Info about Cement
Cement
Cement is a substance that is used to hold material together. The term comes from the Romans who used the term opus caementicium in reference to a masonry material that was made from ground rock and a burnt lime binder. They added ash from volcanoes and crushed brink to get a hydraulic binder that later became known as cement.
There are two types of cement. One is called hydraulic because is hardens from a chemical reaction to water. It can harden anywhere including underneath the water. It is not affected at all by we weather. The other kind is called non hydraulic cement like gypsum, lime, and plaster have to be kept dry if they are to gain strength.
The chief use of cement is to produce concrete and mortar. You must not confuse concrete with cement. Cement only means the dry powder substance that is used to bind materials together. It is only when water is added that it becomes known as a mixture called concrete.
It is not clear where it was discovered that cement used with other binding elements created a hydraulic mixture. However, it was the Romans who first used concrete made from a mixture on a very large scale. There are many of the structures that they built with this still standing today. They used it to build the Pantheon, large baths, and the extensive Roman acqueduct system. Structural concrete use was not found in medieval Europe although they still used weak mixtures of crushed brick and rock to fill the stone walls and columns.
The Industrial Revolution brought about the development of modern cement. It was developed for finishing brick buildings when the climate was wet, construction in harbors that came in contact with ocean water, and making strong concretes.
Britain had especially goo building stone the became increasily expensive and it was common for new prestigious buildings to be constructed from the new insustrial brick and finished with stucco so they would look like stone. They preferred to use hydraulic lime cement for these buildings but they needed something that hardened fast. This brought about the development of new cement. Roman cement, developed by James Parker around 1780, became the most popular. It was really nothing at all like the materials used by the Romans. Instead, it was a natural cement that was made from clay mineral and calcium carbonate. It was ground up into a very fine powder. This was mixed with sand to become a very quick set mortar. It would set in around fifteen minutes time.
The quick set time became a problem because it did not allow enough time to get the bricks placed before it hardened. This early cement also took many weeks to gain strength before other building materials could be placed on it.
Through much experimentation they learned to heat limestone and add other materials like clay and cook it in a kiln. The process became known as calcination because a carbon dioxid molecule is released from calcium carbonate to form calcium oxide. This process was gradually perfected until it became the product that we know Today as Portland Cement.