Read the text. Find the key sentences in all passages of the text. Render the text in Russian

Text 5 C

Reinforced Concrete

Reinforced concrete is a combination of two of the strongest structural materials, concrete and steel.

This term is applied to a construction in which steel bars or heavy steel mesh are properly embedded in concrete. The steel is put in position are concrete is poured around and over it, then tamped in place so that the steel is completely embedded. When the concrete hardens and sets, the resulting material gains great strength. This new structural concrete came into practical application at the turn of the 19^th century. The first results of the tests of the reinforced concrete beams were published in 1887. Since that time the development of reinforced concrete work has made great progress. And the reasons of this progress are quite evident. Concrete is poor elastic and tensional properties, but it is rigid, strong in compression, durable under and above ground and in the presence or absence of air and water, it increases its strength with age, it is fireproof.

Steel has great tensional, compressive and elastic properties, but it is not durable being exposed to moisture, it loses its strength with age or being subjected to high temperature. So, what is the effect to the addition of steel reinforcement to concrete?

Steel does not undergo shrinkage or drying but concrete does therefore the steel acts as a restraining medium in a reinforced concrete member. Shrinkage causes tensile stresses in the concrete, which are balanced by compressive stresses in the steel. For getting the best type of reinforced concrete the following consideration should be kept in mind.

1. For general use the most suitable proportions of cement and other aggregate are: 1 part cement, 2 parts sand and 4 parts of gravel.

2. Only fresh water free from organic matter should be used for reinforced work. Sea water is not allowed.

3. Homogeneity of the concrete is a very important requirement.

Steel constructions with reinforced concrete have become the most important building materials invented in centuries and they have given modern architecture its peculiar features.

Read the text and speak different features of aluminum. Give your reason of its usage in construction

Text 5 D

Aluminum in Structures

Aluminum is not a new material. Probably the first example of large-scale structural use of aluminum was in 1933 when the floor steelwork of a large road bridge in Pittsburg, Pennsylvania, was replaced with aluminum and the resulting saving in dead weight – about 1ton/ft run – enable the bridge to carry with greater safety the increased loads of modern traffic. Apart from the construction of aircraft, aluminum has thus a structural history of about only half a century. Extensive use of aluminum in buildings such as aircraft hangers did not occur until about 30 years ago.

In many ways aluminum has been slow in making progress, mainly because of its cost; it is produced by electrolytic means which requires cheap hydro-electric power. About 10 units of electricity are required to make 1 lb. New reduction plants of large capacity have been coming into service in many parts of the world and these provide increased production with improved efficiency. The use of aluminum in structures may well expand in corresponding manner as simultaneous advances are being made with the development of improved aluminum materials and products.

The principal virtues of aluminum are lightness combined with strength and freedom from corrosion. The extent to which the latter its properties are developed depends on the alloy concerned.

The advantage of lightness – one-third the density of mild steel with nearly the same strength – is particularly of value where weight using is of importance – in lift bridges, long span roofs, dome roofs, and in a wide range of moving and portable structures.

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