The most important and widely used building materials

The designer must be able to select and adapt such materials of construction that will give the most effective result by the most economical means. In this choice of materials for any work of construction, the civil engineer must consider many factors. These factors include availability, cost, physical properties of materials and others.

Timber, steel and concrete all vary, sometimes over considerable ranges in the properties desired by the engineer. Even steel varies considerably in its microstructure. Concrete is even less uniform than many other materials.

Lime, gypsum and cement are the three materials most widely used in building construction for the purpose of binding together masonry units, such as stone, brick and as constituents of wall plaster. Cement is furthermore the most important component of concrete.

Another important class of cement is high alumina cement. High alumina cement is a material containing alumina. It has an extremely high rate of strength increase which is owing to the violence of the chemical reaction, accompanied by a considerable evolution of heat. It is very resistant to chemical attack.

Portland cement like other materials can be modified to suit a particular application. The scope for such purpose-made cement has led to the development of an increasing variety such as high alumina cement, blast-furnace slag, etc. Portland blast-furnace cement has greater resistance to some forms of chemicals.

The most important building materials are steel and concrete. Concrete may be considered an artificial conglomerate of crushed stone, gravel or similar material with mortar. A mixture of sand, cement and water which has the capacity of hardening into rockline mass is called mortar. The fundamental object in proportioning concrete or mortar mixes is the production of a durable material of requisite strength, watertightness and other essential properties at minimum cost. The most accurate method of measuring proportions is to weigh the required quantities of each material. It is widely used in large building construction, but in small building construction the less accurate method of measuring proportions by volumes is frequently used. Workability and strength tests are chief control tests made on concrete. To be able to undergo high compressive loads is a specific characteristic of this material.

Ex.2 Answer the questions.

1. What must the designer be able to do?

2. Who must consider many facts in choice of materials?

3. What factors must consider civil engineer?

4. What materials does civil engineer have for its properties?

5. How may steel be varies?

6. What materials are the most widely used in building construction?

7. For what purpose may lime cement and gypsum be used?

8. What is the most important component of concrete?

9. What is the important class of cement?

10. What is the high alumina cement?

11. What influence may alumina concrete resist?

12. What cement can be modified to suit a particular application?

13. What varieties of concrete have appeared?

14. What may Portland cement resist?

15. How may important building materials be considered?

16. What may the concrete be considered?

17. What is mortar?

18. What is the fundamental object in proportioning concrete?

19. What must you give careful attention to attain this object?

20. What is the method of measuring proportions?

21. What measuring method is frequently used in small building construction?

22. Why is this method inaccuracy?

23. What are the control tests for concrete?

24. What is the specific characteristic of concrete?

TEXT 3

Ex.1 Read the text and translate it into Russian.

THE CHOICE OF MATERIAL

Which material can be used to the best advantage for a particular part of the building, depends on the kind of load to which it is subjected and on the shape of the part. The development of the metallurgical and machine-building industry made possible mass production of prefabricated large-size concrete and reinforced-concrete structural elements is a well-known factor to influence the choice of materials.

Reinforced concrete is a building material in which the joint functions of concrete and steel are advantageously utilized. Being brittle, concrete cannot withstand tensile stresses, and it cannot therefore be used in structures subjected to tensile stressed under load. But if steel is introduced into concrete it changes the property of monolith.

There are two kinds of reinforced concrete: with ordinary reinforcement and concrete with prestressed reinforcement. To reinforce ordinary concrete structures is to introduce steel in stretched zones of concrete elements. Reinforced-concrete structures and elements are widely used both for residential houses and industrial buildings.

In many cases bricks are very satisfactory for use in the construction. Bricks generally present a pleasing appearance and can be obtained with various qualities, colours, and textures. Being of a high volume weight and high thermal conductivity, ordinary brick is not always satisfactory in building practice. There are other kinds of bricks which are more effective, they are light-weight building bricks, hollow or porous bricks. Light-weight building bricks differ from ordinary clay bricks in a lower volume weight and lower thermal conductivity, and are therefore more economical than ordinary bricks.

One of the most significant facts about both industry and building has been research on synthetics and plastics. Plastics have appeared comparatively recently but, owing to their inherent valuable and diverse properties, have found a wide application in many industrial fields (machine-building, aviation, textile industry, etc.).

In respect to physical and mechanical properties at normal temperature of 20˚C all plastic are divided into rigid, semi-rigid, soft and plastic. In respect to the number of constituents plastics may be classified as simple and complex.

Plastics consisting of one polymer are referred to as simple. Thus, organic glass (plexiglass) consists of one synthetic resin. But in the building field we usually deal with complex plastics, e.g. plastics consisting of a polymer and other components.