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Plastics

Air, water, sand, salt, coal, petroleum are familiar elements in the everyday life, but these form the basic sources of the world's fastest growing (расти) industry -plastics.

From a purely engineering viewpoint the following characteristics of plastics explain their increasing acceptance by industries and consumers alike. These characteristics are usually shared by all plastics, but there are variations between individual materials: lightweight (sometimes high strength to weight ratio); corrosion resistance; electrical and thermal insulation; ease of fabrication; transparency in some materials; ease of the increasingly successful application of plastics which take advantage of these characteristics have meant that plastics materials are now manufacturing materials in their own rights and not substitutes. The high strength to weight ratio of some plastics offers big field in the coming age of space travels and rockets.

The same benefits of light weight with good strength and absence of corrosion offer tremendous potential as alternatives to traditional building materials. New shapes in building are absorbing the attention of the architects. Plastics offer many of properties for these designs and their application in exotic structures is an example.

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1.The basic sources of plastic are …

2.The characteristics of plastics, which increase its use in industry and by consumers, are …

3. It will be used in this age of space travels and rockets because of …

4.Plastics offer new shapes in building and application in exotic structures because of combination of …

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From the history of concrete

Mass or plain concrete dates from very early days. It was employed in ancient times by the Egyptians, Romans and Greeks in the construction of aqueducts and bridges, in the construction of roads and town walls. Romans used it even in under-water structures some of which have survived till our time. They also employed concrete as a filling between the brick and stone ribs of the vaults and arches. A large part of the Great Chinese Wall (the 3rd century before our era) was also built of concrete.

The concrete remains of the foundations of buildings built several thousands years ago have been found in Mexico. As cement was not known in those times, concrete was made of clay and later of gypsum and lime. The knowledge of the concrete use seems to have been lost during the Middle Ages, and it was not until the eighteenth century that its value was rediscovered. Nowadays concrete is made in up-to-date machinery with very careful regulation of the proportion of the mix.

The idea of strengthening concrete by a network of small iron rods was developed in the 19th century, and ferro-concrete was introduced into engineering practice. Since that time the development of reinforced concrete work has made great progress. And the reasons of this progress were evident. Between 1880-1890 several reinforced concrete buildings were erected in the United States, and since 1896 the increase in the amount of construction with this material has been remarkable.

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1. Mass or plain concrete was employed in ancient times in …

2. Romans also used concrete as a filling…

3. As cement was not known in ancient times concrete was made of …

4. The knowledge of the concrete use … in the Middle Ages.

5. Nowadays concrete is made …

6. The idea of strengthening concrete by … was developed in the 19th century.

7. Between 1880-1890 … were built in the United States.

Read again the additional texts and give main ideas using the following expressions:

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At the beginning of the text the author stresses (underlines, points out) that …

Then the author describes smth (suggests, states that) …

After that the author passes on to (description of, statement of, analysis of …}

At the end of the text the author comes to the conclusion (pays attention to the fact) that…