With 2 billion tons being produced throughout the world each year, cement is the most widely used material in the world and its use impacts every aspect of daily life. It has a surprisingly long history as well, with the ancient Romans using it for their infrastructure and even such well-known structures as the Colosseum. Despite its widespread use and how commonplace it is, what exactly is cement processing and how is it made?
At its very basic level, cement is a binder that is mixed with water to create a paste which is used to adhere and harden with other materials, binding the materials together. When cement is mixed with a coarse aggregate such as rocks, it is called concrete. Cement is usually manufactured from limestone, shells, or chalk and mixed with various other ingredients to give it unique properties, such as shale, clay, silica sand, coal fly ash, or iron ore.
The most commonly used way to create cement is to gather the raw materials by mining out of a quarry, and then crushing the rocks several times. The crushed rocks are mixed with the other ingredients and fed into a kiln where it is heated to 2,700 degrees fahrenheit, where certain elements are burned off as gases, and the elements that are left over combine into a product called clinker, which are marble sized balls of hardened materials.
The red hot balls of clinker are discharged out of the kiln into coolers until they are at a safer temperature, and then these cooled pieces of clinker are ground into a fine powder and mixed with gypsum and limestone. The cement is then ready to be used or mixed with an aggregate to create concrete, and is packaged for shipping.