A smooth mixture of lime sand water etc that becomes hard when dry and is used for making a smooth s...: ответ на тест 30168 - Английский язык

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Nowadays a building’s framework is made of reinforced concrete and of structural steel. Concrete is made by mixing together small stones, sand, cement and water. The coarse stones used in the mix give the concrete its strength. The sand is needed to fill the gaps between the stones. The cement, mixed with just enough water to make it into a paste, covers the surface of all solids, and binds the entire mixture into single mass. It is used less water to make mixing concrete denser and stronger. It is a difficulty here. Dry mixing concrete is not so easy to stir as one that is fairly wet and sloppy. When it is really strong concrete, it is mixed with the necessary minimum of water and placed in the forms. After this it is vibrated with electrically vibrated bars. The mixture is tipped or piped into forms (wooden mold) of the shape required.
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The sand is needed …

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Nowadays a building’s framework is made of reinforced concrete and of structural steel. Concrete is made by mixing together small stones, sand, cement and water. The coarse stones used in the mix give the concrete its strength. The sand is needed to fill the gaps between the stones. The cement, mixed with just enough water to make it into a paste, covers the surface of all solids, and binds the entire mixture into single mass. It is used less water to make mixing concrete denser and stronger. It is a difficulty here. Dry mixing concrete is not so easy to stir as one that is fairly wet and sloppy. When it is really strong concrete, it is mixed with the necessary minimum of water and placed in the forms. After this it is vibrated with electrically vibrated bars. The mixture is tipped or piped into forms (wooden mold) of the shape required.
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The sand is needed …

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Easy Metal Designs of Building
1. A basic fast construction for buildings is a metal skeleton. There metal vertical racks and horizontal crossbar with the help of bolt connections gather in cross-section frames. The cross-section frames are a system of extensions or communications, giving to design settlement durability fastens. Then roofing, wall runs, frames under windows, doors are established. Thus a bearing skeleton is ready. Further it is possible to use any facing. It can be ferro-concrete, bricklaying, special panels such as «sandwich», any combinations of the specified designs. In a «sandwich» panel every panel consists of two sheets of the zinced iron between which a special heater is placed. The design has no internal skeleton. Its durability is reached due to the certain orientation of fibers.
2. The scope of fast metallic construction is very wide. They are used at the construction of any industrial targets, warehouses, sports complexes. Recently fast construction designs are used in the market. This process makes metallic construction attractive in the field of trading constructions. A cost of a building from a metallic construction is 30-40% less, than on construction of a similar building, using traditional materials.
3. Today a fast metallic construction is a leader among all building designs, first of all, because of its low price. On the other hand, it has the shortest terms of erection. The economy of time can become very significant and essentially important for any customer. Besides the price and terms of assembly, fast metallic constructions have more important advantage. The matter is that a metallic construction is not only quickly gathered, but also can be disassembled fast and without special financial expenses.
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Planned Economies
1. Planned economies are sometimes called «command economies» because the state commands the use of resources that are used to produce goods and services as it owns factories, land and natural resources. Planned economies are economies with a large amount of central planning and direction, when the government takes all the decisions; the government decides production and consumption. Planning of this kind is obviously very difficult and the result is that there is no society, which is completely a command economy. The actual system employed varies from state to state, but command or planned economies have a number of common features.
2. Firstly, the state decides precisely what the nation is to produce. It usually plans five years ahead. It is the intention of the planners that there should be enough goods and services for all. Planners are afraid to produce goods and services unless they are sure substantial amounts will be purchased. This leads to delays and queues for some products.
3. Secondly, industries are asked to comply with these plans and each industry and factory is set a production target to meet. If each factory and farm meets its target, then the state will meet its targets as set out in the five-year plans. You could think of the factory and farm targets to be objectives, which, if met, allow the nation's overall aim to be reached.
4. A major problem faced by command or planned economies is that of deciding what to produce. Command economies tend to be slow when responding to changes in people's tastes and fashions. Planners are likely to underproduce some items as they cannot predict changes in demand. Equally, some products, which consumers regard as obsolete and unattractive, may be overproduced.
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Plastic Materials
1. Plastic materials are not found in nature. Plastic is formed by extrusion or injection molding under very high pressure. It can be molded into any desired shape. Organic plastics are divided into two general groups: thermosetting and thermoplastic. The thermosetting group becomes rigid through a chemical change that occurs when heat is applied. These plastics cannot be remolded. The thermoplastic group remains soft at high temperatures and must be cooled before becoming rigid. This group is not used generally as a structural material.
2. Plastics are rapidly becoming important construction materials because of their great variety, strength, durability and lightness. Plastics are light. The benefits of light weight coupled with good strength and absence of corrosion offer tremendous potential as alternatives to traditional building materials. A given volume of polythene weights less than one-eighth of an equal volume of iron and less than half of the same volume of aluminum.
3. Plastics are used in the industry and in the household: from rockets and electronics to toys and house ware. Plastic products offer many advantages over the materials they replace, such as ease of handling, lower maintenance costs and rapidity of assembly. The insulation and dielectric properties of plastics led to their early use in the electrical engineering industry, which was followed by special application in mechanical engineering.
4. Using of plastics as materials for a construction in the form of sheets, rods or tubes is substituting the conventional metals. Plastics offer a lot of properties for the designs. Plastics have now been developed to such an extent that they can be applied to almost every branch of building, from the laying of foundations to the final coat of paint.
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Building Construction
1. Building construction has its own history, which is marked by a number of trends. One of these trends is increasing durability of the materials. The first building materials were perishable such as leaves, branches and animal hides. Later people began to use more durable natural materials such as clay, stone, timber. Finally, synthetic materials such as bricks, concrete, metals, plastics were used in building.
2. Another trend is quest for buildings of greater height and span. It was possible by the development of stronger building materials and by knowledge of how materials behave and how to exploit them to greater advantage. The third trend involves the degree of control exercised over the interior environment of buildings: increasingly precise regulation of air temperature, light and sound levels, humidity, air speed.
3. All factors that affect human comfort become possible. A modern trend is change in energy of the construction progress, starting with human muscle power and developing toward the powerful machinery.
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