1) Decide whether the statements are true or false:

1. Stones are cheaper than bricks.

2. Nowadays stones are only used as aggregates for concrete.

3. Stones were never used for heavy engineering.

4. Quartzite is not used for ornamental work because it is soft.

5. Laterite is used for walls and paving.

2) Match the words from the left with their Russian equivalents:

Marble Limestone Slab Pier Aggregate

Известняк Заполнитель Опора Мрамор Плита

3) Guess the word by its definition:

1. A structure that supports a building

2. Small blocks of clay used in building

3. A building or place of shelter to live in

4. A large, thick, flat piece of stone

5. A shiny silicate mineral found in granite and other rocks

4) Open the brackets and put the verbs in a correct form:

1. People (use) stones to build dwellings from early times.

2. Stones (use) for heavy engineering constructions before the invention of concrete.

3. Geology (study) rock-forming minerals.

4. Most prehistoric monuments (build) of stones.

5. Granite often (cut) into slabs.

References: http://books.google.ru/books?id=MBamtq45OykC&printsec=frontcover#v=onepage&q&f=false

Unit 7. Concrete.

Vocabulary.

Aggregate – заполнитель

Diluted – разбавленный

Cure – затвердевать

Imperviousness – герметичность

Mouldability – способность к формованию

Concrete is a building material made by mixing cement (portland cement and water) with aggregate (sand and stone). The cement is the ‘glue’ that binds the particles in the aggregate together. The strength of the cement depends on the relative proportions of water and cement, with a more diluted paste being weaker. In addition, the relative proportions of cement and aggregate affect the strength, with a higher proportion of making stronger concrete. The concrete hardens through the chemical reaction between water and cement, without the need for air. Once the initial set has taken place, concrete cures well under water. Strength is gained gradually, depending on the speed of the chemical reaction. Admixtures are sometimes included in the concrete mix to achieve certain properties. Reinforcement steel is used for added strength, particularly for tensile stresses. Concrete is normally mixed at the building site and poured into formwork of the desired shape, in the position that the unit will occupy in the finished structure. Units can also be precast, either at the building site or at a factory.

Concrete is associated with high strength, hardness, durability, imperviousness and mouldability. It is a poor thermal insulator, but has high thermal capacity. Concrete is not flammable and has good fire resistance, but there is a serious loss of strength at high temperatures. Concrete made with ordinary portland cement has low resistance to acids and sulphates but good resistance to alkalis.

Answer the questions:

1. What does the strength of the cement depend on?

2. What is required for curing of concrete?

3. What kind of admixtures can be used in the concrete mix?

4. What are the properties of concrete?

5. How does high temperature affect concrete?

Exercises: