Construction formwork: technological characteristics and main uses

Building formwork is a building material made from bamboo as the main structural and filling material, formed under high pressure! Bamboo plywood is made by bonding equally thick bamboo strips with grooves as its constituent units, prepared by flattening and planing. "High-temperature softening and flattening of bamboo" is a characteristic process of this product.
The process characteristics of building formwork are:
1. Preparation of equally thick bamboo strips with grooves. Large-diameter moso bamboo is cut into bamboo sections, the outer nodes are milled off, and then longitudinally split into
2-4 pieces, then the inner nodes are milled off for steaming and softening. Then, it is heated and pressed on a single-layer top-pressing machine to unfold the arc-shaped bamboo blocks into a plane. Finally, it is processed into equally thick bamboo strips without bamboo green or yellow by double-sided pressing and planing.
2. Shaped drying. In order to prevent the flat bamboo strips from curling and deforming due to the transverse elastic recovery force during the drying process, it is necessary to use pressure drying technology and equipment to heat the wet bamboo strips under pressure, and when the pressure is released, the moisture and free shrinkage are removed.
3. Bamboo gluing. A four-roller gluing machine is used to roller-coat the bamboo strips with water-soluble phenolic resin glue, with a coating amount of 300-350 g/㎡ (double-sided). 1%-3% flour, bean powder, etc., can be added to the adhesive as a filler. The filler can make it easy for the bamboo strips to form a film on the surface after coating, prevent the glue from flowing during hot pressing, and improve the brittleness of the glue layer after solidification.
4. Assembling. Manual assembling is adopted, strictly following the principles of symmetry, odd-numbered layers, and mutually perpendicular textures of adjacent layers. It is required that the face plate uses good-quality bamboo strips, and the back plate uses inferior bamboo strips. The bamboo green surface of the face and back plates faces outward, and the bamboo yellow surface faces inward; when assembling the core plate, the orientation of adjacent bamboo strips should be arranged alternately according to the bamboo green surface and the bamboo yellow surface.
5. Pre-pressing and hot pressing. Pre-pressing is to prevent displacement during loading into the hot press, causing defects such as overlapping cores and gaps. Before hot pressing after assembling, the slab should be pre-pressed at room temperature to bond it into a whole material. Hot pressing uses a hot-melt adhesive process, with a hot-pressing temperature of about 140°C and a unit pressure of 2.5-3.0 MPa. The hot-pressing time is calculated according to the thickness of the finished plate, generally 1.1 min/mm. In order to prevent the occurrence of "bubble" phenomenon, three-stage pressure reduction is usually adopted in the later stage of hot pressing. The first stage is from the working pressure to the "equilibrium pressure", the second stage is from the "equilibrium pressure" to zero, and the third stage is from zero to the opening of the hot press plate.
6. Lengthening and surface treatment of the plate. Bamboo plywood is mainly used as a car body bottom plate, so the length of the plate must be consistent with the length of the car body, and the pressed plate is shorter, so it needs to be lengthened. The lengthening and surface treatment of the plate include milling the end bevel, bevel coating and lap joint, hot-pressing lengthening, longitudinal trimming, plate surface coating and covering with wire mesh, and hot-pressing again to solidify the plate surface glue layer and press out the mesh marks.
The main uses of building formwork are:
Building formwork grouting, car body panels and bottom plates, large-scale mechanical outer packaging plates, and various places where plates are needed! Due to the high hardness, bending resistance, and compressive strength of bamboo plywood, it has replaced steel formwork in many application areas! Because bamboo is easily cultivated and fast-growing trees, it can be harvested in three to five years, and it can replace wood. Therefore, the national forestry department's policy supports the vigorous development of engineered wood with bamboo as the main processing material, and has replaced the use of wood-based panels in many places!