The application of the “jumping method” in the construction of concrete flooring above ground
The application of the “jumping method” in the construction of concrete flooring above ground
: The jumping method is the “resistance and release” characteristic principle that the concrete’s performance has not been stable during 5 to 10 days before the performance of the concrete has not stabilized during 5 to 10 days, and it is easy to release the internal stress.
It is to divide the building foundation or large -scale concrete plane mechanism into several areas, and pour one by one.
This article summarizes the operation points, equipment requirements, quality control, and safety measures of the jumping method through the first application of the jumping method from the jump method.
The floor size of the floor of the 7.885M elevation of the Terminal of Guiyang Longdongbao International Airport mentioned in the article is 255m × 115m, which is a ultra -long and ultra -wide concrete structure. The construction period is shortened by the construction of the jumping method, saving costs saving costs, saving costs Successful cases have proved the advancement and feasibility of the construction of the jumping method.
Guiyang Longdongbao International Airport Expansion Terminal Project 7.885M is a high floor. The axis size is 255m × 115m, which is a ultra -long and ultra -wide concrete structure. Structural overview: The beam is a pre -stress for bonding, see the tension -end distribution in the figure; the inside of the board is a non -bonding prestigious power board, see the horizontal direction shadow distribution in the figure; The distribution of the rear pouring band. It can be seen from the figure that when the prestress is separated in the same pull section, when the rear pouring band is not closed and the design intensity is not reached after closed, the prestressed stress cannot be carried out.
In view of the above reasons, the “jumping method” construction is adopted for the large -scale floor concrete structure, and the pouring band is canceled. The prestressed tension is carried out 60 days in advance. By using the “jumping method” construction, it has achieved a good effect of shortening construction period and saving construction costs.
Figure 1 The distribution of pouring bands
1 The scope of applicable to jumping method
This work method is suitable for the construction of various large and long concrete flooring. It is especially suitable for projects that are short and large in area, and various processes are inserted.
2 Construction process process
See Figure 2 for details of the process.
3 Operation points
3.1 Division of floor floor warehouses
The structure of the ultra -long floor is divided by the appropriate size. Generally, the edge length of each warehouse is between 45m to 60m.
The factors that need to be considered when dividing are:
1) The minimum impact on the structure, the seam joints are generally set in the minimum structural shear;
2) According to the one -time pouring capacity of the concrete at the scene, the area of the warehouse should not be too large.
3) The requirements of other professional construction should be considered to avoid the construction of other majors due to the requirements of the separation time of the warehouse.
3.2 Fixed order of pouring
A reasonable pouring process of each warehouse to reduce the production of the contraction of the structure of the concrete structure and the superposition of the overall concrete structural contraction stress. Based on this, the overall deployment of the construction process is based on the requirements of other professional construction. The order of the pouring of each warehouse and the last overall closure time and the temperature of the warehouse.
There are two original principles in the order of each warehouse:
1) The adjacent warehouse interval can be connected at least 7 days after the interval;
2) Follow the longest direction of the structure as a whole. The pouring order of each position can be basically carried out in the middle of the middle and then the middle. The pouring warehouse on both sides of the pouring is finally poured in the middle warehouse reserved in a suitable time. If it is difficult to reserve the middle warehouse, it can be carried out according to the “middle and back sides”, and directly pour the pouring to both sides from the middle.
3.3 Sub -warehouse seam isolation network installation
① The jumping warehouse can be used at the construction gap between the fast -ends, or the stainless steel wire collection network can be used.
② Using the fast -collection network to be poured in the concrete 1 day, the fast -ends of the pouring warehouse edge must be removed for 1 day to ensure the adhesion of the new and old concrete.
When pouring the neighboring warehouse, the concrete is used to divide the wet warehouse seam, and then the second concrete pouring is performed.
3.4 Determination of concrete performance, material, and cooperation ratio
The amount of material dosage can be referred to the following experience data:
1) For C40 concrete cement, the amount of concrete cement should be less than 290 kg, and the amount of C30 concrete cement should be less than 260 kg;
2) Single -mixed powder coal should be 15-20 % or compound mixed with 20 % powder ash and 10 % slag powder;
3) The total amount of C40 concrete gel material should be less than 390 kg, and the total amount of C30 concrete gel material should be less than 330 kg;
4) C40 concrete water volume should be less than 165 kg, and the amount of water for C30 concrete should be less than 170 kg;
5) Polycarboxylic acid water reduction agent, C30 ～ C35 should be 0.8 %, C40 should be 1 to 1.2 %;
6) The amount of aggregate should be greater than 1110 kg, and the amount of fine aggregate should be greater than 750 kg;
7) The scene of the floor concrete of the floor should be controlled at 12 ± 2, the initial condensate time is controlled for 5 to 6 hours, and the final condensation time is controlled at 7 to 8 hours.
3.5 Key points for controlling the concrete pouring process
① Determine the reasonable pouring process according to the site of the pouring warehouse floor. The overall pouring direction is the long side of the pouring block to advance from one end to the other to facilitate spraying, light collection, and coverage of the water connection.
② After the concrete enters the mold, it is required to be sprayed to maintain it. When the wind speed at the scene is large, it is advisable to set up a height of 3 to 4m around the pouring warehouse.
③ Perform the second or third through the artificial pressure, glow and light machine collection work before and after the concrete. When the watering area is large, the last time the light collection work is carried out, and the work of covering the film and grass bags is covered. Essence
3.6 Key points for maintenance process control
① For the floor with a layer of film and a layer of straw bags to keep the heat preservation, moisturizing and sprinkling for 15 days, the film is covered with moisturizing effect, and the grass bag is shade and water storage.
② After 15 days of sprinkling water, the covered straw bag was set off, but the film should be kept as long as possible to reduce the development of dry and contraction in the later period.
③ Before the floor concrete was poured 24h, it can be limited to preparations for measurement, positioning, and bullet lines. At most, it only allows dark -column steel welding work, and unloading bulk materials is not allowed to avoid impact vibration. After 24 hours, you can first arrange a small number of small batch of dark columns and shear wall steel bars for lingering activities in batches, so as to lightly unload and play to control and reduce impact vibration power. On the 3rd day, we can start to unload the materials such as steel pipes and engage in normal modeling construction.
4 Materials and Equipment Requirements
The variety and dosage of cement are important factors that affect the performance of concrete and concrete temperature deformation, self -shrinking deformation, dry shrinkage deformation. When choosing cement, we should comprehensively consider the labeling of the cement, the mineral composition of the cement clinker, the size of the water, and the fineness of the cement. More than 60 ° C. Other quality indicators shall comply with the current national standard “General Silicate Cement” GB175-2007.
When selecting fine aggregate, it should be considered from the perspective of the average particle size, fineness mold number, granular level and sand rate of the fine aggregate. The ideal sand is high quartz content, round particles, clean, smooth sieved lines, thin degree modulus between 2.8 and 3.6, the average particle size is 3.8mm, mud containing (or stone powder volume) is less than 1.5 %, muddy mud The block content of the block is less than 0.5 %. Other quality indicators shall meet the requirements of the JGJ52-2006 requirements of the “General Sand, Stone Quality and Inspection Methods”.
When choosing coarse aggregates, we should consider the variety, mechanical properties, grade matching, granular shape, mixed quality, mud content, and water absorption rate. The ideal coarse aggregate is 5-40mm continuous granation with granite fragmented and crude material. The mud content of coarse aggregates is less than 0.5 % and the content of mud blocks is less than 0.2 %. Other quality indicators should meet the “ordinary concrete sand, stone quality and inspection Method Standard “JGJ52-2006 Requirements.
4.4 Mixing material
After mixing the ash into the concrete, it can reduce hydration heat, reduce dry shrinkage, and improve the ease of mixing concrete, but the early intensity is low. It is advisable to choose second-level powder coal ash with good performance and various indicators that meet national standards. The CAO content does not exceed 10%. Other quality indicators should meet the requirements of GB/T1596-2005 for “Flore and Coal ash for cement and concrete”. According to the needs of the project, the amount of flour ash is determined.
The development law of hydration and heat after mixed with slag powder is similar to mixing powder and coal ash. The slag powder should be used with dual -mixed with powder and coal ash, and the doped amount should not exceed 50 % of the amount of cement during dual doping. The various indicators of slag powder shall meet the requirements of GB/T18046, which are used in the Gab/T18046 for the GB/T18046 of the “Pinerium Polarized Polarization Stab Powder in cement and concrete.”
4.5 water reduction agent
The water reducing agent should adopt a polycarboxylic acid reducing agent that complies with the national standard “Polycarboxylic acid System” JG/T223-2007. The amount of C30 to C35 is 0.8 %, and the C40 controls 1 to 1.2 %. When using polycarboxylic acid, you must pay attention to the sensitivity of polycarboxylic acids. The tankers loading with polycar carboxylic acid cannot be mixed with the tanker carrier -loaded water reducing agent, and the compatibility of polycarboxylic acid and cement and mixture.
5 benefit analysis
1) Because the waiting time of closed bands after construction and the waiting time of the intensity of concrete intensity after the construction of the band and the rear pouring band can greatly shorten the construction period. Especially for projects with pre -stress, it can make prestressed projects advance in advance and thus thus thus there. Shorten the entire construction period.
2) On the basis of shortening the construction period, the construction cost of the entire project has greatly saved a great effect.
3) It can well control the early cracks and later cracks of the floor, save the cost of crack governance and get good social benefits.
The “jumping method” has achieved more mature experience in underground projects. The above -ground projects should be applied as appropriate according to the shape, size and climate environment of the building, and the level of construction management. The kind of structure is considered as a distance of 30-40 meters as long as the structure concrete is divided into a distance of 30-40 meters. Pouring the “jumping warehouse” can avoid the shrinkage of the concrete, which is very one -sided and superficial.
The “jumping method” is a comprehensive technology. It is necessary to summarize the control points and difficult points at each stage to take corresponding measures in order to make the “jumping method” achieve no harmful cracks and less harmless cracks.
The successful case of the ground structure application of the expansion project of Guiyang Longdongbao International Airport has given great reference and encouragement to the construction of large -scale concrete construction in the future. At the same time The progress of optimization is particularly important, and it is also necessary to pay attention to the construction of the jumping method.
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