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.pdfSimultaneous – simultaneously (одновременно).
32. Read the text and answer the questions after it.
Asphalt Materials
Solid or semi-solid, tenacious, viscous bitumens either native or produced from petroleum, which become liquid on the application of the heat are known as asphalts.
Chemically, asphalts are highly complex. They are termed native or natural asphalts when found existing in nature, and oil asphalts when artificially prepared from petroleum.
Asphalt materials consist of stone materials (broken stone or gravel, sand and mineral powder) and bitumen.
Asphalt materials are widely used in road makings and less for other purposes. In road making asphalt materials are used for constructing road surfacing.
Asphalt materials are classified as to their composition, properties and purposes these materials are used for. According to the purposes asphalt materials are divided into road, hydroinsulating and mixtures for special purpose. Road asphalt materials containing broken stone or gravel possessing high mechanical properties are named asphalt concretes.
Hydroinsulating mixtures possess high waterproofness. They are mostly used in the form of asphalt solutions, mastics, putties. Asphalt concrete which works as the material of road surfacing undergoes different mechanical influences caused by the transport. This results in the appearing of stresses of different character and of different amount within the material. That is why the concrete must offer sufficient resistance to compression, tension, rubbing and besides this it must possess plastic and elastic properties, absorbing these stresses and causing no damage to the surfacing.
Mechanical properties of asphalt concrete may change depending on temperature. That is why it is necessary that at given amplitude of fluctuation of temperature the change of mechanical property is within the certain limits, in other words it is necessary that asphalt concrete possesses sufficient temperature stability. Simultaneously with the mechanical influences the asphalt concrete in the road surfacing undergoes destructive influence of atmosphere factors (water, air etc.).
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To achieve the minimum influence of these factors asphalt concrete is to possess sufficient compactness and to consist of materials of proper quality.
The necessary technological property of asphalt concrete mixtures is easiness of treating these mixtures. The main method of treating asphalt mixtures is distributing them in a layer of uniform thickness over the road bed foundation and consolidating them with the help of rollers (rigid type) or levelling with the help of a wood float (cast type of mixture). According to the chosen method of treatment the mixtures must be of proper consistence at the operating temperature. Thus the most principal technical properties of asphalt concrete are mechanical durability, compactness and easiness of treating.
Except above mentioned properties which are considered to be the main properties some special qualities are sometimes required of asphalt concrete.
In some cases asphalt road surfacing is required to be more rough than usual to reduce slipperiness or to have definite colour for the purpose of making disjunctive strips, curbs, etc.
Cost of asphalt concrete mixture must be low. It depends on the components cost (especially on the expenditure of the most expensive materials of the mixture - bitumen and mineral powder). and on the production factors. Utulizing local materials, rational work organization, full mechanization of production process, advanced methods of work are the ways of reducing the asphalt concrete mixture unit cost.
Cold asphalt concrete mixtures differ from hot ones because they may be applied at the normal temperature (15° – 25°) without being heated.
Cold asphalt mixtures are classified according to the nature of the component materials and the method of preparation.
Depending on the nature of binder cold mixtures may be asphalt mixtures (with application of bitumen) and tar mixtures (with application of tars).
When utilizing asphalt rocks it is possible to get natural cold asphalt materials. Artificial mixtures are produced by means of the application of crushed stone materials and liquid bitumen, and tars or emulsions.
Mechanical properties of cold fine-grained asphalt depend on binder viscosity, thickness of enveloping film, properties of stone frame and mixture compactness. Mechanical properties of cold asphalt mixtures are determined according to resistance the cylinder shaped patterns of h = 50 mm, d = 50 mm offer to compression.
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1.What materials are known as asphalts?
2.What does asphalt consist of?
3.How many groups of asphalt materials do you know? Name them.
4.What is asphalt concrete?
5.What is the necessary technological property of asphalt concrete mixtures?
6.When may cold asphalt concrete mixtures be applied?
7.Why must the concrete possess plastic and elastic properties?
33.Read and study the following words. Make word-combinations with them:
admixture – примесь, добавка; brittle – хрупкий;
clayey – глинистый;
coherency – связность, сцепление; ground asphalts – грунт-асфальт; loamy – глинистый;
powdered soil – пылеватый грунт; saturate – насыщать, пропитывать.
34. Explain the name of this building material, then read the text and check your explanation.
Groundasphalt
Ground asphalts are asphalt mixtures which comprise natural soils as mineral materials sometimes with the addition of sand or gravel and bitumen or tar as a binder.
Utilisation of natural (clayey) loamy and powdered soils as road building materials for making road surfacings is difficult because their mechanical properties are not constant under variable humidity and sand is inconvenient to use because it possesses no coherency.
Some soils are very unstable, grinding to dust easily when dry or quickly turning to mud when wet and hence the roads are difficult to maintain.
In the period of excess humidity (autumn rains, snow melting etc.) loamy and powdered grounds get saturated with water and lose the necessary mechanical properties. In the droughty period they get dry, become
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brittle and as a result of this they wear out and become dusty. Sand roads offer great resistance to traffic because of their looseness though they do not get saturated.
Various methods have been tried to stabilize such soils. Stabilizers are of two types, those that act purely as a mechanical admixture with the soil and those that have a direct action oil the soil itself.
Among many methods of stabilization of soils treatment with organic binders is considered to be the most perfect.
35. Answer the questions.
1.What is the essential constituent of ground asphalts?
2.Why are such roads difficult to maintain?
3.How can unstable soils be stabilized?
4.What is the most perfect method of soil stabilization?
36. Translate the following words keeping in mind their suffixes and prefixes. Define their part of speech.
Mix, mixable, mixed, mixer, mixing, mixture, premix, unmixed. Stable, stability, stabilize, stabilized, stabilizing, unstable, unstabi-
lized.
Vary, varying, variable, variability, variant, varied, unvarying.
37. Read the text to answer the question “What are the main kinds of articles made of asphalt concrete?”
Asphalt concrete articles
The principal kinds of articles made of hot asphalt concrete and seldom of tar concrete are slabs, chesses and pipes. Slabs and chesses are used as building materials for paving the roadways, streets, bridges, surfacing between tram rails, and sidewalks. For making the asphalt concrete slabs only fine-grained asphalt concrete and sand asphalt are used. The materials composing the asphalt concrete mixture used for making slabs, bitumen excluding, must be chosen in the accordance with such technical requirements as for common asphalt concrete used in hot state.
While choosing the properties of bitumen used for asphalt concrete slabs it is necessary to take into consideration the peculiarities of making (moulding) slabs and their work in surfacings.
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38. Read the sentences, define the initial form of the words in bold and their part of speech. Then find relevant meanings of these words in a dictionary.
1.a) The road was in a pure state.
b)The former colony became an independent state.
2.a) He likes playing chess.
b)Bridges and sidewalks are often paved by chess.
3.a) The principal of our school is a rather young man.
b)The principal sphere of our activity is development of new building materials.
4.a) This article was published in “The Times”.
b)The shop sells articles of clothing.
5.a) Many plants have medicinal properties.
b)The police found some stolen property hidden in the thief’s house.
39. Complete the sentences using information from the text.
1.Slabs and chesses are used as building materials for paving … .
2.Only fine-grained asphalt concrete and sand asphalt are used for making … .
3.The peculiarities of moulding asphalt concrete slabs must be taken into consideration while choosing … .
4.Slabs, chesses and pipes are seldom made of … .
40. Read the additional text and give its short summary. Try to guess when this text was written. Why do you think so?
Use of wood
Except the materials already described we also use wood -for road making. At present wood is one of the most widespread building materials in different fields of national economy. The total area of woods in Russia occupies 30% of the whole territory of the country.
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Great reserves of wood, the comparatively simple method of exploiting large forests, easy machinability of wood and the significant development of the technique of wood working are the main reasons of wood being widely used in engineering. Wood as building material possesses some valuable properties. Being highly resilient and durable, easily worked wood has little volumeritrical weight which makes transportation easier and conditions the low weight of wooden constructions. But these advantages may be reduced to some extent by some negative properties characteristic for wood.
The main defects of wood are: the changing of mechanical properties depending on humidity; some species of trees have also insufficient hardness; when dry wood can produce cracks; wood undergoes rotting and damage by insects; wood catches fire easily.
Wood is used for making bridges, pipes, blocks for road surfacing. Buildings and other structures may also be made of wood.
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HIGHWAY USAGE AND MAINTENANCE
1. Read and translate the text. Underline the key sentence in each paragraph.
Main principles of the highway usage
The main task of the usage of the motor-car and the highway is achieving high speeds of the cars on the highways together with the assuring the comfort and safety of traffic with the most possible safety for a motor-car and highway. This problem becomes especially important with the increasing of automobile speed and with the development of high speed road construction.
Depending on the demands of the motor car traffic the main indices of usage fixed for the highways are:
a)the designed speed of movement,
b)the designed weight of motor-cars.
These indices are set while designing or reconstructing the highway and must be followed up to the mark during the process of usage. One of the most important problems of the road usage is the estimate of the surfacing upper layer state.
Not only evenness but smoothness, dustiness and noisiness as well play an important role in estimating the quality of surfacing.
But all these surfacing properties influence the amount of possible traffic speed far less than the evenness rate. Surfacing quality influences fuel consumption, rubber wear, motor car depreciation and consequently the working cost of the motor-car transportations.
The coefficient of service is the index of surfacing state. Every road must have a fixed value of service coefficient, beneath which the usage service department must not allow any reduction of road quality.
For the trunk highways and for the roads of special importance the coefficient of service must be not less than 1.
The constructed road with all the road constructions is put into operation and the repair and maintenance service is organized on the road. Therefore the road usage, maintenance and repair are closely connected.
The ensuring of such a state of the road which can in the best way satisfy all the traffic demands is achieved by the whole system of technical measures for road maintenance and repair.
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2. Read and study the following words:
evenness – ровность;
smoothness – ровность, гладкость, плавность; longitudinal section – продольный профиль; cross-section – поперечный профиль;
fuel – топливо;
surface – поверхность, покрытие; trunk – магистраль;
satisfy – удовлетворять;
demand – требование, потребность.
3. Fill in the gaps with the words from the text.
1.The main task of the usage of the motor-car and the highway is
___________of the high speeds of the cars on the highways together with the assuring the comfort and safety of traffic.
2.___________ on the demands of the motor car traffic the main indices of usage fixed for the highways are: a) the designed __________, b)
___________ of motor-cars.
3. _________ evenness but _________, __________ and __________
as well play an important part in estimating the quality of surfacing.
4.All these surfacing properties _________ the amount of possible traffic
_______ far less than the ______ rate.
5.Every road must have _______ ___________ of service coefficient.
6.The coefficient of service must be not less than 1 for the __________
highways and for the roads of ___________ .
7.Maintenance, repair and ________ ___________ are closely connected.
4. Find the false sentences using the information from the text. Correct them.
1.The main task of usage of the motor-car and the highway is achieving of the high speeds of the cars as well as safety of traffic.
2.The estimation of the surfacing upper layer state is the only important problem of the road usage.
3.Smoothness, dustiness and noisiness influence the traffic speed more than evenness rate.
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4.Expenditure of fuel, rubber wear, motor car wear depend on the surfacing evenness.
5.The coefficient of usage is the index of surfacing state.
6.For the trunk highways and for the roads of special importance the coefficient of service must be not less than 1.
7.Road usage, maintenance and repair are closely connected.
5. Answer the following questions.
1.What is the main task of the usage of the motor-car and the highway?
2.What influences the amount of possible traffic speed?
3.What is the one of the most important problems of the road usage?
4.What is the coefficient of service?
5.How must the state of the road which can satisfy all the traffic demands be achieved?
6.Give the English equivalents:
как уже было упомянуто; с наиболее возможной безопасностью;
в зависимости от потребностей; не только ровность, но и гладкость; все это влияет на; следовательно; поэтому; тесно взаимосвязаны; целой системой.
7. Choose the right form of the verb.
1.The main task of the usage of the motor-car and highway is
___________ of the high speeds of the cars. a) achieving
b) to achieve c) achieve
2.One of the most important problems of the road usage is _________ of the surfacing upper layer state.
a) the estimate
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b)the estimation
c)estimating
3.All these factors _________ the amount of traffic speed. a) influence on
b) influence
c) were influenced by
4.Every road _________ a fixed value of service coefficient. a) must has
b) must have c) should have
5.This _________ by the whole system of measures.
a)are achieved
b)is achieved
c)achieved
8.Ask your friend to tell you about main principles of the highway usage.
9.Read the text and say what facts mentioned in it you have never heard before. Compare your answers with the information got at Physics lessons.
Principles of Road Usage
The Influence of Road upon Automobile. When any vehicle is moving along the road there appears the interaction between the vehicle and the road.
The wheels of the rolling stock influence the road (road surfacing) directly creating the horizontal and vertical efforts on the road surfacing.
All this causes rubbing out the surfacing. The more the weight and speed of the traffic and the more rigid the wheels and parts of the rolling stock the more intense the influence of the wheels upon the surfacing.
The road surfacing in its turn has the definite influence upon the rolling stock, causing the resistance to the movement, the impacts, vibration of some parts of the vehicles, the sliding of the wheels. The interaction of the rolling stock with the road results in the gradual wearing and damaging some parts of vehicles as well as those of the road.
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