TEXT 5. Sustainable materials

 

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Due to the rise in global population and prosperity over the last few decades, one of the consequences of this phenomenon has been the increase in volume and variety of the materials used (such as raw materials, food, manufactured products and waste) with a consequent increase in the transport distances. This has created a series of negative effects on the environment, especially different kinds of pollution, leading to an ecological emergency and growing preoccupation about health. This is why the aim of eco-design is to create buildings with low ecological impact, where people can live in a comfortable, healthy way. This is possible by using building materials that are traditionally considered eco-friendly and-sustainable: timber from forests that have been certified; quickly renewable plant materials (such as straw or bamboo); some typical traditional materials such as brick, stone, clay and cork; non-toxic, renewable and recyclable materials (natural paints, waxes and varnishes). Waste materials can also be reused as a resource for construction purposes.

 

1.  What has happened to population and wealth in the last few decades?

2. What has been one of the results of this?

3. What is the aim of eco-design?

4. Can you name some eco-friendly and sustainable materials you have found in the text?

2. Ответьте на вопросы (работа в парах):

What is your opinion of modern building materials? Which would you use if you could build your own house? Tell your partner about it using the information given in this unit.

VIII. AGGREGATES FOR CONCRETE

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AGGREGATES FOR CONCRETE

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AGGREGATES FOR CONCRETE

By the simple definition from the dictionary “ aggregates are the materials, such as sand and small stones, that are mixed with cement to form concrete”. In other words aggregates can be defined as a mass of practically inert mineral materials, which, when surrounded and bonded together by an active binder, form a rock. This rock is denoted by the general term concrete.

Aggregates have three principal functions in the concrete: they provide a relatively cheap filler for the concreting material, or binder; they provide a mass of particles which are suitable for resisting the action of applied loads, of abrasion, of percolation of moisture through the mass, and of climate factors; they reduce volume changes resulting from the action of the settin g and hardening of the concrete mass.

All aggregates, both natural and artificial, which have sufficient strength and resistance to weathering, and which do not contain harmful impurities may be used for making concrete. As aggregates such as natural materials as sand. Pebbles, broken stone, broken brick, gravel, slag, cinder, pumice and others can be used.

Sand is the chief material used as a fine aggregate. It is required in mortar or concrete for economy and to prevent the excessive cracking. Mortar made without sand would be expensive.

     The word “sand” is applied to any finely divided material, which will not injuriously affect the cement or lime and which is not subject to disintegration or decay. Sand is almost the only material which is sufficiently cheap and which can fulfill these requirements.

     A mixture of coarse and fine grains is very satisfactory, as it makes a denser and stronger concrete with a less amount of cement than when only fine-grained sand is used.

     The following sands are used for mortars: quarry sand, river sand and sea sand.

 

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” AGGREGATES FOR CONCRETE ”