Cement is manufactured by the combination of calcium, silicon, aluminium, iron and other ingredients.
Other common materials used to manufacture cement include limestone, shells, and chalk or marl combined with shale, clay, slate, blast furnace slag, silica sand, and iron ore. The process is these ingredients are heated at high temperatures to form a rock-like substance. Then it’s ground into the fine powder as cement.
Bricklayer Joseph Aspdin of Leeds, England first made Portland cement early in the 19th century by burning powdered limestone and clay in his kitchen stove.
Cement industries check each and every step while manufacturing Portland cement. They do frequent chemical and physical tests to comply with all industry specifications.
There are many methods used to manufacture Portland cement. The most common way to is through a dry method. The first step is to quarry the raw materials such as limestone, clay etc. After quarrying the rock is crushed. The first crushing reduces the rock to a maximum size of about 6 inches. Then it goes to secondary crushers for reduction to about 3 inches or maybe smaller.
The crushed rock is combined with other ingredients such as iron ore or fly ash and ground, mixed, thus cement kiln is prepared.
The cement kiln heats all the ingredients to about 2,700 degrees Fahrenheit. It is a huge cylindrical steel rotary kilns lined with special firebrick. Kilns may be as much as 12 feet in diameter. They are large enough to accommodate an automobile and longer in many instances than the height of a 40-story building.
The finely ground raw material or the slurry is fed into the higher end. At the lower end is a roaring blast of flame, produced by precisely controlled burning of powdered coal, oil, alternative fuels, or gas
After the clinker is cooled, cement plants grind it and mix it with small amounts of gypsum and limestone. Cement is so fine that 1 pound of cement contains 150 billion grains. The cement is now ready for transport to companies to be used in a variety of construction projects.