Read and translate about Portland cement

• concrete

• component measuring

• construction

• technology

• proportion

• building

4. Reading for general meaning. Read and answer the following questions to the text:

• What is a modern technology?

• What materials' forms are very important in all masonry structures?

• What factors must the civil engineer consider?

• What can you tell something about the most accurate method of measuring proportions?

• What kind of material is the most widely used for the purpose of binding together masonry units such as a stone and a brick?

• What material is also known to be the most important com­ponent of concrete?

• What kind of material may be considered an artificial conglomerate of crushed stone?

• What can you tell about an important class of cement?

• What is high aluming cement?

• What materials are mostly used in Russia?

• What can you tell about building technology in Russia?

Building materials are very important in the construction. But it is more important for any designer to select and adapt such building materials of construction that will give the most effective result by the most economical means. In this choice of materials for any work of constructions many factors must be considered by the civil engineer. These factors include availability, cost, physical properties of materials and others.

Practically, all buildings materials have their advantages and disadvantages. That's why some materials are used most widely in building construction for the purpose of binding together masonry units. Among them are lime, gypsum and cement. Last material forms very important elements in all masonry structures, such as stone, a brick. Since the time of its introduction a gradual improvement of Portland cement quality has led to the elaboration of rapid hardening Portland cement, or «high early strength». Portland cement like other materials can be modified to suit a particular application. Later developments include low heat and sulphate resisting cements. The scope for such purpose - made cements has led to the development of an increasing variety such as high alumina cement, blast-furnace slag. They may be also white and coloured cements. Alumina cement has an extremely high rate of strength increase. Portland blast-furnace cement has greater resistance to some forms of chemicals.

So, cement is the most important component of concrete. Concrete is even less uniform than many other materials. Concrete may be considered an artificial conglomerate of "crushed stone, gravel or similar inert material with a mortar". A mortar is a mixture of sand, screenings or similar inert particles with cement and water. It is very important to know everything about proportions. The most accurate method of measuring proportions is to weigh the required quantities of each material. This may be done whether the proportions are based upon volumes or weights. This method is being extensively used in road construction and in many central mixing and in central proportioning plants. It is also widely used in large building constructions. Sometimes timber, steel and concrete are all vary over considerable ranges in the properties desired by the engineer. Even steel varies considerably in its microstructure.

6. Read the text again and complete the following sentences: