1. The most commonly used materials are wood, stone, brick, concrete, steel, glass, plastics, etc. They all differ in hardness, durability, strength, weight, fire- and decay-resistance and, naturally, cost.
Wood is the most ancient structural material. In comparison with steel wood is lighter, cheaper, easier to work with and its mechanical properties are good. On the other hand, wood has certain disadvantages. First, it burns and is therefore unsuitable for fire-proof buildings. Second, it decays.
Stone belongs to one of the oldest building materials used by man. Stone is characteristic of many properties. They are mechanical strength, compactness, porosity, sound and heat insulation, and fire-resistance. Stone is widely used for foundations, walls and steps of buildings, for the supports of piers, and bridges, and for finishing and decorating all sorts of structures.
Bricks were known many thousand years ago. Bricks are hard and easily fastened together with the help of mortar. A brick building is strong, durable and weather resistant.
Concrete is referred to as one of the most important materials. Mass concrete was employed by the Egyptians and the Romans but the use of steel reinforcement did not begin until the nineteenth century. Concrete is a mixture of cement, sand and crushed stone, made into a paste with water. It forms a hard, durable mass and is used largely for the foundations and walls of houses and for structures under water.
Steel has come into general use with the development of industry. Its manufacture requires special equipment and skilled labour.
Glass and plastics are also widely used nowadays in the construction of different kinds of buildings. The raw materials employed in the manufacture of glass are limestone, sand, soda ash, sodium sulfate, cullet (broken glass), and a small amount of aluminia. Glass is unaffected by gasses and most acids.
Plastics is a name for various organic derivatives of resin, cellulose, and protein.
2. All building materials are divided into three main groups:
1). Primary (main) building materials such as rocks and artificial stones, timber and metals are used for bearing structures.
2). Secondary (auxiliary) materials are used for the interior parts of the buildings, for the interior finish of structures.
3). Cementing or binding materials such as lime, gypsum and cement are the three materials most widely used for the purpose of binding together masonry units, such as stone, brick and as constituents of wall plaster.
Building materials can be further categorized into two sources, natural and synthetic. Natural building materials are unprocessed or minimally processed by industry, such as timber, sand, lime or stone. Whereas synthetic materials are made in industrial settings after some human manipulations, such as plastics and petroleum based paints. Cement, clay products and concrete are also examples of artificial buildings materials.
Дата добавления: 2015-09-12; просмотров: 20 | Поможем написать вашу работу | Нарушение авторских прав |