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Cement History in the World

Cement History in the World:


Using cement materials has ben popular since a very long time ago. Egyptians used gross Calcined gypsum; Greeks and Romans used Calcined limestone and later learned to add sand, crushed stone, bricks and broken pottery to a mixture of quicklime and water. This was the first type of concrete in the history.
Quicklime mortar does not harden under water and Romans grinded stone, quicklime, volcanic ash and very soft powder of burnt pottery and used them in underwater construction.  The active silica and alumina in the ash and pottery mixed together and produced a kind of cement called Pozzolana cement (its name is taken from Pozzuoli, the name of a village near Mount Vesuvius where they found volcano ash for the first time). The name, Pozzolana cement, has been used to describe the cements which are easily produced by grinding natural material at room temperature. Some of the Roman building like Coliseum in Rome, Pont du Gard near Nimes, concrete structures like Pantheon building in Rome in which the bricks were stuck by mortars remained so far and their cement materials are sill hard and solid. In the ruins near Pompeii the sticking mortar are mostly less weathered than the stuck stones, which are fairly weak.  In the Middle Ages, there was a decline in the quality and use of cement but in the 18th century the knowledge of cements progressed.  In 1756, JohnSmeaton who was responsible for reconstructing the Eddystone beacon tower at Englandsouthwest offshore came to the conclusion that the best mortar is made when the pozzolanic materials are mixed with the limestone containing a remarkable amount of clay. By determining the role of clay, which was considered inappropriate before that, Smeaton was the first person who recognized the chemical characteristics of Hydraulic lime which is made up of heating a mixture of stone and clay. Consequently other types of hydraulic cements were produced like the Roman Cement which Jomes Parker created by clacininglumps of clay lime stone. Eventually in 1824 Joseph Aspdin, a British bricklayer from Leeds recorded Portland cement. He produced it by heating a mixture of soft powder of clay and limestone in a kiln to the point that it’s CO2 was sent out; the temperature of the kiln was so much less than the necessary heat for making clinker. 
The first instance of the cement which today is called Portland cement was made by Isaac Johnson in 1845. He produced it by heating a mixture of clay and limestone to make clinker and to perform necessary reactions for producing strong sticky compounds. 
It was initially named “Portland cement”because of its similarity in color and quality with Portland stone which was a limestone in Dorset in England. Since then the name is used all over the world to refer to the cement which is produced by mixing and heating clay and lime materials or others containing silica, alumina and iron oxide to point of becoming clinker and grinding the produced clinker. The definition of Portland cement in different standards based on this procedure whether gypsum is added to it after heating or not. Today other materials my also be added.  

Constituents of Portland cement:

We should consider the fact that the most popular type of cement used in construction industry including bridges, tunnels, roads or building has always been Portland cement. The materials which are heated in the kiln to produce cement are made up of two main materials: clay and limestone. And if we study the materials distinctly, they are  1- lime  2- silica  3- Aluminum Oxide  4- Magnesium oxide  5- other materials. 
We should also have in mind that the mentioned constituents are put in the kiln in different amounts which are determined by the type of the cement and its other technical characteristics. Sometimes a natural mixture of clay and limestone with the needed amounts in are found exactly in the nature which are called MARL. If all constituents are not found in the clay we could add them to it. These materials are predominantly obtained from the industrial waste of factories. 

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