Unit 5. Construction materials.

Vocabulary

Properties – свойства

Durability – долговечность, износостойкость

Decay-resistance –стойкость к гниению

Advantages and disadvantages – преимущества и недостатки

To evaporate – испаряться

Renewable natural resource – возобновляемые природные ресурсы

Facings – облицовка, отделка

Paving – мощение улиц

Width, breadth - ширина

Length – длина

Height – высота

Weight - вес

Dimensions – размеры

Local custom – местный обычай

Crosswise – крестообразно, в поперечном направлении

Lengthwise – в длину, в продольном направлении

Clay - глина

Materials used for construction purposes possess different properties. They differ in durability, strength, weight, fire-and decay-resistance and cost.

Wood, timber, brick, stone, concrete, metals, and plastics belong to the most popular building materials used nowadays. They all have their advantages and disadvantages that are taken into account when designing a structure.

Wood is naturally growing materials. It is known to be the oldest construction material and is still widely used for different purposes. Wood is popular since it has low weight and is easy to work. But its usage is limited because of its disadvantages: it easily burns and decays. Wood has been a highly used building material since prehistoric times. Being the oldest building material, wood is also known to be the only naturally growing organic material. Is wood strong? Hardly so, because wood always contains some water which decreases its strength. But after the wood is cut, the water content starts to evaporate and as the water content decreases the strength of cut wood and its hardness start to increase. It is a well-known fact that the drier is the cut wood the greater is its strength and hardness.

Trees are known to grow naturally, which makes wood a constantly renewable natural resource. Among other advantages of wood there are its low cost, low weight, and high workability. But, as any other construction material, wood has its disadvantages. The main ones are the following-it is not fire-resistant, it easily burns.

Among other highly used construction materials there are concrete, steel, brick, stone, and plastics. They all differ in their properties and in the methods of usage.

As to stone, it also belongs to the oldest building materials. Among its advantages there are strength, high heat insulation and fire-resistance.

Concrete is known to be one of the most popular building materials. It is produced by mixing cement, gravel, water, and sand in the proper amounts.

Bricks are an ancient building material, having been made and used by the Romans for arches, facings, paving etc. Though they were, at that period, of larger and smaller sizes than those used generally in the present day, they were always made with half-bricks or double bricks— double their width in length — to allow of bond, as will hereinafter be explained. They thus varied in length from 7 to 22 inches.

In more modern times bricks have been used for walling, facing, arches, and paving; and generally their dimensions are now about 9 inches long by 41, inches (or half their length) in breadth, so that two laid crosswise will cover two laid lengthwise. They are made from 2 to 31 inches in height, according to local custom or the requirements of construction. They are of numerous different qualities, kinds, and colours, each from its peculiar nature adapted to a particular purpose or use. It is to be noted that the quality of a brick depends on the clay from which it is made, and on the different manipulation which the clay will.