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Lesson 9.
CONCRETE
Second only to water, concrete is the most consumed material on earth, with three tonnes per year used for every person. Twice as much concrete is used in construction as all other building materials combined. There is little doubt that concrete will remain in use well into the future.
Text 0.
From the History of Concrete.
Mass or plain concrete dates from very early days. It was employed 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. 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 thousand 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.
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 on the 19th century, and ferro-concrete was introduced into engineering practice.
Vocabulary (1)
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бетон летучая зола, зольная пыль, зола-унос бесклинкерный шлаковый цемент, известково-шлаковый цемент крупный заполнитель мелкий заполнитель устанавливается отлит форма желаемая форма железобетон преднапряженный бетон сборные блоки использоваться широко кондиционность главный измельчать пыль, крошка, порошок шлако-портландцемент выдерживание бетона количество прочный, долговременный доки щелочной шлакобетон бетон с добавлением летучей кремноземной пыли шлак натрий калий песчанистый суглинок стандартный цемент оросительная система почва, жесткий пол на грунте |
Text (1)
Concrete
It is difficult to imagine modern structure without concrete. Concrete is the very building material which led to great structural innovations. Concrete is perhaps the most widely spread building material used nowadays. Concrete is an artificial stone, that consists of cement (commonly Portland cement) as well as other cementitious materials such as fly ash and slag cement, aggregate (generally a coarse aggregate such as gravel limestone or granite, plus a fine aggregate such as sand or manufactured sand) and water and chemical admixtures to produce a mixture of the proper consistency.
It has many valuable properties. It sets under water, can be poured into moulds so as to get almost any desirable form, and together with steel in reinforced concrete it has very high strength, and also resists fire. Prestressed concrete is most widely used at present while prefabricated blocks are employed on vast scale for skeleton structures.
The most important quality of concrete is its property to be formed into large and strong monolithic units. The basic materials for making concrete are cement, aggregate and water.
Cement is the most essential material and the most important one for making concrete of high quality. Cement is made of limestone and clay. It is burnt (calcined) at high temperature and ground up into powder. Depending on the kind and composition of the raw materials different types of cement are obtained. Portland cement, blast furnace cement is suitable for putting up marine structures.
Concrete is made by mixing cement, water, sand and gravel in the right amount. As soon as it is thoroughly mixed it is poured into forms that hold it in place until it hardens. The crystals forming in the process of making concrete stick together in a very hard artificial stone. Cement starts hardening one hour after the water has been added and the process of hardening lasts for about 28 days. The process is called concrete curing.
The characteristics of concrete depend upon the quality of the materials used, grading of the aggregates, proportioning and amount of water. The most important requirements for concrete are: it should be hard, strong, durable, fire-resistant and economical.
Concrete can be divided into 2 classes: mass or plain concrete and reinforced concrete (ferro-concrete) where it is necessary to introduce steel. Plain of mass concrete can be used for almost all building purposes. Ferro-concrete us used in buildings bridges and arches, dams and dock-walls, for structured under water, for foundations, columns, girders, beams. The use of concrete and ferro-concrete is almost universal.
Builders now produce two types of new building materials: alkali-slag concrete and silica concrete. In alkali-slag concrete cement is replaced by a mixture of granulated blast-furnace slags and sodium and potassium compounds. The fillers can be sand or sandy loams containing various amounts of clay, which usually cannot be used with conventional cement. The new material has been tested successfully and is now being used for irrigation systems, roads, pavements and other structures.
Silica concrete is light, fireresistant and acid-proof. It contains no cement whatever. Silica concrete is widely used in aviation and in under water constructions.
Vocabulary (2)
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определение быть связанным сходным наполнителем раствор частица быть пригодным приложенные грузы трение просачивание понижать монтажа вредные примеси галька шлак пемза свободный объем ячеистый бетон пениться захватывание воздушные пузырьки стабильный, прочный |
Text (2)
Aggregates for concrete
The term “Concrete” is used to describe a dense material composed of cement and aggregate mixed with water.
Therefore there is a broad division of concrete types into:
a) Dense concretes – composed of heavy aggregates.
b) Light-weight concretes – composed of light aggregates.
By the simple definition from the dictionary "aggregates are the materials, such as sand and small stones, that are mixed with cement to form concrete". In other words aggregates can be defined as a mass of practically inert mineral materials, which, when surrounded and bonded together by an active binder, form the rock. This rock is denoted by the general term concrete.
Aggregates have three principal functions in the concrete:
All aggregates, both natural and artificial, which have sufficient strength and resistance to weathering, and which do not contain harmful impurities may be used for making concrete. As aggregates such natural materials as sand, pebbles, broken stone, broken brick, gravel, slag, cinder, pumice and others can be used.
The aggregates are graded in size from fine to coarse in order to reduce the amount of void space to be filled by cement. There are “cellular” concretes made by using materials which foam of form gas during the mixing of the concrete. These give a product of very light weight, because after setting it contains a large number of small voids.
The reduction in weight is accompanied by a considerable decrease in strength. Another type of light weight concrete is made by “entraining” air bubbles in the mix to which a substance has been added to keep the bubbles stable during setting.
Vocabulary (3)
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главным образом слабый растягивающее напряжение балка быть растянутым прогибаться гнуться край растяжение площадь поперечного сечения пролет внедрять |
Text (3)
Prestressed Concrete
Prestressed concrete is not a new material. Its successful use has been developed rapidly during the last two decades, chiefly because steel of a more suitable character has been produced. Concrete is strong in compression but weak when used for tensile stresses.
If, therefore, we consider a beam made of plain concrete, and spanning a certain distance, it will at once be realized that the beam's own weight will cause the beam to "sag" or bend. This sagging at once puts the lower edge of the beam in tension, and if the cross-sectional area is small, causes it to break, especially if the span is relatively large.
If, on the other hand, we use a beam of similar cross-section, but incorporate steel bars in the lower portion, the steel will resist the tensile stress derived from the sag of the beam, and thus assist in preventing it from breaking.
In prestressed concrete steel is not used as reinforcement, but as a means of producing a suitable compressive stress in the concrete.
Text 4.
Portland-cement Concrete
Portland-cement concrete is a mixture of Portland cement, water, coarse and fine aggregates, and admixtures proportioned to form a plastic mass capable of being cast, placed, or molded into forms that will harden to a solid mass. The desirable properties of plastic concrete are that it is workable, placeable and no segregating, and that it set in the desired time.
The hardened concrete should provide the desired service properties:
1. Strength (compressive and flexural)
2. Durability (lack of cracks, resistance to freezing and thawing and to chemical attacks, abrasion resistance, and air content)
3. Appearance (color, lack of surface imperfections)
Each of these properties affects the final cost of the mix design and the cost of the inplace concrete. These properties are available from normal weight, lightweight, and heavyweight concretes.
Text 5.
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 and 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 19th 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 has 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 of the addition of steel reinforcement to concrete?
Steel does not undergo shrinkage or drying but concrete does and 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 from reinforced concrete the following consideration should be kept in mind:
1. For general use the most suitable proportions of cement and aggregate are: I 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.
Ex.1. Add the missing parts of the sentences from the text
1. ...to produce a mixture of the proper consistency.
2. Concrete is an artificial stone, made by thoroughly...
3. ...they provide a relatively cheap filler for the concreting material, or binder, ...
4. This sagging at once puts the lower edge...
5. ... as a means of producing a suitable compressive stress in the concrete.
6. ... any beam made of pre-stressed concrete is permanently under compression...
7. This sagging at once puts the lower edge....
Ex.2. Find in the text equivalent Russian phrases to the following English
Ex.3. Find in the text equivalent English phrases to the following Russian
Ex.4. Answer the following questions:
1. How is concrete made?
2. What takes place when water is added to the cement?
3. Does the whole mixture set and harden when hydration takes place?
4. A solid mass is formed, right?
5. Do you know what is termed “aggregate”?
6. Is sand known as “fine aggregate”?
7. And what is meant by “coarse aggregate”?
8. Can concrete be made on a building site and poured into position as a wet mix?
9. Are you able to explain what is meant by “in-situ” concrete?
Ex.5. Insert the needed words and groups of words:
Ex.6. Read the following and then describe the behavior of concrete:
1. Curing. Concrete becomes hard by the chemical combination of cement and
water, during which process it is necessary to prevent as far as possible
evaporation of the water from the surface of the concrete; this is called
“curing”, and is accomplished by covering the concrete, as soon as it can be
done without damaging the surface, with damp cloths, wet straw, wet sand, etc.,
kept wet by sprinkling, or by immersing in water.
2. Hardening. The strength of concrete under favorable curing conditions
increases with age. Hardening is very rapid in the early stages, but continues
more slowly for an indefinite period amounting to years.
Ex.7. Study the following text and then give it a title:
Concrete – unlike many buildings materials – is equally a framing and an enclosing material. It can be used to construct a skeleton; it can also be used to construct a complete weather tight shell of floor, walls and roof. In this respect it is one of the few total building materials.
It is hardly surprising that for a long time reinforced concrete was treated in a similar manner to a steel frame, clad in some other material.
Steel needs protection from the external elements and from internal fire; concrete need neither of these. Steel was a construction material of parts connected together; concrete could be handled to produce a monolithic structure including enclosing surfaces.
The present stage of evolution shows and appreciation of concrete as a total material.
Ex.8. Render the text in Russian:
Concrete.
Concrete is an artificial stone. It is made by mixing a paste of cement and water with sand and crushed stone, gravel, or other inert material.
After this plastic mixture is placed in forms, a chemical action takes place and the mass hardens. Concrete, although strong in compression, is relatively weak in resisting tensile and shearing stress which develop in structural members. To overcome this lack of resistance, steel bars are placed in the concrete at the proper positions, and the result is reinforced concrete. In beams and slabs the principal function of the concrete is to resist compressive stresses, whereas the steel bars resist tensile stresses.
Ex.9. Render the following in English:
1. Лёгкие бетоны изготовляют на пористых естественных или искусственных заполнителях.
2. Лёгкие бетоны на пористых заполнителях применяют для изготовления панелей для стен, плит перекрытий и конструкций каркаса.
3. Конструкции из легких бетонов следует применять при отсутствии агрессивных воздействий.
4. Когда конструкции находятся в агрессивной среде (наличие агрессивных газов, паров, кислот и т. д.), мелкие трещины растянутой зоны бетона способствуют активному развитию коррозии арматуры.
5. Это приводит к снижению несущей способности конструкций.
6. Для борьбы с коррозией бетонных и железобетонных конструкций применяют плотные бетоны, кислотостойкие бетоны, полимербетоны.
Ex.10. Fill up the blanks with English equivalents:
1. (Самым важным качеством) of concrete is its property to be formed into large and strong monolithic units.
2. Concrete is made by mixing cement, sand, gravel and water (в нужных количествах).
3. The characteristics of concrete depend (от качества используемых материалов).
4. (Бетон применялся египтянами, римлянами) in the construction of aqueducts and bridges.
5. (Так как цемент не был известен в то время) concrete was made of clay and later of gypsum and lime.
Ex.11. Complete the sentences using the English equivalents for the Russian words in brackets.
1. The resulting material gains great strength when (он затвердевает).
2. At the turn of the 19th century new structural concrete (стал применяться).
3. Steel has great tensional, compressive and elastic properties but (со временем она теряет прочность).
4. Steel does not undergo shrinkage and therefore it acts (как сдерживающая среда).
5. Shrinkage causes tensile stresses in concrete which are balanced (сжимающими усилиями в стали).
Ex.12.Translate into English:
1. Железобетон - это вид бетона, полученного в результате сочетания бетона и стали.
2.Стальные стержни и стальная арматура укладываются в нужном положении и заливаются бетоном.
3. Бетон затвердевает, схватывается и приобретает большую прочность.
4. Сталь не подвергается усадке, она действует как сдерживающая среда в железобетонном элементе.
Ex.13. Complete the sentences:
1. Prefabrication means...
a) … reinforcement of brickwork with steel.
b) … preassembly in a workshop, so that the building can be more quickly erected on the site.
c)... craft operation at the building site.
2. Reinforced concrete is a building material in which...
a) ...such properties as small volume weight and high thermal conductivity are combined.
b) ...physical and mechanical properties at a normal temperature of 20°C make it semi-rigid and soft.
c)...the joint functions of concrete and steel are advantageously utilized.
3. Like any other stone material, concrete offers...
a) …the ability of binding together masonry units such as stone, brick and plaster.
b) … a good resistance to compressive loads.
c) ...a lower volume weight and it is manufactured from a mixture of unslaked lime and quartz sand.
Grammar
Ex.14. Translate the following words using GERUND
a) into English
изучение, тренировка, получение, увеличение, уменьшение, построение, написание, общение, предотвращение, создание.
b) into Russian.
writing-table, computing machine, drawing-table, measuring devices, building materials, dining-room, reading-room, looking-glass, adding machine.
Ex.15. Translate the sentences paying attention to GERUND
1. What I really like is finding out about different cultures.
2. The thing I love most is singhtseeing.
3. The best thing for me is socializing with my friends.
4. Concrete is made by thoroughly mixing cement, sand and gravel.
5. All aggregates may be used for making concrete.
6. The steel will resist the tensile stress and thus assist in preventing the beam from breaking.
7. The term "engineering" means the art of designing, construction or using engines.
8. The ancient Egyptians often erected their huge buildings without thinking of their usefulness.
9. A person can't be successful without clear understanding of goals in his life.
10. It goes without saying.
11. One can't be healthy without giving up bad habits.
Ex.16. State the functions of GERUND in the following sentences and translate them into Russian
1. Cutting stones and timbers became possible with the invention of tools.
2. By using industrial methods of construction the speed of construction may be considerably increased.
3. Erecting tall buildings without using building mechanisms is now unthinkable.
4. Methods of designing structures are changing.
5. Up-to-date building is based upon using industrial methods of work.
6. What other materials are used for facing the external walls of a building?
7. The new method is very efficient and besides it plays an important role in saving materials.
Ex.17. Translate the sentences into English using GERUND
1. Вредно так много курить.
2. Эта статья трудная. Вы не можете перевести ее без использования словаря.
3. Она любила путешествовать по стране.
4. Недолго думая, он согласился с их предложением.
5. Вместо того чтобы реставрировать старый городской драмтеатр, они решили строить новый в центре города.
6. Ничто не могло помешать ему построить новый дом.
7. У тебя есть какая-нибудь трудность в решении этой проблемы?
8. Есть ли у них подходящий строительный материал?
9. Подрядчик отвечает за то, чтобы работа была выполнена вовремя.
TIME FOR FUN
1. Read the small dialogues in pairs
I
Professor: Why are you late?
Student: Class started before I got here.
II
Teacher: Which is farther away, Anthony, the moon or China?
Anthony: China.
Teacher: What makes you think that?
Anthony: Because we can see the moon any clear night and we
can't see China.
III
Father: I see you did very badly in your History examination.
Son: It wasn't my fault. They asked me about things that happened
long before I was born.
Ex.18. Read and try to retell the anecdote changing the Direct
Speech into Indirect.
Once a French cabman played a good joke on Conan Doyle. When Conan Doyle arrived in Paris it was raining heavily. He took a cab and asked the cabman to take him to the Ritz Hotel as he had reserved a room there a few days before.
The cabman brought him to the hotel. When he had received his fare he said, "Thank you, Mr. Conan Doyle". "How do you know my name?" asked Conan Doyle.
"Well, sir," replied the driver, "the other day I saw in the papers that you were coming from the South of France to Paris. Your appearance told me you were British, and I also saw you had had your hair cut in the South of France. So I decided it was you.
"You are a wonderful detective," said Conan Doyle. "Were there any other things about me, that could help you to think it was I?" "Well," said the cabman, "there was also your name on your suit-case, sir".