Wood as building material
Wood is an organic, hygroscopic and anisotropic material. Its thermal, acoustic, electrical, mechanical, aesthetic, working, etc. properties are very suitable to use it is possible to build a comfortable house using only wooden products.
With other materials, it is almost impossible. But wood has some disadvantages too. Following is some very short information about this subject and the benefits of wood.
Thermal properties:
As we know, many, materials change in size and volume as the temperature changes. They expand with increasing of the temperature. This means linear and volumetric expansion. The expansion. The expansion causes decrease in the strength of materials. Steel, which is inorganic and non-combustible and therefore has an advantage against fire, but when used in buildings, it expands and collapses as a result of increase in heat.
Wood does not practically expand against heat. On the contrary, by the effect of heat, it dries out and gains strength. The only time wood expands a little is when the humidity level is below 0%, and this is only scientifically significant. In practice, the humidity level of wood does not drop under 5% even in the driest climate.
The coefficient of thermal conductivity of the wood is very low. Aluminum transmits heat 7000 times, steal 1650 times, marble 90 times and glass 23 times faster than wood. For this reason, wood is used for making matches, handles of hardware equipment, ceilings and wall coverings.
Specific heat of wood is high. That means high amount of energy is needed to increase and decrease the temperature of one-kilogram of wood. Wood requires almost twice amount of heat energy than stones and concrete; similarly, three times of energy is needed for heating or cooling steel.
Acoustic properties:
Sound isolation is based on the mass of the surface. Wood, as a light material, is not very perfect for sound isolation; but it is ideal for sound absorption. Wood prevents echo and noise by absorbing sound. For this reason it is extensively used in concert halls.
Sound velocity is faster in woods than gases and liquids, and it is close to that of metals. Sound energy loss as a result of friction is also significantly low in woods due to its lightness and structure. Because of such properties, wood is extensively used in musical instruments.
Electrical properties:
Resistance to electrical current of a completely dry wood is equal to that of fhenol formaldehit. An oven dried wood is a very good electrical insulator. To some extent air dried wood is the same. Unfortunately electrical resistance of wood is lowered by increasing the moisture content. The resistance of wood saturated with water. Static electricity that is dangerous for human health is not observed in wood unlike metal, plastic and other materials. For this reason wood is preferred as a healthy material.
Mechanical properties:
Although wood is a light material, its strength is quite high. For instance, while the tensile strength of wood with 0,6/cm3 specific gravity is 100 N/mm2, the tensile strength of steel with 7,89/cm3 specific gravity is 500 N/mm2. Dividing tensile strength by specific gravity gives the breaking length and quality of material. This figure means the breaking length of the material, when hung as a result of its own weight. While the breaking length of steel is used for construction is 5.4 km, chrome mobile steel is 6.8 km, hardened bow steel is 17.5 km, breaking length of spruce wood is 19.8 km, and laminated wood made of beech is 28.3 km. For this kind of properties, wood and laminated wood is used in wide-gap constructions like health centers and sport halls.
Aesthetic properties:
Wood is a decorative material when considered as an aesthetic material. Each tree has its own color, design and smell the design of a tree does change according to the way it is sliced. It is possible to find different wooden materials according to color and design preference. It can be painted to darker colors of varnished, and can be given bright or mat touches.
Oxidation properties:
Although wood has oxidation characteristics in some way, it is not the kind of oxidation seen in metals. Metals get rust, wood doesn’t. For such characteristics, use of wood is preferred to avoid rust when necessary.
Working properties:
It is easy to repair and maintain wood. While old woods can be renewed by special touches other materials are highly difficult and costly to maintain and to repair. Therefore they are usually disposed of.
There are disadvantages of wood, though, but there are ways to eliminate them.
Shrinkage and swelling of wood:
Wood is a hygroscopic material. This means that it will adsorb surrounding condensable vapors and loses moisture to air below the fiber saturation point.
Deterioration of wood:
The agents causing the deterioration and destruction of wood fall into two categories: Biotic (biological) and abiotic (non-biological).
Biotic agents include decay and mold fungi, bacteria and insects.
Abiotic agents include sun, wind, water, certain chemicals and fire.
Biotic deterioration of wood:
Woods are organic goods. Like any organic good, wood is a nutritional product for some plants and animals. Humans can not digest cellulose and the other fiber ingredients of wood, but some fungi and insects can digest it, and use it as a nutritional product. Insects drill holes and drive lines into wood. Even more dangerously, fungi cause the wood to decay partially and even completely.
Biological deterioration of wood due to attack by decay fungi, wood boring insects and marine borers during its processing and in service has technical and economical importance.
Fungi:
It is necessary to give some short information about fungi agents to take measures against the wood deterioration.
Physiological requirements of wood destroying and wood inhabiting fungi: A favorable temperature.
The temperature must be 25-30°C for optimum growth of most wood rotting fungi. But some of them can tolerate temperature between 0-45°C.
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