Create three groups. Each group chooses one material from this unit (stone, timber and concrete). Use your own words to describe it to the other groups.

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Disadvantages of timber.

·Timber is vulnerable (уязвимый) to vital forces like termites (термиты), woodworms (личинки древоточца) or wood ants (муравьи).

·Natural forces like the sun, fire, water and etc. can have unfavorable effect on timber.

·Timber is subjected to shrinking (усадка) and swelling (набухание, вспучивание). Timber has a natural ability to absorb water which is also known as hygroscopy.

CONCRETE

Concrete is an artificial stone-like material used for various structural purposes. It is made by mixing a binding material as cement and various aggregates i.e. inert materials, such as sand, crushed stone, pebbles (галька, мелкий булыжник), gravel, shale, etc with water and allowing the mixture to harden by hydration (гидратация – присоединение воды к ...).

Advantages of concrete.

· Concrete is economical when ingredients are readily available.

· Long life of concrete and relatively low maintenance requirements increase its economic benefits.

· It is not subjected to corrosion or decay as other building materials.

· Concrete has the ability to be moulded or cast into almost any desired shape.

Concrete is non-combustible material which makes it fire-safe and able to withstand high temperatures

· It is resistant to wind, water, and insects. Therefore, concrete is often used for storm shelters.

Disadvantages of concrete.

· Concrete has a relatively low tensile strength compared to other building materials.

· Low ductility.

· Low strength-to-weight ratio.

· Concrete is subjected to cracking (трещинообразованию).

2.  Use the information from the texts to complete the following table.

stone

timber

concrete

advantages

disadvantages

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