Abstract: Using engineering examples, this paper summarizes the application of silo slip form construction technology and the experience in solving post-demould maintenance and other issues. Shuangliu Clean Coal Loading Warehouse is located in the northwest of Shuangliu Mine, Liulin County. There are two reinforced concrete circular warehouses with a diameter of 6M arranged in the east-west direction. The eaves height of the warehouse is 35M and the wall thickness is 0.25M. The warehouse is made of frame and brick-concrete structure. Belt machine room, there are reinforced concrete funnels in the warehouse, four in each warehouse, the distance between the two warehouses is 0.5M, a total of 2800 cubic meters of concrete is poured, the foundation is a raft foundation, and the design strength is C25. During the construction process, the base plate and beams were poured and formed at one time. After the mold is assembled, the warehouse body is slid up.
The design strength of the warehouse is C25, and the concrete volume is 945 cubic meters. According to conventional construction, it will take at least 6-7 days and 00 construction personnel. In order to speed up the construction progress and complete the warehouse sliding task before the arrival of the rainy season, it was decided to cancel the original construction plan: () internal lifting method, (2) tower crane method. Because of its limited construction methods and lifting speed, it also consumes a lot of personnel. After many discussions, it was decided to use concrete pumps for vertical transportation of concrete. The original tower crane was only used as a vertical transportation tool for steel bars, iron parts and auxiliary equipment.
After research, it was decided to choose the HBT60A concrete pump. The main technical parameters of the pump are as follows: concrete output pressure 6.3Mpa, concrete output 8.4-67.3 cubic meters. Maximum output distance (pipe diameter 0.M) 00M.
Concrete pump construction is used to lift large volumes of concrete with a height of 30 to 300 meters and a thickness of more than 0.5 meters. It has the characteristics of saving manpower, material resources, short time, high efficiency, fast and convenient, but pumping concrete affects the fluidity of concrete. The requirements are relatively high, and the slump needs to be controlled between 2 and 6 cm. The silo slip form requires that the initial setting and final setting time of the concrete be controlled at about 2 hours and 20 minutes and 3 hours and 30 minutes, which can prevent mold sticking and facilitate slippage. Lift. Although pumped concrete is commonly used in most areas, it is the first time for our company to use the slipform process for silos. How to apply the pumped concrete process to the slipform construction of silos and how to solve the maintenance problem after concrete demoulding? , enhance the strength of concrete and adapt to the sliding speed of concrete. To this end, we take the following measures:
, scientifically and rationally select admixtures to improve the mechanical properties of concrete and improve durability. In view of the wide variety of admixtures on the market, we chose XX-B, XX-BH produced by a factory in Taiyuan City, and XX-BH produced by a certain admixture factory in Shanxi. XX-4, outside Huashen Building Materials, Second Hospital of the Ministry of Chemical Industry
There are many varieties of HS-NF and HS-AF admixtures produced by the additive factory. Using Datong P. 042.5R cement, gravel produced in Liulin (2-4), and water-washed sand produced in Lishi (containing less than 5% mud) were compared and tested. It was found that HS-AF admixture has better adaptability to cement, and the concrete prepared with it The concrete strengths at 3 days, 1 day, and 28 days are 25.5Mpa, 32.8Mpa, and 37.9Mpa respectively, the slump is 3+2, and the initial and final setting times are about 2:20 and 3:30 respectively. Basically, Meet construction requirements. It is determined that the mix ratio of concrete is designed as cement: sand: gravel: water: admixture: 2.6:3.34:0,7. The admixture not only meets the technical requirements of the concrete pump but also meets the requirements of the silo slip. According to the setting time and strength requirements, and at the same time, according to the different dosage of early-strength water-reducing agent, 5-20% of cement can be saved. This alone can save more than 60 tons of cement.
2. The concrete pump requires that the maximum particle size flow of gravel should not be greater than the pipe diameter/3. The pipe inlet slump should be between 2 and 6 centimeters, while the slump of concrete entering the mold should be between 0 and 2 centimeters. Since the tube As the warehouse slide height changes, the pipeline slump loss also increases. The moisture content, mud content, and particle diameter of each batch of gravel and sand are also different. The 24-hour temperature and humidity on site also vary greatly. A major change was made by setting up dedicated personnel to adjust the water-cement ratio at the centralized station, controlling the mix ratio at the construction site to ensure the slump, and setting up iron grates at the inlet of the conveying pump to manually select large pieces of sand, gravel and mud that enter, ensuring It meets the requirements of concrete’s workability, fluidity and setting time, and avoids the phenomenon of concrete separation. In view of the phenomenon that the gravel particles are too small, which may cause the sand slurry to be loosely packed and block cold pipes, the gravel grading should be strictly controlled and the entry of raw materials should be strictly controlled.
3. If the concrete conveying pump wants to have an effective conveying capacity of 60 cubic meters per hour and a conveying height of 60M, it needs to operate continuously. During construction, a centralized mixing station is used for mixing. The feeding is coordinated by a loader. The raw materials are accurately measured and mixed at the centralized mixing station. Combined, the feeding is coordinated by the loader. The raw materials are accurately measured and mixed by the centralized mixing station, and then put into the delivery pump truck tank for secondary mixing so that the concrete can be fully mixed and has good workability. The fixed part of the pumping pipe is a steel pipe that slides up with the warehouse body. Embedded parts are welded every 3m between the two warehouses to fix the steel pipe. Rubber pipes are used in the upper working surface of the warehouse and turned to the east and west warehouses with 90-degree elbows. On the sliding form platform Use a small manual truck to collect the materials, and pour concrete continuously and evenly with each layer of 300mm. When pouring concrete, the direction should be changed in a planned way, that is, the upper layer is poured in a counterclockwise direction, and the next layer is poured in a clockwise direction to reduce the torsion of the warehouse body when sliding up. The steel bars should be tied in place in time to prevent the concrete from being unable to continue working. The phenomenon of pipe blockage. During the handover between two shifts, pumping should be performed every 5-20 minutes depending on the temperature to prevent pipe blockage.
4. In the past, the high-altitude maintenance of thin-walled warehouses used the watering method of hanging straw bags, which is labor-intensive and labor-intensive, and it is easy to form water marks on the surface of the warehouse during watering, which affects the appearance. Therefore, the HS-4 concrete curing spray method is used. . This agent is mainly composed of organic matter and compounded with other inorganic silicates. It is non-flammable and non-corrosive. When the curing solution is sprayed on the concrete surface, the calcium hydroxide reacts with the silicate in the curing solution to generate calcium silicate and hydroxide. Silicates are insoluble substances that can seal the gaps on the concrete surface and form a solid The thin film prevents premature evaporation of free water in concrete and can effectively prevent temperature difference cracks.
During construction, after the concrete surface has been plastered and roughened, and there are no water stains on the surface (after the concrete has initially set), arrange for a dedicated person to spray the curing agent on the concrete surface with a high-pressure sprayer. The nozzle should be about 30cm away from the concrete surface. When spraying, the staff should stand upwind. Spray forward in sequence, row by row. When using it for the first time, consider that the operator is unskilled to avoid spray leakage. You can spray twice (the interval is about one to two hours, once horizontally and vertically). Once you are skilled, you can spray once.
Through the above measures, we used delivery 5 axis cnc machining pump impeller to lift concrete in Shuangliu Silo, used tower cranes to lift auxiliary materials and steel bars, and introduced new processes and methods such as early-strength agents and curing agents. This not only saved a lot of cement, but also reduced project costs. It accelerated the progress and established a new image of the company. appears in:
, In terms of safety, due to the use of transfer pumps, the number of workers under the warehouse has been reduced. In the past, winches were used to lift 0 people/shift under the warehouse, but now there are 2 people under the warehouse, which avoids the harm to people below the warehouse due to cross-working and debris falling on the warehouse. No safety accidents occurred during this construction.
2. In terms of project quality, the slump and mix ratio of concrete should be controlled, the sand and stone ratio should be appropriate, the water-cement ratio should be normal, the tamping should be dense, the steel bar binding spacing should meet the requirements, and the raw materials should be strictly controlled, especially the secondary installation of the concrete delivery pump. Stirring and increasing the workability of concrete are difficult to achieve in previous construction. The depth of each pouring is 300mm, and the time interval is basically the same. The concrete does not appear to be stratified. The vibration and compaction and the use of curing fluid have solved the hidden quality risks caused by incomplete concrete curing. After Party A’s on-site inspection, the quality of the project fully meets the requirements. The project has been well received many times during the acceptance inspection organized by the relevant superior departments.
3. In terms of economic benefits, this construction requires 80 people and the construction period is 0.5 days. If the labor cost is 30 yuan/labor, the direct cost will be;
Regular legal labor costs are: 6 days * 00 people * 30 yuan / person = 48,000 yuan
The labor cost of the pumping method is: 0.5 days*80 people*30 yuan/person=25,200 yuan
Save cement (Datong) 60 tons * 440 yuan / ton = 26,400 yuan
Save direct costs: 49,200 yuan
In the silo slip form, we also found some shortcomings, such as: the lagging of steel bars affects pouring, and the waste of steel joints is large. If the pressure welding process is used, the effect will be better. 2. The concrete delivery pump should use a stirring rod on the warehouse to shorten the concrete pouring time.
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