Relatively solid and durable fibrous material, the main part of trunks, branches, and roots of trees and bushes. It consists of countless tubular cells with membranes mainly of cellulose, firmly cemented with calcium and magnesium pectates into an almost homogeneous mass.
In its natural form it is used as a building material and fuel, and in shredded and chemically cultivated form it is used as a raw material for the production of paper, fiberboards, and artificial fiber.
Wood was one of the main factors for the development of civilization and even today it remains one of the most important types of raw materials for humans, without which many industries could not exist.
Application in construction. Wood is used in construction in such forms as lumber of rectangular section (timbers, boards), veneer, plywood, railway sleepers, posts, piles, pillars, shingles, and fiberboards.
The most used lumber is in shape of rectangular cross-section. They are made by sawing logs, then being trimmed to a standard width and length, sorted by quality, dried and delivered to consumers in a raw, cultivated, or molded form.
Plywood is made by gluing an odd number of thin layers of wood (veneer) so that the fibers of the adjacent layers are mutually perpendicular. Plywood panels differ from conventional sawn timber in the way that (along with the absence of restrictions on width) their hardness is more uniform in different directions, they better resist splitting, and their dimensions change less in conditions of variable humidity.
Protection of wood from destruction. To ensure durability, the wooden structure must be protected from rotting and destruction by wood-boring insects. Antiseptic protection of structures against rotting is applied in specialized workshops of woodworking companies or directly at the construction site.
Industrial antiseptic has better quality, as it can be applied under pressure in a strict technological mode. Only greasing or impregnation of products is done at the construction site. Coal creosote oil, solutions of pentachlorophenol in liquid hydrocarbons, aqueous solutions of zinc fluorides and chlorides, arsenites, arsenates, etc. are used as antiseptics.
Chemicals – insecticides, are used to protect the wood from destruction by insects (tree borers). Aqueous solutions of insecticides are applied to the surface with brushes or sprayers. Due to the fact that dry wood is highly flammable, it is necessary to follow the rules that provide fire protection for wooden structures.
The protection from fire of such structures is achieved by coating the wood with fire retardant materials: plaster, coating, painting with special liquid formulations. Wood is also impregnated with chemicals that increase its fire resistance, for example, phosphoric acid, ammonium, or magnesium phosphates. The wood treated in this way becomes charred when heated but burning stops as soon as the heating is reduced.