3. Read the following sentences and divide them into three groups ‘Concrete’, ‘Brick’ and ‘Plastics’.

1. There are some kinds of structural materials that have appeared comparatively recently, sometimes they consist of one polymer. But in building industry some complex materials consisting of a polymer and other components are used.

2. In many cases bricks too are very satisfactory for use in the construction.

3. There are some kinds of materials which are brittle and cannot withstand tensile stress.

4. If steel is introduced into some kind of material it changes its property.

5. Some building materials offer a good resistance to compressive loads.

6. In respect of physical and mechanical properties these materials are divided into rigid, semi-rigid and soft.