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Cement is a mixture of calcium, silica, aluminum, and iron. Calcium is the primary ingredient in cement-making and is obtained from limestone found in a quarry. Silicon is usually obtained from sand and clay, and aluminum and iron are extracted from bauxite and iron ore. These four ingredients are mixed together and heated up in a high-temperature kiln. This extreme heating actually transforms the physical and chemical composition of the materials into a material called clinker—a gray pebble-like substance.[1]

Clinker and gypsum are then crushed down together inside a crusher to form a fine powder. This is how cement is made. Gypsum, in dry wall and plasterboard, is a chalky white substance. This whiteness of gypsum is what gives cement its light gray color. There is a version of cement called white cement but it is typically more expensive.[2]

Powered cement is then mixed with water and aggregates to make concrete. It is the formation of clinker through the heating of calcium, silica, aluminum, and iron to a high temperature that gives cement its binding property. This is important since cement is used widely in construction applications and serves as the primary bonding ingredient in concrete.[3] In fact, concrete is the second most prevalent consumable in the world today next to water and is used twice as much as any other type of building material, including wood.

Cement as a product is widely adaptable and when mixed with certain variants make different cement products.

  • Sand, gravel, and water mixed with cement form concrete
  • Water and sand mixed with cement form cement plaster
  • Water, sand, and lime mixed with cement form mortar

[edit] Process

Producing cement is a lengthy process that involves multiple steps. Limestone, the primary ingredient in making cement, has to be gathered from a quarry to a cement-making plant where it is fed into a crusher and broken down into more manageable marble-sized pieces. The limestone then has to go into a blender-type machine that mixes in just the right proportion with the other remaining raw materials. These ingredients are ground into a powder, sometimes with an apparatus that has rollers and crushes the powder against a rotating platform.

The next step in making cement is called sintering. Sintering essentially means causing something to become a coherent mass by heating, not melting. In the case of cement, the powder is heated to a very high temperature of up to 2,700 degrees Fahrenheit inside a furnace to the point it is partly molten. The heating causes a chemical and physical reaction and the mixture emerges from the kiln as large, glassy red-hot cinders, or clinkers. Once cooled down, the clinker can be crushed again into power, mixed with gypsum, and reground again to form portland cement.[4]

[edit] References

  1. About Cement. Cement Org. 2008-10-07.
  2. Cement. Buildeazy. 2008-10-07.
  3. About Cement. 2008-10-07.
  4. Cement. Buildeazy. 2008-10-07.