Опубликовано 6 лет назад по предмету
Английский язык
от Studentos13T
Перевод на украинский
REINFORCED CONCRETE Reinforced concrete is a combination of two of the strongest structural (building) materials: concrete and steel. This term is applied to a construction in which steel bars or heavy steel mesh are properly embedded in concrete. The steel is put in position and concrete is poured around and over it, and then tamped in place so that the steel is completely embedded. When the concrete hardens and sets, the resulting material gains great strength. This new structural concrete came into practical application at the turn of the 19th century. The first results of the tests of the reinforced concrete beams were published in 1887. Since that time the development of reinforced concrete work has made great progress. And the reasons of this progress are quite evident. Concrete has poor elastic and tensional properties, but it is rigid, strong in compression, durable under and above ground and in the presence or absence of air and water, it increases its strength with age, it is fireproof. Steel has great tensional, compressive and elastic properties, but it is not durable being exposed to moisture, it loses its strength with age, or being subjected to high temperature. So, what is the effect of addition of steel reinforcement? Steel does not undergo shrinkage or drying but concrete does and therefore the steel acts as a restraining medium in a reinforced concrete member. Shrinkage causes tensile stresses in the concrete which are balanced by compressive stresses in the steel. For getting the best from reinforced concrete the following consideration should be kept in mind: 1. For general use the most suitable proportions of cement and aggregate are: 1 part of cement, 2 parts of sand and 4 parts of gravel. 2. Only fresh water free from organic matter should be used for reinforced work. Sea water is not allowed. 3. Homogeneity of the concrete is a very important requirement. Steel constructions with reinforced concrete have become the most important building materials invented in centuries and they have given modern architecture its peculiar features.
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