Современные проблемы промышленного и гражданского строительства на занятиях английского языка. Кузьмина Е.В. - 28 стр.

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UNIT 5

TEXT A. FROM THE HISTORY OF CONCRETE.

Mass or plain concrete dates from very early days. It was employed by

the Egyptians, Romans and Greeks in the construction of aqueducts and

bridges, in the construction of roads and town walls. Romans used it even in

under-water structures some of which have survived till our time. A large part

of the Great Chinese Wall (the 3

century before our era) was also built of

concrete.

The concrete remains of the foundations of buildings built several

thousand years ago have been found in Mexico. As cement was not known in

those times, concrete was made of clay and later of gypsum and lime.

Nowadays concrete is made, in up-to date machinery with very careful

regulation of the proportion of the mix.

The idea of strengthening concrete by a network of small iron rods was

developed on the 19

century, and ferro-concrete was introduced into

engineering practice.

Text B. Concrete.

It is difficult to imagine modern structure without concrete. Concrete is

the very building material which led to great structural innovations. The most

important quality of concrete is its property to be formed into large and strong

monolithic units. The basic materials for making concrete are cement, aggregate

and water. Cement is the most essential material and the most important one for

making concrete of high quality. Cement is made of limestone and clay. It is

burnt (calcined) at high temperature and ground up into powder. Depending on

the kind and composition of the raw materials different types of cement are

obtained. Portland cement, blast furnace cement is suitable for putting up

marine structures.

Concrete is made by mixing cement, water, sand and gravel in the right

amount. As soon as it is thoroughly mixed it is poured into forms that hold it in

place until it hardens. The crystals forming in the process of making concrete

stick together in a very hard artificial stone. Cement starts hardening one hour