Make up a detailed plan of the text.

I. Answer the questions:

- What road construction materials do you know?

- What materials are the most commonly used in Russia?

- Describe the condition of the Russian roads. What measures are to be taken to improve the situation?

The general classification of road materials: asphalt concrete

New words and phrases to learn:

amount of traffic - пропускная способность дороги

weight of the vehicle – вес транспортного средства

general requirements – общие требования

mechanical strength – механическая сила

compactness – плотность

porosity – пористость

viscosity – вязкость

stability – устойчивость

asphalt concrete – асфальтобетон

composite material – композитный материал

asphalt binder – асфальт раствор

mineral aggregate – минеральная смесь

moisture – влажность

consumption – потребление

fossil fuel – ископаемые виды топлива

carbon dioxide – двуокись углерода

vapours – испарения

patching material – заполнитель

to dissolve – растворять

to evaporate - испаряться

1.  Read and translate the text:

Roads are constructed from a variety of  materials. The material used depends on local conditions and other factors such as the amount of traffic the road is designed for and the weight of the vehicles allowed to use the road. The road construction materials should keep to general requirements such as mechanical strength, compactness, porosity, viscosity and stability. The most commonly used materials are: asphalt concrete of any type; bitumen; cobblestones; crushed stones; concrete; chipseal.

The production of the road construction materials requires the development of the special modern technologies to provide the roads with the higher level of safety index.

• Asphalt concrete

Asphalt concrete, normally known simply as asphalt, is a composite material commonly used for construction of pavement, highways and parking lots. It consists of asphalt binder and mineral aggregate mixed together then laid down in layers and compacted. Mixing of asphalt and aggregate is accomplished in one of several ways:

Hot mix asphalt concrete (commonly abbreviated as HMAC or HMA) is produced by heating the asphalt binder to decrease its viscosity, and drying the aggregate to remove moisture from it prior to mixing. Mixing is generally performed with the aggregate at about 150 °C for virgin asphalt and 166 °C for polymer modified asphalt, and the asphalt cement at 95 °C. HMAC is the form of asphalt concrete most commonly used on highly trafficked pavements such as those on major highways, racetracks and airfields.

Warm mix asphalt concrete (commonly abbreviated as WMA or WAM) is produced by adding either zeolites, waxes, or asphalt emulsions to the mix. This allows significantly lower mixing and laying temperatures and results in lower consumption of fossil fuels, thus releasing less carbon dioxide, aerosols and vapours. Not only are working conditions improved, but the lower laying-temperature also leads to more rapid availability of the surface for use, which is important for construction sites with critical time schedules. The usage of these additives in hot mixed asphalt (above) may afford easier compaction and allow cold weather paving or longer hauls.

Cold mix asphalt concrete is produced by emulsifying the asphalt in water with (essentially) soap prior to mixing with the aggregate. While in its emulsified state the asphalt is less viscous and the mixture is easy to work and compact. The emulsion will break after enough water evaporates and the cold mix will, ideally, take on the properties of cold HMAC. Cold mix is commonly used as a patching material and on less trafficked service roads.

Cut-back asphalt concrete is produced by dissolving the binder in kerosene or another lighter fraction of petroleum prior to mixing with the aggregate. While in its dissolved state the asphalt is less viscous and the mix is easy to work and compact. After the mix is laid down the lighter fraction evaporates.

Mastic asphalt concrete or sheet asphalt is produced by heating hard grade blown bitumen (oxidation) in a green cooker (mixer) until it has become a viscous liquid after which the aggregate mix is then added.

Natural asphalt concrete can be found in some parts of the world where rock near the surface has been impregnated with upwelling asphalt.

Rubberized Asphalt Concrete (RAC), also known as Asphalt Rubber, is pavement material that consists of regular asphalt concrete mixed with crumb rubber - ground, used tires that would otherwise be discarded or take up space in landfills.

2. Answer the questions:

- Give the definition of asphalt concrete.

- How many types of asphalt concrete mixes do you know? What’s the difference between them?

- What type of asphalt concrete is the easiest to work with? Why?

- The material used for road construction depends on the price of its manufacturing. This is a main criteria for the choice of the construction material.

- Asphalt concrete consists of asphalt binder and mineral aggregate mixed together then laid down in layers and compacted.

- There are 7 types of asphalt concrete mixes.

- Cold mix asphalt concrete is used to repair roads in winter and in rainy seasons.

- Natural asphalt concrete can be found in some parts of the world where rock near the surface has been impregnated with upwelling asphalt.

Мы поможем в написании ваших работ!