Plywood formwork purchase
Look at the texture
The texture is the standard for judging the quality of the plywood for formwork. The regular texture is clearly layered and beautiful, indicating that the core board of the plywood for formwork is made of first-class raw materials, the size is standard, and the thickness is uniform. The finished plywood has uniform thickness and is not easy to deform or break. So don't use those plywood formwork for concrete with messy textures!
Look at the density and weight
Generally speaking, if the formwork of the same specification the weight is heavier, the density of the formwork will be higher, the pressure during the production process will be greater, the hardness of the selected material will be high, the bonding strength of the formwork will be relatively high, and the strength of the formwork will be relatively high.
To boil with boiling water, it is necessary to compare the formwork of different manufacturers with the same technology under the same conditions. Generally speaking, the ply formwork of well-known brands can be boiled for more than 8 hours. Some good brands of phenolic glue can be boiled for more than 15 hours, and then see if there is any splitting or degumming.
It is inevitable that the middle and low-end plywood for formwork have cracks, but too large is not good. Some cracks are generated between the grain of the wood, this kind of cracks will not extend, and can be used with confidence. Some cracks penetrate the texture, so you can't buy them, because such cracks will extend and have a great negative impact.
Plywood used for formwork installation
1. The interior of the building formwork should be cleaned up. The debris left in the building formwork will cause defects such as slag inclusion in the concrete. In order to clear the building formwork, a cleaning port should be reserved.
2. When supporting the plywood building formwork, the requirements for the embedded parts and reserved holes should be to fix the embedded parts, reserved holes and reserved holes on the building formwork at the same time, without leaving, the size meets the requirements, and the installation is firm. The deviation meets the requirements of the acceptance specification.
3. The plywood for concrete formwork should be painted with release agent. When painting, choose an oily release agent that does not affect the structure and hinder the construction of the decoration project. At the same time, since the release agent polluting the steel bar and the concrete junction may have a significant adverse effect on the mechanical performance of the concrete structure, it is necessary to avoid contaminating the steel bar during painting.
4. For multi-layer cast-in-place structures, the upper building formwork and brackets must be supported on the lower floor slab. At this time, three points should be paid attention to: First, the lower floor should have sufficient bearing capacity, if necessary brackets should be added; second, the columns of the upper and lower brackets should be basically aligned; third, the slabs should be laid under the columns of the brackets. In construction, the requirements for laying pads are not only applicable to floors, but also to the building formwork columns installed on the ground.
5. The joints of the building formwork should not leak: the leaking of the building formwork will cause the honeycomb and pockmarked surface of the concrete appearance, which will directly affect the quality of the concrete. Therefore, no matter what material is used to make the building formwork, its joints should be tight and not leaking. When using wooden building formwork, because the wood will expand and shrink when it absorbs water, the joints of the wooden building formwork should not be too tight during installation. After installation, it should be watered and moistened to close the joints of the planks. It is enough to be moist when watering, and there should be no accumulation of water in the building formwork.
Correct use of plywood for concrete formwork
1. It is recommended to use the whole multi-layer board (both wood and bamboo) for the building formwork, and try to use the 15-18mm thick multi-layer building formwork with phenolic cladding. The edge of this kind of building formwork is damaged after repeated use, so it must be cut in time to ensure that the edge of the multiplex plywood is flat.
2. The beam and column building formwork should be medium-sized combined building formwork. Because of the large changes in the cross section of beams and columns, it is not suitable to cut with multi-layer boards.
3. The wall formwork can be assembled and dismantled as a large formwork with a medium-sized combined building formwork. It can also be made into a large formwork with a whole multi-storey building formwork, or an all-steel large formwork can be used. Generally, the same type of high-rise building groups should be unified as much as possible to ensure a higher turnover rate.
4. Make full use of the old multi-layer boards and short residual wood after multiple cuts to produce various specifications of small and medium-sized wood composite formwork, which are used for various small and medium-sized cast-in-place concrete components, but these wood height of the shaped formwork is uniform in size, the board surface is flat, the weight is light, the rigidity is good, and it is not easy to damage.
5. Make full use of the existing small steel molds. And meet the requirements of clear water concrete. According to the experience of some film plywood companies, the surface layer of the combined small steel mold can be covered with plastic plates or other thin plates, and used on floor slabs, shear walls or other components.
6. The arc-shaped walls are increasing day by day, and the curvature is changeable. After processing the finalized arc-shaped formwork, it will be changed several times after using it, which costs labor and materials. Recently, some projects have widely promoted the application of "curvature-adjustable arc-shaped formwork". The arc formwork with any radius can be adjusted by the regulator, the effect is remarkable, and it is worthy of vigorous promotion and application.
7. The core tube of super high-rise or high-rise buildings should adopt "hydraulic climbing formwork". The climbing formwork process combines the advantages of large formwork and sliding formwork. It can rise layer by layer with the construction of the structure, and the construction speed is faster, saving space and Tower crane hoisting times, safe high-altitude operation, no external scaffolding, construction, especially suitable for the construction of steel structure concrete inner cylinder.
Building formwork preservation
After dismantling the building formwork, use the scraper to completely remove the surface of the formwork to facilitate turnover; if long-term storage is required, the surface of the formwork should be smeared with oil, stacked neatly and covered with rain cloth; avoid daylight during transportation and storage. Deformation and aging of the formwork caused by the sun; finally, on the construction site, the formwork should be stored in a flat and dry place, and must be avoided in a place with extreme temperature and humidity.
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