Cement

Today, cement is indispensable in the construction. It is the main component of concrete solution. Without cement not get solid building blocks, not to build any bridge or building, no stadium, no airport. A particularly important property of the cement is hardening in water. Even in ancient times to make lime ability to harden in water was added thereto natural volcanic product puzzolana or artificial a brick dust. All these materials contain in their composition of oxides: silicon dioxide, SiO2 (silica or silicic acid), aluminum oxide Al2O3 (alumina) iron oxide Fe2O3. These materials cause interactions with them lime. Thus there is addition of water (hydration) to form a first silica compounds. The resulting insoluble calcium hydrosilicates crystallize. In the Middle Ages it was accidentally discovered that limestone products firing the contaminated clay by water resistance are not inferior to the Roman pozzolanic mixtures and even surpass them.

Today, cement is indispensable in the construction. It is the main component of concrete solution

It turns out for produce cement to need furnace slag, which previously never been used and simply discarded. For this purpose, the molten slag is mixed with red clay or milled slag with clay. Due to complex reactions between silicate slag and kaolin clay obtained complex calcium alumino-silicates - cement.

In 1824, D. Aspdin received a patent in England for the manufacture of cement from lime dust mixed with clay and baked at high temperature. Thus obtained spongy gray material called clinker, it breaks down and mixed with water. When solidification formed very durable building stone, which inventor called the Portland cement, because the color and strength, it looked like a building stone mined in the English city of Portland. Name of cement remained.

In the late 20th century, the number of varieties of cement was about 30. On the strength of the cement is divided into brands that are determined mainly by a compressive strength of samples, prisms halves the size of 40*40*160 mm, made of cement solution of 1:3 with quartz sand. Stamps are expressed in numbers M100 - M600 designating the compressive strength, respectively, in the 100-600 kg/cm2 (10-60 MPa).

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