How to pour a concrete project that is 4 meters thick, 20 meters wide, and 70 meters long? ?

Concrete that is 4 meters thick, 20 meters wide, and 70 meters long cannot be made into one piece, right?

It doesn't matter if it's a whole, make sure: (1) Concrete pouring plan ； (2) Concrete pouring volume per hour ； (3) The time required to complete the entire pouring work. Just follow this plan and you’re done!

It is better to pour in layers and sections. If too much and too thick are poured at once, it will be difficult to control.

This is mass concrete pouring. main control: Pouring speed, delivery pump layout point, setting of concrete temperature measurement point, mixing ratio of anti-cracking agent, and selection of low hydration heat cement. If the control is not good, temperature stress will easily occur and concrete will crack. If the pouring sequence is not well controlled, cold joints may easily occur. During construction, large-volume concrete needs to be prepared with special plans and key controls.

It's big enough, but the most important thing is to have a detailed construction plan, unified command and unified dispatch, and enough pouring machinery, transportation capacity, castables, water sources, electricity, manpower, technology, etc. to formulate emergency plans.

Just after registering, I came up and asked such an unclear question. Are you cheating? ?

According to the mass concrete construction plan: The foundation of this project is a raft foundation with a plate thickness of 1.4m and a concrete strength grade of C40, which is a typical mass concrete. The construction of this kind of large-volume concrete base plate has the characteristics of high hydration heat, large shrinkage, and easy cracking. Therefore, the pouring of large-volume concrete base plate should be taken seriously as a construction focus and difficulty. The focus of mass concrete construction is to minimize the adverse effects of temperature stress and prevent and reduce the occurrence and development of cracks. Consider taking the following construction measures: 1. The material cement is preferably ordinary Portland cement, and the coarse aggregate is gravel or pebbles with a particle size of 5 to 30 mm, a mud content of ≤1%, good shape, hard texture, no more than 10% of slender and flaky particles, and no weathered particles. The fine aggregate is medium sand, with mud content ≤1%, uniform and clean color, fineness modulus controlled at around 2.7, and sand rate of 30 to 45%. The expansion agent uses UEA-M composite expansion agent to compensate for shrinkage. Select high-quality Grade I fly ash with small fineness, light color, low carbon content and stable quality and lignocalcium water-reducing agent to reduce the early hydration heat and enhance the later strength. 2. There are 2 towable pumps at the construction site of machinery and equipment, and each concrete pump is equipped with 4 high-frequency vibrators. Equipped with 10 concrete mixer trucks. 3. Construction points 3.1 Selection of concrete mix ratio: 3.1.1 The mass concrete mix ratio can be determined by referring to the table below or by trial mixing in the laboratory. concrete strength grade: C35, P8 water-cement ratio 0.5 sand rate 37% Material name cement sand stone water fly ash UEA-M dosage per cubic meter (kg) 320 710 1208 163 55 30 (8%) 3.1.2 According to the specification requirements, the cement dosage per cubic meter of concrete is ≤550kg. The heat of hydration is controlled at T3D≤230kJ/kg, T3d≤270kJ/kg. The total effective alkali content in concrete is less than 5kg/m3, and the chloride ion content is ≤0.06% of the cement weight. 3.1.3 Temperature stress calculations should be carried out during construction. The maximum temperature rise of concrete hydration heat should be controlled below 50°C, and the molding temperature of large-volume concrete should be strictly controlled below 18°C. 3.1.4 In order to meet the requirements of pumping and construction operations, the concrete slump is required to be 160~180±20㎜. 3.1.5 In order to ensure the horizontal flow of the foundation floor and the three-dimensional intersection construction, the concrete is required to meet the initial setting time of 3 to 4 hours. 3.2 Transportation requirements for concrete: 3.2.1 The time when concrete is transported from the centralized mixing station to the site shall not exceed 0.5 hours, and water addition is strictly prohibited during this period. 3.2.2 After the concrete arrives at the construction site, samples must be taken to measure the slump. If the slump does not meet the requirements for pumping, add a high-efficiency water-reducing agent according to the mix ratio requirements. Adding water is strictly prohibited. 3.2.3 The concrete mixer truck must complete pumping within 1 hour after arriving at the construction site. 3.3 Mass concrete pouring: 3.3.1 Divide the large volume of concrete into working areas of roughly equal area, and pour the concrete on a stepped slope according to the working area. 3.3.2 When pouring in each working area, the pouring sequence must be strictly controlled. The pouring method is to use segmented fixed points, one slope, layered pouring, sequential advancement, and one-stop pouring to the top. 3.3.3 The concrete pouring proceeds according to the layered downslope. There are two rows of vibrators at the front and back. The front row of vibrators vibrates the concrete at the pouring point, and the rear row of vibrators vibrates the concrete at the slope. At the corners of the components, vibrating templates are used to solve the honeycomb pitting on the surface of the components. The distance between the insertion points of the vibrator should not be greater than 40cm, and should be inserted into the lower layer 10cm. The vibration time for each hole should not be less than 10 to 15s, and should not exceed 30s, subject to the concrete being slurry and not bubbles. The vibrator should be inserted quickly and pulled out slowly to make the concrete fully dense to ensure the compactness of the concrete. 3.3.4 In order to prevent plastic cracks from appearing on the surface of large-volume concrete, after the pouring is completed, it is pressed and formed in three times, and the surface is smoothed with an iron trowel in the last time. The entire process is ensured to be completed before the final setting of the concrete. 3.3.5 When the concrete structure has a post-poured belt, after the concrete strength on both sides of the post-poured belt reaches 100%, the post-poured belt should be poured with concrete of a higher strength grade and mixed with 15% UEA-M composite expansion agent. 3.3.6 Concrete test blocks are retained. The test blocks are sampled on site and produced on site. One group is taken according to 100m3 of each working area. At the same time, the same group of test blocks as on site is also left in the concrete batching station to facilitate detection and problem finding. 3.4 Maintenance of mass concrete: 3.4.1 After the final plastering of the concrete, it should be removed and covered with plastic sheeting, straw bags or cotton felt to prevent the concrete surface from shrinking and drying due to excessive water loss due to high temperatures, so as to achieve the purpose of thermal insulation and moisturizing. The curing time should be no less than 28 days. 3.4.2 After the side wall concrete is poured, pour water directly on the formwork for curing. After removing the formwork, cover it with a layer of plastic film in time, and hang sack sheets on the film to protect it from water. The curing time shall not be less than 28 days. 3.5 Temperature measurement of large volume concrete: 3.5.1 Calculation of mass concrete temperature During construction, crack prevention and impermeability are the dominant construction principles. The design uses C35 and P8 impermeable concrete, mixed with high-efficiency composite expansion agents. The concrete is pumped from a centralized concrete mixing station. Concrete surface insulation uses two layers of straw bags and a layer of plastic film underneath. The theoretical mix ratio is: Ordinary silicate 42.5 grade cement 320kg/m3, admixture 30kg/m3. The internal temperature will reach the highest three days after slab concrete is poured, so the temperature difference of concrete is calculated using the temperature difference of three days. 3.5.2 The temperature measurement adopts the method of pre-embedding the bottom-sealed steel pipe in the plate. The embedding depth is 40cm from the bottom of the plate and 20cm from the top of the plate. The temperature is measured with a portable thermometer. 3.5.3 Temperature measurement content: Record the temperature of concrete entering the mold, the atmospheric temperature when entering the mold, the curing temperature, and the temperature difference between the inside and outside. 3.5.4 Temperature measurement time interval: Measure every 2 to 4 hours from 1 to 5 days ； Measure once every 4 to 8 hours from 6 to 10 days ； Measure once every 12 to 24 hours from 10 to 15 days. Strictly control the temperature difference between the inside and outside of the concrete to not exceed 25°C. 4. Comprehensive measures to prevent concrete cracks 4.1 Measures to prevent cold joints 4.1.1 Ensure the continuous supply of concrete, and the pouring time of each layer shall not be less than its initial setting time. 4.1.2 Layered pouring in blocks a. When the area of ​​the component is small and the pouring time of each layer of concrete is within 2 to 3 hours, each layer should be poured in one go. ； In order to reduce the restraint stress, the foundation floor is poured in two sections along the length direction, leaving an 800mm wide post-pouring belt in the middle to form a ring to reduce the shrinkage length and restraint, so as to facilitate the release of early and mid-term temperature stress. After the shrinkage of the two sections is mostly completed, the post-pouring belt is poured and densely filled with semi-dry hard fine stone concrete of one strength level higher. Concrete is poured in two steps for each section of bottom plate. This method adopts longitudinal division and upper and lower layering, which is conducive to layer heat dissipation, reducing restraint effects, and releasing temperature shrinkage stress. b. When the component area is large and the pouring time of each layer cannot be completed within 2 to 3 hours, use layered slope reduction and vibration to naturally form a slope. The horizontal construction joints are located 350mm away from the bottom plate, and steel plate waterstops are used for the horizontal construction joints. The pouring and pounding sequence is shown in the figure below. 　　 c. When the concrete mixer and transportation machinery malfunctions or other unexpected situations occur, the thickness of each layer of concrete pouring should be reduced to prevent cold joints. 4.1.3 Measures to control temperature cracks (1) Reasonably select the mix ratio to reduce the heat of hydration temperature. Gansu lacks low-heat cement and uses higher strength grade ordinary cement with high heat of hydration temperature. For this reason, large-size coarse aggregates are used, the sand and stone gradation and mud content are strictly controlled, and wood is added to the concrete. Calcium water-reducing agent and fly ash are used to optimize the concrete mix ratio to reduce the amount of cement to 320kg/m3 and reduce the temperature rise of hydration heat. At the same time, about 10% of stones are added to the concrete when pouring the base plate, which not only saves concrete, but also absorbs heat and reduces the temperature rise of hydration heat. (2) Reduce the temperature of concrete entering the mold. In order to reduce the pouring temperature, methods such as adding an appropriate amount of ice chips to underground low-temperature water, cooling by sprinkling gravel, and covering the surface with sand are used to reduce the mixing temperature and shorten the concrete transportation time as much as possible. Add lignocalcium retarder to the concrete to extend the initial setting time to more than 6 hours, slow down the pouring speed, and thin-layer pouring. Ventilation fans are forced to ventilate to speed up the dissipation of heat during the pouring period, delay the peak of hydration heat, and extend the concrete heating period. (3) Appropriately configure temperature structural steel bars for structural thin layers and stress-concentrated parts, add Ф12 fine steel mesh, and appropriately add structural steel bars at stress-concentrated parts around the opening to disperse stress. (4) Control the form removal time. According to the temperature measurement results, if the difference between the surface temperature or atmospheric temperature of the concrete after the form is removed and the internal temperature of the concrete is less than 25°C, the form can be removed. ； If the difference between the reduced surface temperature or atmospheric temperature and the internal temperature of the concrete is greater than 25°C, not only cannot the formwork be removed, but insulation measures should be taken to cover the formwork with insulation material to reduce the temperature difference. (5) Strengthen the curing and insulation of concrete a. The side formwork of the base plate is lined with a layer of 80mm thick plastic foam insulation board to reduce the temperature difference on the side of the concrete. b. After the concrete is poured, early wet curing is carried out. The bottom plate is cured by water storage in the enclosure. After the formwork is removed, it is covered with a layer of plastic film in time, and two layers of straw mats are added on the film for insulation to reduce the temperature difference between the inside and outside of the concrete. Keep the difference between the core temperature and the surface temperature of the concrete at about 25°C to increase the early elastic modulus and enhance crack resistance. c. Avoid the combined effect of cooling and drying shrinkage of large-volume concrete. Cooling and drying shrinkage of large-volume concrete occur at the same time, resulting in stress accumulation, which is one of the main reasons for cracks in the later period. For this reason, after the concrete is removed from the formwork and cured, the soil is immediately backfilled to raise the groundwater level by 2/3 of the total height. The entire foundation floor is kept moist to prevent excessive dehydration, drying, shrinkage and moisture in the concrete during the cooling period.

I have just completed a similar concrete pouring project. There is no layering and segmentation. I mainly add some cooling coils inside the concrete and use external cooling water to force circulation to cool the internal hydration heat of the concrete. For other methods, follow the method on the 8th floor.

I have worked on a compressor foundation before. It is not as big as the foundation you mentioned, but it is not small. It also uses coil circulating water for cooling. I totally agree with what everyone said above, and please pay attention: 1. The time and season of construction. If it is the rainy season, pay attention to the location of the pump station. The construction site conditions are poor and the pump station is not in position due to muddy conditions. 2. No matter what cooling measures are adopted, there must be procedures (design and supervision approval). 3. Make plans for various unexpected situations that may arise, such as: The commercial mixer could not arrive in time, the pump truck broke down, it rained heavily, the steel stirrups collapsed, the cooling coils were crushed by concrete, the vibrator broke, there was a sudden power outage, etc. The construction of large-volume concrete foundations is difficult, but I have never heard of 4-meter-thick concrete foundations. Can you explain it in detail? It will also open your eyes and gain insights!