Cast-in-place hollow GZ polymer alloy composite mandrel
Development and application of floor structure
Xie Dajiang Cheng Rong Zhi
(Hunan Xiangtan Xiangtan Planning and Architecture Design Institute 4 1 100)
Based on the system engineering principle and system analysis method, combined with engineering application examples, this paper systematically discusses and deeply operates the research and development of GZ polymer alloy composite core mould in cast-in-place concrete hollow floor structure technology. It provides engineering practice experience for construction technology and construction quality control.
Keywords: GZ polymer alloy core mold tile snap-button movable bracket
1. Introduction
GZ polymer alloy core mold has the advantages of high strength, good toughness, light weight, no water absorption and easy long-distance transportation. It is an internal mold without core pulling for cast-in-place hollow floor, and its application in cast-in-place hollow floor and core mold is very mature abroad, but the innovation and application of internal mold without core pulling for cast-in-place hollow floor in China is still a subject to be further studied.
Cast-in-place reinforced concrete hollow floor technology is a kind of floor structure system that has been developing continuously in China in recent years. Therefore, both in design and construction are constantly being developed and applied. As far as core molds are concerned, there are generally corrugated thin-walled steel pipes, paper pipes, rigid plastic pipes, high-strength composite thin-walled concrete pipes and GZ polymer alloy composite core molds in China. These core molds are all embedded internal molds that make holes in the cast-in-place reinforced concrete hollow floor, which plays a very important role in the research and application of cast-in-place hollow floor. However, corrugated thin-walled steel pipes, paper pipes and rigid plastic pipes have not been widely used in the application of hollow floors because of their high prices, and they are mostly used in concrete at present.
Development and characteristics of polymer alloy composite mandrel in 2.2.GZ
In the research and development of cast-in-place reinforced concrete hollow floor, the price of core mould and various technical indexes determine the cast-in-place
Development direction of popularization and application of reinforced concrete hollow floor. After two years' efforts, GZ polymer alloy composite core mould was successfully developed by Hunan Xiangtan Sepp New Material Manufacturing Co., Ltd., which was made of polymer materials and recycled waste plastics as main raw materials, and was assembled by extrusion, injection molding and pressing. It played a significant environmental protection role in controlling "white pollution" in China and won a national patent (patent number ZL 0322 7465438+).
2. 1. Lighter weight and thinner wall thickness. Through the end sealing plate, movable support intermediate bracket and end partition plate, the core mold has the strength and rigidity to meet the construction requirements.
2.2. By connecting the tiles with the buttons, you can flexibly form cores with various geometric shapes (see figure 1).
2.3. Adopt industrialized production to improve production efficiency and ensure product weight.
2.4. Using overlapping transportation greatly reduces the transportation cost.
2.5. Using recycled waste plastics as the main raw material provides an effective way for recycling waste plastics and has obvious environmental benefits.
The core mold meets the construction requirements in technology and the market requirements in price, and has the basic conditions for wide application in domestic and foreign markets.
3. Engineering application examples
GZ polymer alloy composite core mould is applied to cast-in-place concrete hollow floor structure technology, including prestressed hollow floor. In many large-span building projects, such as Xiangtan Municipal Committee Building (span 12 m), Xiangtan Mengzeyuan Complex Building (span 14m) and Xiangtan Special School Complex Building (span 12m), the thickness of floor slab and the size of core mould increase accordingly. These include:
Xiangtan Municipal Committee Building 2 1 Floor, Central Hall 12m×24m. In order to ensure the clearance and overall space effect, the third to nineteenth floors of this part adopt hollow floors with a thickness of 450㎜, the GZ polymer alloy mandrel is D350㎜ (upper circle and lower circle), and the pipe length L is less than or equal to 1 000 mm After careful analysis,
3. 1. Process flow and operation points
3. 1. 1 Flowchart (see Figure 2)
3.2 Key points of operation
3.2. 1 Construction preparation: Make clear the model and technical parameters of the mandrel according to the design drawings, draw up the specification sheet, and place an order to purchase the mandrel.
3.2.2 Measuring and setting out, preparing axis extradition and formwork support.
3.2.3 Formwork shall be calculated and determined according to the stress state, and the formwork supporting materials and methods shall be determined.
(1) formwork installation shall comply with the provisions of formwork sectional works in Code for Acceptance of Construction Quality of Concrete Structure Engineering (GB50204-2002).
(2) The beam-slab formwork of cast-in-place concrete hollow floor shall arch according to the design requirements; When the design has no specific requirements, the springing height should be 2/ 1000 ~ 3/ 1000 of the span of one-way slab or two-way slab.
3.2.4 Elastic line positioning: according to the design drawings, pop up the position lines of core formwork and concealed beam, steel bar distribution line and embedded position line of hydropower installation pipeline on the flat die.
3.2.5 Binding steel bar at the bottom of the slab: according to the mark of bullet line in the figure, bind the hidden beam first, and then bind the steel bar at the bottom of the slab. The steel bar at the bottom of the slab shall be provided with a cushion block with a thickness of15 mm.. Then tie the anti-floating iron wire (see Figure 3 and Figure 4).
TT-is the thickness of the top of the plate.
Tb refers to the thickness of the bottom of the board.
D is the diameter of the spindle.
Hs- is the thickness of the floor.
D+bw-mandrel spacing.
3.2.6 Embedding: Water and electricity are installed through floor concealed pipes or embedded steel sleeves, and fixed in corresponding positions by spot welding.
(1) During the construction process, the reserved and embedded work in the installation project must be carried out in parallel with the processes such as steel bar binding and core mold placement, otherwise it will be difficult to insert.
(2) The embedded horizontal pipes should be arranged as far as possible between the ribs of the plate and at the hidden beams. When horizontal pipes, wire boxes, etc. It is unavoidable to disconnect from the spindle, and the spindle tube can be disconnected. In the case of pipeline crossing or special concentration, mandrel pipe with smaller diameter can be used to avoid it.
(3) The vertical pipes passing through the floor shall be embedded with steel sleeves, which shall be welded and positioned firmly with the steel skeleton according to the cross position. The allowable deviation of the center should be controlled within 3mm, and it is forbidden to pick afterwards. The clear distance between the steel sleeve and the mandrel should not be less than 50 mm.
4.2.7 Binding the steel mesh between ribs: During construction, it should be marked according to the elastic line in the drawing, and measures should be taken to prevent the steel mesh from bending and deforming during handling, stacking and hoisting.
3.2.8 Placement of mandrel: After the bottom bar and the positioning bar at the bottom of the network management are bound and spot-welded, accurately place the mandrel according to the requirements of elastic line. See (figure 1. Figure 2. Figure 3) Learn more about mandrel placement.
Attention should be paid to during installation:
(1) According to the floor structure size and hoisting construction conditions, the core formwork should be fabricated in sections and then installed as a whole, with its main size ≤ 1000㎜.
(2) In the process of loading, unloading, stacking and lifting, handle with care, and it is forbidden to throw to prevent damage. When hoisting in place, a special hanging basket should be made and unloaded to the construction site.
(3) In the process of placing the mandrel, technical measures should be taken to ensure its accurate position and overall straightness, so as to ensure the geometric size of concrete between the hollow slab rib and the upper and lower slabs. When placing the mandrel, the bottom should be padded with concrete pads or stays, and the ribs between the mandrel should be welded with transverse stays for positioning. The overall straightness deviation of mandrel placement shall not exceed 2.5/ 1000, and the maximum deviation shall not exceed15mm2.
(4) In the process of placing the mandrel, the scaffold board shall be laid at any time to protect the finished steel bar and mandrel, and direct trampling is strictly prohibited. When the mandrel is damaged before the board gluten bonding, it should be completely removed and replaced; When the board gluten has been bound and the mandrel is damaged in a small area, plugging measures such as filling sacks and sticking tape paper should be taken.
3.2.9 Binding plate reinforcement: After the binding of bottom plate reinforcement and mesh, core formwork placement and reserved embedment are all completed, the floor reinforcement and negative reinforcement supported by the bottom plate are bound (the above processes can make the bottom plate, plate surface and ribs form a whole).
Anti-floating measures
(1) When placing the mandrel, confirm that the bottom of the mandrel has been padded to the design elevation, and the spacing and clear distance between the mandrel and the concealed beam meet the design requirements, so anti-floating technical measures can be taken.
(2) Installing and fixing the mandrel: In order to ensure the accuracy of the placement position and elevation of the mandrel, the mandrel can be placed on the die base; When concrete is poured and rammed, the vibration of concrete will produce buoyancy to the core mold, so the core mold is vertically fixed between the core mold and the steel bar on the board with mortar pad.
3.2. 1 1 Cast concrete: determine the concrete mixture ratio according to the design requirements.
(1) Before pouring concrete, in addition to the quality inspection and acceptance of steel bars and reserved embedded parts, the installation of core formwork and anti-floating measures should also be inspected and accepted, and concrete can be poured only after it meets the specified requirements. When pouring concrete, the core mould should be observed and maintained, and when the position of the core mould deviates, it should be corrected in time.
A, this project adopts the construction method of on-site mixing and concrete pump transportation. The concrete pouring sequence of floors is shown in Figure 5.
B, construction service road:
In this project, a dedicated overhead 150mm construction sidewalk is set up on the floor, and colored strips of cloth are laid under the transportation road to prevent secondary pollution during concrete pouring. Concrete pumping pipes shall not be placed directly on steel bars and mandrels.
C, considering the design width of the rib is 60mm, the pebble size in the mixture ratio should not be greater than 3 1.5㎜.
D, concrete cloth, vibrating should be synchronized, concrete cloth should be evenly blanking on both sides of the mandrel, relative vibration. Φ 30 vibrator is used in the construction (Figure 6).
E, the concrete within the scope of this beamless floor requires one-time molding, and no construction joints are allowed.
F, in the process of cast concrete, construction personnel shall not directly trample reinforcement and mandrel.
3.2. 1 1 concrete curing: concrete curing adopts artificial natural curing method. After concrete pouring 12h, cover with sacks or straw bags and water conservation. When there is no admixture in concrete, the curing time shall not be less than 7d, and when there is admixture in concrete, the curing time shall not be less than 14d.
3.2. 12 concrete removal: the side formwork can be removed only after the concrete strength ensures that its surface and corners are not damaged by formwork removal, and the bottom formwork can be removed only after the concrete strength reaches 100%.
Through strict construction, the anti-floating, damage and horizontal displacement of the core mould have been effectively controlled.
4. Conclusion
With the diversification of modern residential buildings and public buildings, traditional structural forms and construction methods are required to be constantly innovated and improved. Cast-in-place reinforced concrete hollow floor is a new structural technology developed in China in recent years. It is suitable for large-space, long-span column-net residential buildings and public buildings, and has the advantages of light weight, large floor stiffness, reduced earthquake action, and increased sound and heat insulation, which has been welcomed by owners. The application of cast-in-place reinforced concrete hollow floor is more and more extensive, and the demand for high-quality and low-cost core formwork is increasing. Many domestic scientific research units and manufacturers are developing core mold products with different materials and components, different shapes and characteristics. In the fierce market competition, high-quality and low-cost core molds will play a very important role in promoting the rapid development of cast-in-place reinforced concrete hollow floor structure technology.