TEXT 17. Modern building materials. Part I.

Some of the most important building materials are: timber, brick, stone, concrete, metal, plastics and glass. Timberis provided by different kinds of trees. Timbers used for building purposes are divided into two groups called softwoods and

hardwoods. Timber is at present not so much used in building construction,

as in railway engineering, in mining and in the chemical industry where it provides a number of valuable materials. However, timber is still employed as a building material in the form of boards. For the interior of buildings plywood and veneer

serve a number of purposes.

A brickis best described as a "building unit". It may be made of clay by moulding and baking in kilns, of concrete, of mortar or of a

composition of sawdust and other materials. In shape it is a rectangular solid and its weight is from 6 V2 to 9 lb. There exists variety of bricks for different purposes: ordinary, hollow or porous, lightweight, multicolor bricks for decorative purposes,

etc. Bricks are usually laid in place with the help of mortar. The shape and convenient size of brick enables a man to grip it with an easy confidence and, because of this, brick building has been popular for many hundreds of years. The hand of the average man is large enough to take a brick and he is able to handle more than 500 bricks in an eight-hour working day. It is necessary, therefore, for the "would be" bricklayer to practice handling a brick until he can control it with complete mastery and until he is able to place it into any desired position.

The brick may be securely handled by placing the hand over the surface of the upper part of a brick and by placing the thumb centrally down the face of the brick with the first joints of the fingers on the opposite face. It is better to protect the thumb and the fingers with leather pads, which also prevent the skin from rough bricks. Sometimes natural stones such as marble, granite, basalt, limestone

and sandstone are used for the construction of dams and foundations. Marble, granite and sandstone are widely used for decorative purposes as well, especially with the public buildings.

Natural stone is used for foundations and for the construction of dams. The main varieties of building stone are basalt, granite, marble, sandstone and limestone. Metals: Aluminium, principally in the form of various alloys, is highly valued for its durability and especially for its light weight,while brass is frequently used for decorative purposes in facing. Steel finds its use in corrugated sheets for roofing, for girders, frames, etc. Various shapes are employed in construction. Plastics are artificial materials used in construction work *for a vast number of purposes.2 Nowadays plastics, which are artificial materials, can be applied to almost every branch of building, from the laying of foundation to the final coat of paint. Synthetic resins are the main raw material for plastics. Plastics have some good advantages as they are lighter than metals, not subject to corrosion, and they can be easier machined. Besides, they are inflammable, they can take any color and pattern, and they are good electrical insulators. More over, they possess a high resistance to chemical action.

A lot of decorative plastics, now available, have brought about a revolution in interior and exterior design. But plastics are used now not only for decoration. These materials are sufficiently rigid to stand on their own without any support. They can be worked with ordinary builders' tools.

Laminate is a strong material manufactured from many layers of paper or textile impregnated with thermosetting resins. This sandwich is then pressed and subjected to heat. Laminate has been developed for both inside and outside use. It resists severe weather conditions for more than ten years without serious deformation. As a structural material it is recommended for exterior work. Being used for surfacing, laminate gives the tough surface.

Foamed glass is a high-porosity heat insulating material, available in block made of fine-ground glass and a frothing agent. Foamed glass is widely used in prefabricated house building, to ensure heat insulation of exterior wall panels, and in industrial construction. Foamed glass has a high mechanical strength, is distinguished by moisture, vapor and gas impermeability. It is non-inflammable, offers resistance to frost, possesses a high sound adsorption, and it is easily sewn and nailed. Structural foamed glass blocks designed to fill ceilings, and for making interior partitions in buildings and rooms, to ensure heat and sound insulation. For insulation mineral wool or cinder wool is often resorted to.