A saw table and nail able material, wood is one of the first materials used for the production of formwork. Due to its texture and its assembly possibilities, wood formwork has many advantages for exposed structured concrete and for structures of complex and non-repetitive shapes. The boards used for the Modular Formwork must be thick enough to avoid warping (27 to 40 mm), made from wood species free of tannin, dry, and stabilized. For certain applications, sanded, planed, or treated wood is used to highlight, for example, the grain. The wooden formwork allows the realization of visible concrete of quality, presenting varied textures. The characteristics of the wood change during reuse (lower porosity, surface wear); these modifications can have an influence on the color and appearance of the facing. The number of reuse of wooden formwork is therefore limited. For large and flat surfaces, the formwork can be made from plywood panels. But it can also be used for small elements of complex shape, because of its ease of cutting.
Metal formwork
Metal formwork has developed a lot, especially in the building industry. They make it possible to rationalize the use of concrete and help improve site productivity. Their possibilities of reuse are appreciable for elements of a repetitive nature - vertical walls, floors, and posts. The use of stiffeners allows the realization of elements of large surfaces. Formwork made of synthetic materials
Synthetic materials are mainly used to make the skin of the Wall Formwork. They provide a good quality of facing and are easily removed from the mold. This type of formwork is useful for obtaining various reliefs, using thermoformed PVC or polyethylene matrices, or sculpted matrices in expanded polystyrene. Note: plastic is also used for the production of modular formwork of small dimensions (0.5 to 1m2) that can be handled by hand.
Climbing forms
For tall and repetitive constructions, it is interesting to be able to hoist the formwork, not with the aid of a crane, but with jacks fixed the formwork itself and resting on the already concrete and hardened part. It is a climbing formwork which therefore allows concreting by successive lifting. The use of climbing forms is very common for bridge piers or tanks. Most of the time, they are made to measure according to the geometry of the structure.
Lost formwork
Lost formwork is widely used for making Deck System for Slab. They have advantages: speed of execution, simplicity of materials, integration of reinforcements, simplified handling; these are the advantages of these solutions.
The pre-slabs
The most common lost formwork is reinforced or prestressed concrete pre-slab.A pre-slab is a plate 5 to 7 cm thick, with a smooth appearance on the underside and rough on the upper side, to ensure good adhesion of the 2nd phase concrete on this pre-slab. The realization of floors with pre-slabs requires less material than for the shuttering method. The slabs are supported at their ends on wooden rails supported by a line of trees. Intermediate props are needed to limit bending during concreting.
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