Cement is an industrial material produced by heating a mixture of grinded limestone and clay in special kilns at temperatures of around 1,450oC. The product resulting in these conditions from the transformation of the raw materials is called clinker and is then grind into powder to become the cement.
Source: orykta.gr
The use of cement has quite a long history. The oldest concrete known today, dating from 7,000 BC, is found where Israel is now located. It consists of a mixture of lime with stones and formed a floor. It is remarkable that in both cases of the great pyramid of Egypt and the construction of the Great Wall of China, cement-like materials were used.
This building technique was also adapted by ancient Greeks, who used various lime mixtures for building and for coating bricks made by clay and dried in the sun. Ancient Greeks were probably the first to use hydraulic mortars, that is mortars which when mixed with water, can set and harden in the air, as well as into the water, thus achieving a significantly higher resilience to environmental effects over time.
During the 1st century AD, Romans refined this “binding material”. By adding a volcanic material from the Pozzuoli area, near Naples, they discovered that they could achieve this mixture coagulation under water.
However, the English engineer John Smeaton is credited for making the first substantial step to create cement in the form that is used today. In the mid-1,700s AD, he succeeded in creating the first contemporary concrete, by mixing pebbles and ground bricks (as aggregate) with hydraulic mortar. A few years later, in 1824, the English inventor Joseph Aspdin, invented Portland Cement, which is the dominant form of cement used in concrete production until nowdays.
Reinforced concrete was created in 1849 by Joseph Monier. It combines the tensile and bending strength of steel and the compressive strength of concrete, in order to withstand heavy loads, consequently allowing it to be used in buildings, bridges and other structures.
The beginning of the 20th century is marked by two significant innovations in cement production:
a) the production of white cement by replacing clay with kaolin, and
b) the discovery of Ciment Fondu® by Jules Bied in 1908, a cement manufactured from a mix of limestone and bauxite that exhibits resistance to extreme environmental conditions and high temperatures.
The cement production process is illustrated in the figure below:
Concrete or beton by mixing cement with sand, gravel and water.
Reinforced concrete or béton armé by the combination of steel (in the form of circular bars or mesh) and concrete.
Cement mortar resulting from mixing cement with sand and water.
Binding materials (glues) from mixing cement with fine aggregates.
Other building materials such as concrete blocks, pipes, prefabricated elements, etc.
