What is cement? What does it do? How is it made?

Most people know what cement is, after all it is widely used in the modern world. What most people may not know however is just how long it has been used as a construction material or how it is made. Cement is one of the oldest building materials and it will likely play an increasingly important role in the future, especially as it becomes more and more necessary to find replacements for wood.

The definition of cement is that it is a fine grained powder that when it is mixed with water turns into a solid. Because of its strength cement is widely used for construction projects. There is a lot of confusion about just what the difference is between cement and concrete. Basically concrete is what you get when you mix cement with an aggregate like gravel or sand. You can think of concrete as being the actual building material with the cement being what holds it together. That being said the two terms are frequently used interchangeably even though it is actually incorrect.

The basis of cement is lime; it has been use a binding material in construction for thousands of years. In the past lime was simply heated by itself in order to drive out the carbon dioxide and leave calcium oxide which is what was used to make cement. These days they use what is called Portland cement. This is made by heating lime and clay together. They then crush it and add gypsum to the mixture. The gypsum will slow down the rate at which the cement hardens making it easier to use.

Cement is widely used in the construction industry. Your house almost certainly has a foundation that is made of concrete. We are even starting to see whole houses that are being built out of concrete. In addition most sky scrapers are made largely of concrete as well. Everything from sidewalks to bridges are made using cement it is one of the most widely used building materials that there is. The widespread use of concrete for building is fairly new and has really only become possible as a result of the development of pre-stressed concrete.

The reason that cement has only recently become widespread in construction is that by itself it is not all that strong. It is very strong under compression, that is it can hold a lot of weight sitting on top of it. However cement is not all that strong when it comes to supporting its own weight. This is why when you see construction work being done with cement you almost always see rebar being put down before the cement is poured. This makes the cement much stronger and far more practical as a construction material. It also makes it much easier to build using cement.