are 36.5 GPa, 36.7 GPa, 39.5 GPa, 40.3 GPa, 36.9 GPa, 37.2 GPa, 36.8 GPa, and 36.8 GPa, respectively.

[0010] Furthermore, the permeability grades of the benchmark group, gneiss group, dolomite group, slate group, granite group, limestone group, limestone modified stone powder + granite group, and granite modified stone powder + limestone group are all ≥P20, and the frost resistance performance is all ≥F400.

[0011] Furthermore, the slump of the concrete is within 160-200 mm and the air content is within ≥4.0%.

[0012] One or more technical solutions provided in this application have at least the following technical effects or advantages:

[0013] By adopting the concrete mix ratio designed in this application and using different rock materials as part of the concrete raw materials, the technical problem in the prior art that serious challenges to the construction and long-term performance of bridge pier concrete under large temperature differences on the plateau is solved, and the bridge pier concrete has good crack resistance, durability and mechanical properties under large temperature differences on the plateau through the designed concrete mix ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a flow chart of a concrete mix design method for a bridge pier with a large temperature difference on a plateau in an embodiment of the present application;

[0015] Figure 2 A bar graph showing the compressive strength of different lithologies in the embodiments of the present application;

[0016] Figure 3 A bar graph showing the flexural strength of different lithologies in the embodiments of the present application;

[0017] Figure 4 It is a bar graph of the elastic modulus of different lithologies in the examples of this application. DETAILED DESCRIPTION

[0018] In order to better understand the technical solution of the present application, the technical solution of the present application will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0019] Reference Figure 1 , a concrete mix design method for bridge piers with large temperature differences on plateaus, comprising the following steps:

[0020] S1, select concrete raw materials.

[0021] In the specific implementation, the raw materials of concrete include cement, stone powder, coarse and fine aggregates, admixtures, etc., among which different rock materials are used as coarse and fine aggregates of pier body concrete, and the rock materials include gneiss, dolomite, slate, granite, limestone, limestone modified stone powder + granite, and granite modified stone powder + limestone.

[0022] In specific implementation, the concrete mix ratio (unit: kg / m³) of different rock materials as raw materials is shown in the following table.

[0023] Serial number Lithology cement Fly ash Modified stone powder Machine-made sand coarse aggregate Water reducing agent Water diversion agent water 1 Benchmark Group 314 135 / 784 1039 4.49 / 157 2 Gneiss 301 / 129 784 1039 4.3 / 151 3 Dolomites 301 / 129 784 1039 4.3 / 151 4 Slate 301 / 129 784 1039 4.3 / 151 5 granite 347 / 87 738 1061 5.09 0.5 160 6 Limestone 347 / 87 738 1061 3.72 0.5 160 7 Limestone modified stone powder + granite aggregate 347 / 87 738 1061 5 0.5 160 8 Modified granite powder + limestone aggregate 347 / 87 738 1061 4.75 / 160

[0024] Under the above ratio, the modified stone powder content in gneiss, dolomite and slate concrete is 30% of the total mass of cementitious materials, and the modified stone powder content in granite and limestone concrete is 30% of the total mass of cementitious materials. The slump of concrete is within 160-200mm and the air content is ≥4.0%. Among them, water reducers can reduce the amount of water in concrete, help improve the early and late strength of concrete, and allow the amount of cement to be reduced while maintaining the strength unchanged, thereby saving costs. Water reducers can also improve the fluidity and slump of concrete, making concrete easier to construct and form, especially in situations where self-flow or pumping is required. In addition, water reducers can extend the service life of concrete structures by reducing the porosity in concrete, improving the concrete's impermeability, freeze-thaw resistance and chemical corrosion resistance.

[0025] S2, mixing and stirring the components according to the amounts to obtain a mixture.

[0026] In a specific implementation, the above concrete mix is ​​put into a concrete mixer and mixed thoroughly to obtain a mixture.

[0027] S3, verify the mixture.

[0028] In practice, the mix is ​​tested for workability, during which all test data and observations are recorded, the data are analyzed to determine if the concrete meets the design specifications and performance requirements, and if necessary, further adjustments are made to the concrete components based on the analysis results.

[0029] In the specific implementation, the electrical flux of concrete of the benchmark group, gneiss group, dolomite group, slate group, granite group, limestone group, limestone modified stone powder + granite group, and granite modified stone powder + limestone group is less than 1000C. Therefore, the electrical flux of the full-hole slag concrete of the above different rock types is less than 2000C, which meets the technical requirements for low permeability concrete in the ASTMC1202 standard.

[0030] In specific implementation, higher compressive strength means that concrete has better durability and can withstand long-term loads and environmental factors. Compressive strength is an important indicator for evaluating concrete quality. It determines the bearing capacity and stability of concrete structures and is an important parameter for structural design. In addition, appropriate compressive strength can reduce the amount of concrete used, save costs, and also help reduce resource consumption and the environment. The dosage of modified stone powder of different lithologies is 20%-30%. The compressive strengths of concrete of the benchmark group, gneiss group, dolomite group, slate group, granite group, limestone group, limestone modified stone powder + granite group, and granite modified stone powder + limestone group are 49.1MPa, 48.1MPa, 52.2MPa, 51.2MPa, 50.2MPa, 53.8MPa, 52.0MPa, and 50.3MPa, respectively. Please refer to the attached manual for details. Figure 2 Bar graph of medium compressive strength.

[0031] In the specific implementation, in the design of concrete, the flexural strength is crucial to ensure the safety and reliability of the structure. The level of flexural strength is directly related to the performance of concrete in actual engineering applications. When the concrete age reaches 28 days, the flexural strength of the concrete of the benchmark group, gneiss group, dolomite group, slate group, granite group, limestone group, limestone modified stone powder + granite group, and granite modified stone powder + limestone group are 5.9MPa, 5.8MPa, 6.1MPa, 6.3MPa, 6.6MPa, 6.8MPa, 6.2MPa, and 6.3MPa, respectively. Figure 3 Bar graph of medium flexural strength.

[0032] In concrete implementation, the elastic modulus reflects the degree to which concrete can recover to its original state after being subjected to stress. It is a physical property that measures the stiffness and deformation capacity of concrete materials in the elastic stage. When the concrete age reaches 28 days, the elastic modulus of concrete of the benchmark group, gneiss group, dolomite group, slate group, granite group, limestone group, limestone modified stone powder + granite group, and granite modified stone powder + limestone group are 36.5 GPa, 36.7 GPa, 39.5 GPa, 40.3 GPa, 36.9 GPa, 37.2 GPa, 36.8 GPa, and 36.8 GPa, respectively. Figure 3 Histogram of elastic modulus.

[0033] In addition, the impermeability and frost resistance grades of different rock materials as concrete raw materials are shown in the following table.

[0034] Serial number Lithology Impermeability grade Frost resistance level 1 Benchmark Group ≥P20 ≥F400 2 Gneiss ≥P20 ≥F400 3 Dolomites ≥P20 ≥F400 4 Slate ≥P20 ≥F400 5 granite ≥P20 ≥F400 6 Limestone ≥P20 ≥F400 7 Limestone modified stone powder + granite aggregate ≥P20 ≥F400 8 Modified granite powder + limestone aggregate ≥P20 ≥F400

[0035] In the construction process of the bridge pier with large temperature difference on the plateau, measures such as layered pouring, thermal insulation and moisture maintenance, and control of concrete temperature are adopted to construct the bridge pier; the slump of concrete is reduced, and the pouring method is adjusted to hopper delivery; the core idea of ​​layered pouring is to divide the concrete into several layers for construction. This method can effectively avoid the temperature and shrinkage differences of concrete and reduce the risk of concrete cracking; optimize the vibration sequence, "arc first, then straight plate, outside first, then inside"; strictly control the layer thickness, and the single-layer pouring thickness is ≤40cm; enhance the configuration of vibration tools, and use medium 70mm low frequency + ф50mm high frequency inserted vibrating rods to improve the quality of concrete vibration, and the pier body concrete with formwork curing time is further extended to ≥4d; immediately after demolding, use water-saving moisture-retaining film + geotextile + warm water drip irrigation for zero-interval curing, the curing time is greater than 14d, and the long-term wrapping time is maintained for greater than 6 months. During the construction process, the concrete temperature and cracks are monitored in real time, and the construction plan and mix ratio are adjusted according to the actual situation; the core and surface temperature monitoring and data collection frequency of the pier body concrete are increased to guide the timing of on-site formwork removal and curing water temperature control, ensuring that the formwork is not removed before the concrete core temperature begins to cool down, and is not removed when there is strong wind or a sharp change in temperature. The appearance quality of the pier body constructed using this method is significantly improved, and the color difference and cracks of the pier body concrete are effectively reduced.

[0036] To sum up: according to the characteristics of the large temperature difference environment on the plateau, by using different rock materials in high-quality slag as aggregates and then through the concrete mix ratio designed in this application, the technical problems in the prior art that pose serious challenges to the construction and long-term performance of bridge pier concrete under the large temperature difference on the plateau are solved, and the designed mix ratio of concrete is achieved. Under the large temperature difference environment on the plateau, the bridge pier concrete has good crack resistance, durability and mechanical properties, which improves the service life and safety of the bridge pier in the large temperature difference environment on the plateau.

[0037] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

[0038] What has been described above is only a preferred specific implementation manner of the embodiments of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can make equivalent substitutions or changes according to the technical scheme and concept of the present application within the technical scope disclosed in the present application, which should be covered by the protection scope of the present application.

Claims

1. A concrete mix design method for bridge piers with large temperature differences on plateaus, characterized in that: The following steps are involved: Different rock materials are used as part of the raw materials for the pier body concrete, including gneiss, dolomite, slate, granite, limestone, limestone modified stone powder + granite, granite modified stone powder + limestone. The modified stone powder content in gneiss, dolomite and slate concrete is 30% of the total mass of cementitious materials, and the modified stone powder content in granite and limestone concrete is 30% of the total mass of cementitious materials. Stirring and mixing each component in the pier body concrete evenly according to the amount used to obtain a mixture; Conduct working performance tests on the mixture and verify that the mixture meets the design requirements.

2. A concrete mix design method for bridge piers with large temperature differences in plateaus as claimed in claim 1, characterized in that: The concrete mix proportions with different rock materials as raw materials include: Benchmark group: cement is 314kg / m³, fly ash is 135kg / m³, modified stone powder is 0kg / m³, machine-made sand is 784kg / m³, coarse aggregate is 1039kg / m³, water reducer is 4.49kg / m³, air entraining agent is 0kg / m³, water is 157kg / m³; Gneiss group: cement is 301kg / m³, fly ash is 0kg / m³, modified stone powder is 129kg / m³, machine-made sand is 784kg / m³, coarse aggregate is 1039kg / m³, water reducer is 4.3kg / m³, air entraining agent is 0kg / m³, and water is 151kg / m³; Dolomite group: cement is 301kg / m³, fly ash is 0kg / m³, modified stone powder is 129kg / m³, machine-made sand is 784kg / m³, coarse aggregate is 1039kg / m³, water reducer is 4.3kg / m³, air entraining agent is 0kg / m³, and water is 151kg / m³; Slate group: cement is 301kg / m³, fly ash is 0kg / m³, modified stone powder is 129kg / m³, machine-made sand is 784kg / m³, coarse aggregate is 1039kg / m³, water reducer is 4.3kg / m³, air entraining agent is 0kg / m³, water is 151kg / m³; Granite group: cement is 347kg / m³, fly ash is 0kg / m³, modified stone powder is 87kg / m³, machine-made sand is 738kg / m³, coarse aggregate is 1061kg / m³, water reducer is 5.09kg / m³, air entraining agent is 0.5kg / m³, water is 160kg / m³; Limestone group: cement is 347kg / m³, fly ash is 0kg / m³, modified stone powder is 87kg / m³, machine-made sand is 738kg / m³, coarse aggregate is 1061kg / m³, water reducer is 3.72kg / m³, air entraining agent is 0.5kg / m³, water is 160kg / m³; Limestone modified stone powder + granite group: cement is 347kg / m³, fly ash is 0kg / m³, modified stone powder is 87kg / m³, machine-made sand is 738kg / m³, coarse aggregate is 1061kg / m³, water reducer is 5kg / m³, air entraining agent is 0kg / m³, water is 160kg / m³; Granite modified stone powder + limestone group: cement is 347kg / m³, fly ash is 0kg / m³, modified stone powder is 87kg / m³, machine-made sand is 738kg / m³, coarse aggregate is 1061kg / m³, water reducer is 4.75kg / m³, air entraining agent is 0kg / m³, and water is 160kg / m³.

3. A concrete mix design method for bridge piers with large temperature differences in plateaus as claimed in claim 2, characterized in that: The dosage of modified stone powder of different rock types is 20%-30%. The compressive strength of concrete of the benchmark group, gneiss group, dolomite group, slate group, granite group, limestone group, limestone modified stone powder + granite group, and granite modified stone powder + limestone group are 49.1MPa, 48.1MPa, 52.2MPa, 51.2MPa, 50.2MPa, 53.8MPa, 52.0MPa, and 50.3MPa, respectively.

4. A concrete mix design method for bridge piers with large temperature differences in plateaus as claimed in claim 2, characterized in that: When the age of concrete reaches 28 days, the flexural strength of concrete of the benchmark group, gneiss group, dolomite group, slate group, granite group, limestone group, limestone modified stone powder + granite group, and granite modified stone powder + limestone group are 5.9MPa, 5.8MPa, 6.1MPa, 6.3MPa, 6.6MPa, 6.8MPa, 6.2MPa, and 6.3MPa, respectively.

5. A concrete mix design method for bridge piers with large temperature differences in plateaus as claimed in claim 2, characterized in that: When the age of concrete reaches 28 days, the elastic modulus of concrete of the benchmark group, gneiss group, dolomite group, slate group, granite group, limestone group, limestone modified stone powder + granite group, and granite modified stone powder + limestone group are 36.5 GPa, 36.7 GPa, 39.5 GPa, 40.3 GPa, 36.9 GPa, 37.2 GPa, 36.8 GPa, and 36.8 GPa, respectively.

6. A concrete mix design method for bridge piers with large temperature differences in plateaus as claimed in claim 2, characterized in that: The permeability grades of the benchmark group, gneiss group, dolomite group, slate group, granite group, limestone group, limestone modified stone powder + granite group, and granite modified stone powder + limestone group are all ≥P20, and their anti-freeze performance is all ≥F400.

7. A concrete mix design method for bridge piers with large temperature differences in plateaus as claimed in claim 2, characterized in that: The slump of concrete is within 160-200mm and the air content is ≥4.0%.

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