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Рубрика:
1. John visited me in the hospital yesterday.
2. A yellow bird fell on the roof of his Pontiac.
3. I was taken by surprise.
4. Despite the stormy weather he was able to swim to the shore.
5. He couldn't reach the hammer which lay on the shelf.
6. Our bus was broken.
7. I have been cheated by the best friend.
8. A girl from Barbados wrote a letter to BBC.
9. The clock stopped an hour ago.
10. You have to stop near the traffic lights.
# Put in -a, -an or -the where it is necessary.
There were only ... two people in ... hall when I went in, ... man with ... long beard and ... child. ... child
was sitting on ... chair by ... window, playing with ... small kitten, while ... man with ... beard was reading ...
newspaper. Suddenly he put ... newspaper on ... table which stood by, and said, “... president is shot dead in ...
Alabama". ... child burst into ... tears. "Don't cry", said ... man, "you wanted to be ... president, and you'll be ...
next one."
Lesson 3
High - Strength Concrete
Pre-reading Discussion
1. What types of concrete do you know?
2. What are the main characteristics of high-performance concrete?
3. Do you agree that to construct a building designers must take many things into consideration?
4. It’s important to take into account the climate of the region while constructing the building, isn't it?
5. What has been the greatest step forward in concrete technology in recent years?
High – Strength Concrete
Today, new types of concrete are available that mark a considerable advance on normal concrete in terms
of their strength and ductile behavior. It has been possible, for example, to increase the compressive strength.
In addition to purely technological developments, there has also been a great increase in the use of cementicious
elements in composite forms of construction. Of special interest in this respect is the creation of fiber-
reinforced and textile-reinforced concrete.
Fibre-reinforced concrete, for example, has helped to improve the ductile properties of the material. Indeed, in
certain situations, such as load-bearing walls in housing construction, fibres can replace conventional steel rod rein-
forcement. Glass-fibre-reinforced concrete is mostly used for slender constructional elements, e.g. roof coverings,
shell structures, and facade slabs.
Textile-reinforced concrete is a logical development of glass-fibre-reinforced concrete, since it allows the
direction of the load-bearing reinforcement to be controlled, in contrast to the random arrangement of reinforc-
ing fibres. With textile-reinforced concrete, it is possible to create extremely thin and lightweight elements,
which have a great potential in architectural design. The development of self-compacting concrete marks a
quantum leap in processing techniques. The properties of this type of concrete afford virtually unlimited scope
for design in terms of unit geometry and surface treatment. The materials used in high-performance concrete
usually mean that it is considerably more expensive than normal concrete. Depending on the application, an in-
crease in costs ranging from 50 to as much as 200 per cent or more may be expected. These figures are related
to a cubic meter of concrete, however, so that the additional costs may be offset in part by reductions in the
cross-sectional dimensions of elements and the resulting increase in rentable space.
The fibres used may be of plastic, glass or steel. Plastic fibres are mostly used to reduce cracking as a result
of early shrinkage in concrete, but they also serve to increase fire resistance; for example, in high-strength con-
crete. Polypropylene fibres, which are most commonly used for this purpose, vaporize at high temperatures, but
the precise mechanism involved has not been finally established. Glass fibres are used to reduce cracking in set-
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