In the simplest form of the word, cement is a binder. It is a substance that sets and hardens independently. It can also bind other materials together. Tracing back to the roots of the word, “cement” was used by Romans who dubbed it “opus caementicium”. This was to describe masonry that resembled concrete and was made from crushed rock with burnt lime as binder. Later on, the volcanic ash and the pulverized brick additives were added to the burnt lime to obtain a hydraulic binder. This was known as cementum, cimentum, cament and cement. In construction, cement is characterized as hydraulic and non-hydraulic. There are other cement products which are used today.
The production of mortar and concrete is the most important use of cement. The bonding of natural or artificial aggregates forms a strong building material that is durable in the face of normal environmental effects.
However, the term concrete should not be confused with the term cement. For cement refers only to the dry powder substance used to bind the aggregate materials of concrete. With the addition of water and/or additives, the cement mixture is formed that is referred to as concrete, especially when aggregates have been added.
The Early Uses of Cement
It cannot be said for sure when the combination of hydrated non-hydraulic lime and pozzolan produced a hydraulic mixture, had been discovered. Roman engineers where the first to use the concrete made from large scale. Natural pozzolans and artificial pozzolans had been both used in these concretes. Some of the structures that were built from these concretes sich as the huge monolithic dome of the Pantheon in Rome and the Baths of Caracalla are still standing to this day. There was extensive use of hydraulic cement in the vast system of Roman aqueducts as well. In medieval Europe, however, the use of structural concrete vanished. Nevertheless, weak pozzolanic concretes were used as a core fill in stone walls and columns.
The Modern Cement
In the modern world, there are many cement factories and cement manufacturers. An important contribution was made by John Smeaton for the development of cements when he was making the plans for the construction of the third Eddystone Lighthouse in the English Channel. A hydraulic mortar was needed that was set up and developed some strength in the 12-hour period, between successive high tides. He took an extensive market research on the available hydraulic limes, visiting their production sites and noted that the “hydraulicity” of the lime was directly in relation to the clay content of the limestone from which it was made. Smeaton was a civil engineer by profession however he did not take the idea further. However, in the 19th century the same principle was identified by Louis Vicat in the first decade. He was not aware of Smeaton’s theories. It was not until 1824 that Joseph Aspdin found something that we know now as Portland cement. It was dubbed thus because of render which was made from it was in the similar hue to that of the prestigious Portland stone.
Even in this day, Portland cement is what is widely used by all construction workers. Of course, for plastering gypsum plaster is preferred over plaster of paris.
Author Bio: Chandana Goyel in this article explores how simply we can talk to kids about cement and construction.