What is a plywood for formwork?
Plywood formwork is a temporary support structure, according to the design requirements of production, so that the concrete structure, components according to the specified position, geometric size shape, keep its correct position, and bear the plywood formwork weight and the external load on it. The purpose of formwork engineering is to ensure the quality of concrete engineering and construction safety, speed up the construction progress and reduce the project cost.
Plywood formwork for concrete sizes:
China’s commonly used formwork plywood sizes: 830mm X 915mm, 1220mm X 2440mm, thickness: 11 ~ 18mm.
Plywood formwork material
Bamboo veneer plywood
With bamboo material as the main structure and filling materials, through high pressure billet building materials. It is suitable for horizontal formwork, shear wall, bridge and viaduct. The surface of the bamboo plywood is smooth and flat, with good effect and good water resistance, not easy to be affected by moisture.
By poplar wood rotary cut into veneer or by wood planer cut into thin wood, and then glued with adhesive laminated laminated material. Usually with odd layers of veneer and adjacent poplar veneer plywood fiber direction perpendicular to each other. Poplar wood is light in weight, clear in texture and low in cost.
Pine plywood is a kind of building materials commonly used in south square construction projects, mostly used in housing construction. Pine plywood costs high, but high turnover times, not easy to expand deformation.
By eucalyptus rotary cut into veneer or by wood planer cut into thin wood, glued. Buildings, Bridges, tunnels, nuclear power projects and other large infrastructure, as well as concrete art landscape, steel and aluminum frame formwork. Small expansion coefficient, moisture resistance, high temperature resistance, smooth and beautiful construction surface.
Classification of plywood formwork
Classification by material
According to the different materials used, formwork are divided into wood templates, steel and wood templates, steel templates, steel bamboo formwork, plywood formwork, plastic templates, FRP templates, aluminum alloy templates, etc.
Classification by structure type
All kinds of cast-in-place reinforced concrete structural members have their own characteristics due to their different shapes, sizes and structures, as well as different formwork construction and assembly methods.
According to the type of structure template is divided into: foundation template, column template, beam template, floor template, stair template, wall template, shell template, chimney template and so on.
Classification by construction method
Site assembly and disassembly type template: site assembly and disassembly type template with shaped template and tool support; Fixed formwork: all kinds of tire mold (soil tire mold, brick tire mold, concrete tire mold) is a fixed template; Mobile formwork: such as chimney, water tower, wall column concrete pouring when the use of sliding up formwork, lifting formwork and shell pouring concrete using horizontal mobile formwork.
Plywood formwork selection
Look at the texture
Texture is the standard to judge whether a formwork is good or bad. Regular texture is well-structured and beautiful, indicating that the core plate of the building formwork is made of first-class raw materials, with standard size and uniform thickness. The finished product to make uniform thickness, not easy to deformation and fracture.
Look at the density and weigh it
Generally speaking, the formwork of the same specification, if the weight is heavier, the density of the formwork is relatively high, the pressure in the production process is relatively large, the choice of material hardness is high, the bonding strength of the formwork is relatively high, the formwork strength is good.
Preservation of plywood formwork
After the demolition of the building formwork, the waist of the formwork should be completely cleaned with the scraper to facilitate the turnover of the formwork; If the formwork needs to be stored for a long time, it should be coated with oil agent on its surface, stacked neatly and covered with a rain cloth; In the process of transportation and storage to avoid sun exposure and guide formwork deformation and aging; Finally, on the construction site, the formwork should be stored in a flat, dry place, must avoid the temperature and humidity are very extreme places.
Erection of building formwork
*The interior of the ply formwork should be cleaned up. Debris left in the building formwork will cause defects such as concrete slag inclusion. Clearance openings shall be reserved for removal of building forms.
*When supporting plywood used for formwork, the requirements for 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. Deviation in accordance with acceptance specifications.
*Building formwork should be coated with isolation agent. When brushing, choose not to affect the structure and interfere with the decoration construction of oil isolation agent. At the same time, because of the isolation agent pollution of steel and concrete joints may be on the concrete: soil structure mechanical performance caused by obvious adverse effects, so should avoid brushing pollution of steel.
*For multi-storey cast-in-place structure, superstructure formwork and support must be supported on the lower floor slab. At this time should pay attention to three points: first, the lower floor should have enough bearing capacity, if necessary, should be added support; Second, the columns of the upper and lower brackets should be basically aligned; Three, the support column should be laid under the backing plate. During construction, the requirement of laying gasket is applicable not only to the floors but also to the building formwork columns installed on the ground.
*Building plywood formwork joints should not leak slurry: building formwork leakage slurry, will cause the appearance of concrete honeycomb hemp, directly affect the quality of concrete. Therefore, no matter what kind of materials are used to make building formwork, the joints should be strict and no slurry leakage. When use wood building formwork, because the wood will expand and shrink, so the joint of the wood building formwork installation is not straight too tight, after the installation should be watered and wet, so that the wood joint is closed. When watering, it is ok to wet, building formwork should not be standing water.