High-performance concrete and reinforcement intensive concrete prestressed ring beam construction method

Abstract

The invention relates to a high-performance concrete and reinforcement intensive concrete prestressed ring beam construction method. The high-performance concrete and reinforcement intensive concrete prestressed ring beam comprises the following components by weight: 280kg of cement, 80kg of fly ash, 48kg of mineral powder, 38kg of an anti-cracking agent, 24kg of a viscosity reducer, 710kg of natural sand, 1065kg of gravel, 7.99 kg of a water reducing agent, 150kg of water and 0.235 kg of cellulose ether. The problem that when the distance between the steel bars is too dense, it can be guaranteed that the difference between the internal temperature and the surface temperature is not large without additionally arranging cooling water pipes, and therefore it is guaranteed that cracking of concrete is effectively controlled is solved.

Description

Technical Field

[0001] The invention relates to the field of construction engineering, in particular to a method for constructing a high-performance concrete and steel-intensive concrete prestressed ring beam. Background Art

[0002] In a certain earth-covered building, there is a large ring beam, which plays a key load-bearing role of "connecting the upper and lower parts". Its profile is as follows: the cross-section is a parallelogram with dimensions of 6.3m (b) × 4.3m (h), the inner side is a hyperbolic ring with an inner diameter circumference of 369m and an outer diameter circumference of 432m; the concrete grade is C60, and the molding effect requirement is fair-faced concrete.

[0003] The main problems in the construction of the above reinforced concrete ring beam are: 1. Due to the large volume of large-volume concrete, the cement hydration process will release a large amount of heat, resulting in a large temperature difference between the internal and surface concrete, thus causing concrete cracking.

[0004] 2. The traditional solution to the problem of large temperature difference between the inner and outer surfaces of large-volume concrete is to adopt cooling measures, such as inserting cooling water pipes inside the structure. However, when the steel bars are too dense, the gaps between the steel bars are very small, making it difficult to insert the cooling water pipes. Summary of the invention

[0005] The present invention aims to overcome the defects of the prior art and provide a method for constructing a high-performance concrete and steel-dense concrete prestressed ring beam, so as to solve the problems of difficulty in vibrating and implementing cooling measures during the pouring process of concrete ring beams with huge cross-sections and dense steel bars, and the problems of cracking and difficulty in controlling heating that are prone to occur in high-strength prestressed ring beams with ultra-dense steel bars and large cross-sections.

[0006] In order to solve the above-mentioned technical problems, the present invention is achieved as follows: A high performance concrete, characterized in that it comprises the following components by weight: 280kg cement, 80kg fly ash, 48kg mineral powder, 38kg anti-cracking agent, 24kg viscosity reducer, 710kg natural sand, 1065kg gravel, 7.99kg water reducer, 150kg water and 0.235kg cellulose ether.

[0007] The high performance concrete is characterized in that the crushed stones include 16-25 mm crushed stones and 5-16 mm crushed stones, wherein the 16-25 mm crushed stones weigh 745 kg and the 5-16 mm crushed stones weigh 320 kg.

[0008] A method for constructing a steel-intensive concrete prestressed ring beam, characterized in that it includes the following steps: construction preparation → cleaning garbage in the steel mesh (after steel bars are processed and installed) → commercial concrete transportation → concrete layered pouring → concrete vibration → concrete curing and temperature measurement → adjusting the thickness of the insulation layer according to the temperature measurement results.

[0009] The method for constructing a steel-intensive concrete prestressed ring beam is characterized in that the concrete vibration comprises: 1) Use a φ70 / φ50 vibrator, increase the number of vibration points at the corners of the post-casting strips and construction joints, and extend the vibration time. After the concrete is poured, determine the second vibration and finishing time based on the concrete state after it is poured into the mold. The ring beam reinforcement is dense and the horizontal main reinforcement is arranged in an oblique direction, so the vibration is carried out in an oblique direction. 2) Install a flat vibrator at intervals of 600mm on the inclined surface, and open a vibration opening at intervals of 500mm to assist in the vibration of the inclined surface of the ring beam and prevent the upper surface from being loosely vibrated; 3) The height of the large ring beam is 4.3m. When pouring concrete, it is easy to cause concrete segregation when using a sky pump to vertically release concrete. A 300*300 concrete discharge port is opened at an interval of 1500mm at a position of 2m elevation in the middle of the inclined surface, and a 150*150 concrete chute is set at an interval of 2m in the middle of the ring beam during construction to prevent the bottom concrete from segregating. Considering the density of steel bars and the shape of the ring beam, the concrete chute is divided into two sections. In the first section, while the steel bars are tied, the 150*150 square tube is pre-buried obliquely in the middle of the steel bars along the angle of the steel bars. The conduit is about 1m away from the bottom, and the top of the conduit is 50mm away from the concrete surface. When the first section of the concrete conduit is pre-buried, if the steel bars are touched, the steel bars need to be staggered to the left or right. The annular spacing of the bottom conduit is controlled at about 5m. Because it is pre-buried obliquely, the first section of the conduit cannot be taken out later. The second section of the conduit is a trumpet chute at the top, which is connected to the upper part of the first section of the chute when pouring concrete to ensure the smooth flow of concrete.

[0010] The method for constructing a steel-intensive concrete prestressed ring beam is characterized in that: during the steel bar binding process, the vibrating rod guide tubes are pre-buried, and the spacing between the vibrating rod guide tubes is controlled to be about 600 mm, which is convenient for the oblique vibration of the vibrating rod.

[0011] The beneficial effects of the present invention are as follows: It can be seen from the above technical scheme that the present application provides a method for constructing a high-performance concrete and a prestressed ring beam of a steel-intensive concrete, which satisfies the temperature rise control requirements of large-volume concrete by selecting cement with low hydration heat, adding a temperature-controlling anti-cracking agent, and adopting a mix ratio scheme with low adhesive dosage. The mature temperature-controlling and anti-cracking products on the market are selected, and the cement heat release rate is adjusted by using the hydration inhibition principle to slow down the early concentrated heat release of cement, reduce the early temperature stress of concrete, and at the same time, the shrinkage stress of concrete is relieved by using the compensating shrinkage effect, so as to achieve the goal of controlling temperature rise and improving crack resistance. A new viscosity-reducing component is selected, and the filling and compacting effect and lubrication and water-reducing effect of the viscosity-reducing material are used to reduce the viscosity of high-grade concrete, ensure the high fluidity and pumpability of concrete, and improve the strength of concrete under the condition of low adhesive dosage. The negative impact of cement hydration heat is reduced, and the cracking problem of concrete is solved. Compared with the traditional method of adding cooling measures, the invention simplifies the process, improves the construction efficiency, and solves the problem that when the spacing of steel bars is too dense, the internal and surface temperatures can be kept close without adding cooling water pipes, thereby effectively controlling the cracking problem of concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of the plane layout of temperature measurement points for large-volume concrete.

[0013] Figure 2 This is a schematic diagram of the cross section of the temperature measuring points of the prestressed ring beam.

[0014] Figure 3 Schematic diagram of layered pouring. DETAILED DESCRIPTION

[0015] The technical solutions of the embodiments of the present application will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field without creative work based on the embodiments in the embodiments of the present application are within the scope of protection requested by the present application. like Figure 1 As shown: A high performance concrete, which includes the following components by weight: 280kg cement, 80kg fly ash, 48kg mineral powder, 38kg anti-cracking agent, 24kg viscosity reducer, 710kg natural sand, 1065kg gravel, 7.99kg water reducer, 150kg water and 0.235kg cellulose ether.

[0016] The crushed stones include 16-25 mm crushed stones and 5-16 mm crushed stones, 745 kg of 16-25 mm crushed stones and 320 kg of 5-16 mm crushed stones.

[0017] The formula is as follows: Concrete mix ratio (kg / m3) Its performance indicators are as follows: like Figure 3 As shown: A ring beam casting method for a high-performance concrete and steel-intensive concrete prestressed ring beam construction method, characterized in that it includes the following steps: construction preparation → cleaning up garbage in the steel mesh (steel processing and installation completed) → commercial concrete transportation → concrete layered casting → concrete vibration → concrete curing and temperature measurement → adjusting the thickness of the insulation layer according to the temperature measurement results.

[0018] The method for constructing a steel-intensive concrete prestressed ring beam, wherein the concrete vibrating comprises: 1) Use a φ70 / φ50 vibrator, increase the number of vibration points at the corners of the post-casting strips and construction joints, and extend the vibration time. After the concrete is poured, determine the second vibration and finishing time based on the concrete state after it is poured into the mold. The ring beam reinforcement is dense and the horizontal main reinforcement is arranged in an oblique direction, so the vibration is carried out in an oblique direction. 2) Install a flat vibrator at intervals of 600mm on the inclined surface, and open a vibration opening at intervals of 500mm to assist in the vibration of the inclined surface of the ring beam and prevent the upper surface from being vibrated loosely; during the steel bar binding process, pre-embed the vibrating rod guide tube in advance, and control the spacing between the vibrating rod guide tubes at about 600mm to facilitate oblique vibration of the vibrating rod.

[0019] 3) The height of the large ring beam is 4.3m. When pouring concrete, it is easy to cause concrete segregation when using a sky pump to vertically release concrete. A 300*300 concrete discharge port is opened at an interval of 1500mm at a position of 2m elevation in the middle of the inclined surface, and a 150*150 concrete chute is set at an interval of 2m in the middle of the ring beam during construction to prevent the bottom concrete from segregating. Considering the density of steel bars and the shape of the ring beam, the concrete chute is divided into two sections. In the first section, while the steel bars are tied, the 150*150 square tube is pre-buried obliquely in the middle of the steel bars along the angle of the steel bars. The conduit is about 1m away from the bottom, and the top of the conduit is 50mm away from the concrete surface. When the first section of the concrete conduit is pre-buried, if the steel bars are touched, the steel bars need to be staggered to the left or right. The annular spacing of the bottom conduit is controlled at about 5m. Because it is pre-buried obliquely, the first section of the conduit cannot be taken out later. The second section of the conduit is a trumpet chute at the top, which is connected to the upper part of the first section of the chute when pouring concrete to ensure the smooth flow of concrete.

[0020] The following should be noted during the above concrete construction: 1. Reasonable scheduling should be made to avoid long waiting time or insufficient supply of concrete during pouring. The duration from concrete unloading from the mixer to completion of pouring should not be more than 90 minutes, and the longest duration should not exceed 120 minutes. After exceeding the prescribed time, the slump of concrete needs to be re-checked to determine whether it is constructable.

[0021] 2. When the slump loss or segregation of concrete is serious and the working performance of the concrete mixture cannot be restored after taking measures, it shall not be poured into the mold.

[0022] 3. Conduct meteorological surveys in advance and avoid construction in rainy and hot weather.

[0023] 4. Communicate with the mixing station before pouring to the top to appropriately reduce the workability of the last batch of concrete; after pouring to the top and vibrating, if floating slurry is produced, the top slurry should be discharged and another layer of concrete should be poured and vibrated.

[0024] 5. Concrete vibration points should be layered and staggered to avoid local over-vibration.

[0025] 6. Follow-up inspections should be carried out on the concrete pouring process, and relevant quality control records of pouring should be kept.

[0026] 7. When pouring large volumes of concrete not exceeding 1000m3 at a time, the mixing station and the site shall take samples to make no less than 10 groups of concrete strength test pieces respectively, and adopt standard curing and curing under the same conditions respectively.

[0027] 8. Maintenance 1) Before demolding, the temperature difference between concrete curing water and concrete surface should not be greater than 15°C.

[0028] 2) The curing time of the same pouring section should be basically the same, and the moisturizing curing time should not be less than 14 days.

[0029] 3) The demolding process should be carried out continuously and quickly, and the curing material should be covered immediately after demolding.

[0030] 9. Temperature control requirements 1) Raw material temperature control 2) Cement should be prepared and stored in advance, and its operating temperature should not be greater than 50°C.

[0031] 3) The operating temperature of mineral admixtures such as fly ash and mineral powder should not be greater than 40°C.

[0032] 4) After entering the site, the water reducer should be stored in a shaded area and the operating temperature should not exceed 30°C.

[0033] 5) Concrete temperature control The temperature of concrete during pouring should be determined according to the ambient temperature. When the ambient temperature exceeds 30℃, the temperature should be controlled not to exceed 20℃; when the ambient temperature is below 25℃, the temperature should be controlled not to exceed 15℃.

[0034] In hot weather, mixing stations should adopt measures such as ice water mixing, aggregate covering and water cooling to control the temperature of concrete leaving the machine.

[0035] When the ambient temperature is high, insulation and covering measures should be taken for the concrete tank truck, and water should be poured to cool it down.

[0036] Reasonably arrange the concrete pouring time period and avoid pouring during high temperature periods.

[0037] Measures should be taken to lower the temperature of the pouring bin surface before pouring.

[0038] During the pouring process, the tank truck and pump pipe should be wrapped with insulation material and water should be sprinkled to cool them down.

[0039] 6) Structural temperature rise control Temperature monitoring should be carried out when pouring large volumes of concrete.

[0040] The temperature rise of the concrete casting based on the mold entry temperature should not be greater than 50℃.

[0041] The temperature difference between the inside and outside of the concrete casting (excluding the equivalent temperature of concrete shrinkage) should not be greater than 25℃.

[0042] The cooling rate of the concrete casting should not be greater than 2.0℃ / d.

[0043] When removing the insulation cover, the temperature difference between the concrete casting surface and the atmosphere should not be greater than 20°C.

[0044] According to the temperature difference between the inside and outside of large-volume concrete and the requirements for cooling rate, insulation and maintenance measures such as geotextile wrapping, insulation blankets, and spray insulation materials should be adopted on the outside of the formwork. In the event of a sudden change in temperature, insulation measures should be increased.

[0045] Determine the demolding time based on the temperature monitoring results, and the mold maintenance time should not be less than 7 days.

[0046] Cooling measures should be checked and records of concrete temperature control measures should be kept.

[0047] Among them, the temperature monitoring scheme during the pouring process is as follows: The temperature of the ring beam concrete is monitored in real time throughout the entire process to understand the temperature changes of various parts of the concrete casting body and to guide the construction of the ring beam concrete.

[0048] Temperature monitoring point arrangement: like Figure 1 , 2As shown: The ring beam is arc-shaped. The general temperature measurement point takes into account the influence of the structural size and shape. The distance from the outermost temperature measurement point to the concrete surface is 50mm, and the other measurement points are arranged at a spacing of 500mm. The measurement point arrangement is shown in the figure below. The sensor uses a Pt100 temperature sensor and a color paperless recorder for automatic collection. The temperature measurement point numbering rule is A1-1 is the No. 1 measurement point on the first layer of the A axis (numbering direction from the outer arc to the inner arc). The number of temperature sensor measurement points is 297.

[0049] The temperature difference between the inside and outside of large-volume concrete, the cooling rate and the ambient temperature should be tested no less than 4 times per day and night after the concrete is poured. This monitoring scheme automatically measures the temperature once an hour, automatically collects data and updates it in real time. The temperature measurement of the mold should be no less than 2 times per shift.

[0050] The present invention meets the temperature rise control requirements of large-volume concrete by selecting cement with low hydration heat, adding temperature-controlling anti-cracking agent, and adopting a mix ratio scheme with low adhesive dosage. Mature temperature-controlling and anti-cracking products on the market are selected, and the cement heat release rate is adjusted by using the hydration inhibition principle to slow down the early concentrated heat release of cement and reduce the early temperature stress of concrete. At the same time, the shrinkage compensation effect is used to relieve the shrinkage stress of concrete, so as to achieve the goal of controlling temperature rise and improving anti-cracking performance. New viscosity-reducing components are selected, and the filling and compacting effect and lubrication and water-reducing effect of viscosity-reducing materials are used to reduce the viscosity of high-grade concrete, ensure the high fluidity and pumpability of concrete, and improve the strength of concrete under the condition of low adhesive dosage.

[0051] The above are only embodiments provided for the present application and are not intended to limit the present application. Although the present application is described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. However, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A high performance concrete, characterized in that: It includes the following components by weight: 280kg cement, 80kg fly ash, 48kg mineral powder, 38kg anti-cracking agent, 24kg viscosity reducer, 710kg natural sand, 1065kg gravel, 7.99kg water reducer, 150kg water and 0.235kg cellulose ether.

2. The high performance concrete according to claim 1, characterized in that: The crushed stones include 16-25 mm crushed stones and 5-16 mm crushed stones, 745 kg of 16-25 mm crushed stones and 320 kg of 5-16 mm crushed stones.

3. A method for constructing a prestressed ring beam of reinforced concrete based on the high performance concrete of claim 1 or 2, characterized in that: It includes the following steps: construction preparation → cleaning up garbage in the steel mesh and completing steel bar processing and installation → commercial concrete transportation → concrete pouring in layers → concrete vibration → concrete maintenance and temperature measurement → adjusting the thickness of the insulation layer according to the temperature measurement results.

4. The method for constructing a steel-intensive concrete prestressed ring beam according to claim 3, characterized in that: Concrete vibration includes: 1) Use a φ70 / φ50 vibrator, increase the number of vibration points at the corners of the post-casting strips and construction joints, and extend the vibration time. After the concrete is poured, determine the second vibration and finishing time based on the concrete state after it is poured into the mold. The ring beam reinforcement is dense and the horizontal main reinforcement is arranged in an oblique direction, so the vibration is carried out in an oblique direction. 2) Install a flat vibrator at intervals of 600mm on the inclined surface, and open a vibration opening at intervals of 500mm to assist in the vibration of the inclined surface of the ring beam and prevent the upper surface from being loosely vibrated; 3) The height of the large ring beam is 4.3m. When pouring concrete, it is easy to cause concrete segregation when using a sky pump to vertically release concrete. A 300*300 concrete discharge port is opened at an interval of 1500mm at a position of 2m elevation in the middle of the inclined surface, and a 150*150 concrete chute is set at an interval of 2m in the middle of the ring beam during construction to prevent the bottom concrete from segregating. Considering the density of steel bars and the shape of the ring beam, the concrete chute is divided into two sections. In the first section, while the steel bars are tied, the 150*150 square tube is pre-buried obliquely in the middle of the steel bars along the angle of the steel bars. The conduit is about 1m away from the bottom, and the top of the conduit is 50mm away from the concrete surface. When the first section of the concrete conduit is pre-buried, if the steel bars are touched, the steel bars need to be staggered to the left or right. The annular spacing of the bottom conduit is controlled at about 5m. Because it is pre-buried obliquely, the first section of the conduit cannot be taken out later. The second section of the conduit is a trumpet chute at the top, which is connected to the upper part of the first section of the chute when pouring concrete to ensure the smooth flow of concrete.

5. The method for constructing a steel-intensive concrete prestressed ring beam according to claim 4, characterized in that: During the steel bar binding process, the vibrating rod ducts are pre-buried and the spacing between the vibrating rod ducts is controlled at about 600mm to facilitate oblique vibration of the vibrating rod.

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