Make up a detailed plan of the text.
Retell the text according to your plan.
1.2 The general classification of road materials:
Bitumen, cobblestones, crushed stones
New words and phrases to learn:
organic liquid – жидкость органического происхождения
carbon disulfide – дисульфид углерода
crude bitumen – битум природного происхождения
tar-like form – смолистое вещество
molasses – патока
residual fraction – остаточная фракция
mortar – раствор
to bind – связывать (о компонентах)
substitutes - заменители
1. Read and translate the text:
- Вitumen
Bitumen is a mixture of organic liquids that are highly viscous, black, sticky, entirely soluble in carbon disulfide, and composed primarily of highly condensed polycyclic aromatic hydrocarbons.
Naturally occurring or crude bitumen is a sticky, tar-like form of petroleum which is so thick and heavy that it must be heated or diluted before it will flow. At room temperature, it has a consistency much like cold molasses. Refined bitumen is the residual (bottom) fraction obtained by fractional distillation of crude oil. It is the heaviest fraction and the one with the highest boiling point, boiling at 525 °C .
Most bitumens contain sulfur and several heavy metals such as nickel, vanadium, lead, chromium, mercury and also arsenic, selenium, and other toxic elements. Bitumens can provide good preservation of plants and animal fossils.
- Cobblestone
Cobblestones are stones that were frequently used in the pavement of early streets.
Note that Cobble is a generic geological term for any stone having dimensions between 2.5–10 inches. Cobblestones are typically either set in sand or similar material, or are bound together with mortar. Paving with cobblestones allows a road to be heavily used all year long. It prevents the buildup of ruts often found in dirt roads. It has the additional beneficial advantage of not getting muddy in wet weather or dusty in dry weather. A disadvantage is that carriage wheels, horse hooves and even modern automobiles make a lot of noise when rolling over cobblestone paving.
Cobblestones set in sand have the environmental advantage of being permeable paving, and of flexing rather than cracking with movements in the ground.
· Crushed stone
Crushed stone is one of the most accessible natural resources, and is a major basic raw material used by construction, agriculture, and other industries. Despite the low value of its basic products, the crushed stone industry is a major contributor to and an indicator of the economic well-being of a nation. The demand for crushed stone is determined mostly by the level of construction activity, and, therefore, the demand for construction materials.
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Stone resources of the world are very large. High-purity limestone and dolomite suitable for specialty uses are limited in many geographic areas. Crushed stone substitutes for roadbuilding include sand and gravel, and slag. Substitutes for crushed stone used as construction aggregates include sand and gravel, iron and steel slag, sintered or expanded clay or shale, and perlite or vermiculite.
Crushed stone is a high-volume, low-value commodity. The industry is highly competitive and is characterized by many operations serving local or regional markets. Production costs are determined mainly by the cost of labor, equipment, energy, and water, in addition to the costs of compliance with environmental and safety regulations.
2. Answer the questions:
- Give the definition of bitumen.
- Is there any difference between the terms crude bitumen and refined bitumen?
- What chemical elements does bitumen contain?
- What is a main reason of paving roads with cobblestones?
- What is a disadvantage of paving roads with cobblestones?
- Why is the crushed stone production referred to as an indicator of the economic well-being of the country?
- Enumerate the factors determining the crushed stone production cost.
3. Find Russian equivalents for:
- highly condensed polycyclic aromatic hydrocarbons
- preservation of plants and animal fossils
- generic geological term
- buildup of ruts
- additional beneficial advantage
- the most accessible natural resources
- high-purity limestone
- construction aggregates
- low-value commodity
- costs of compliance with environmental and safety regulations
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