Popular as a binding material, cement is a very important building material. Almost all construction work needs cement. So, the cement composition is a matter of interest to engineers.
One must know about cement and its ingredients functionality for understanding the composition of cement. Hence, here is a guide on what cement is, how it is made, and its components.
What Is Cement?
Cement is the fine gray powder mixed with water and other substances to make concrete or mortar. It is a crucial building material in both commercial and residential construction work. Cement is essential because it holds or binds the cement mix together by giving strength.
How Is It Made?
Cement is made via a closely controlled chemical combination of aluminum, silicon, calcium, iron, and other ingredients. Some common materials helpful in manufacturing cement involve chalk, limestone, shells, or marl having combination with blast furnace slag, iron ore, clay, slate, and silica; when you heat these ingredients at high temperatures it form a rock-like substance which is later grounded into fine powder commonly considered as cement.
In England, bricklayer Joseph Aspdin Of Leeds made cement earlier in the nineteenth century by burning limestone powder and clay in the kitchen stove. He lays the foundation for the industry that processes literally mountains of cement rock, limestone, clay, and other materials in a powder annually.
Laboratories of cement plants check every step in the manufacturing process of cement by frequent physical and chemical tests. Labs also test and analyze the end product to ensure that it complies with all industry specifications.
The most common way of manufacturing cement is a dry method. The foremost step is to quarry the primary raw materials, clay, limestone, and other materials.
Rock is crushed after quarrying the stone as it includes few stages. First, crushing decreases the rock to the largest size of 6 inches. Next, the rock goes to hammer mills or secondary crushers to reduce around 3 inches or smaller.
Crushed rock has a combination with other ingredients like fly ash or iron ore and mixed, grinded, and fed to a cement kiln.
Cement kiln heats up all ingredients to around 2700 degrees Fahrenheit in vast cylindrical rotary kilns lined up with special firebrick. Kilns are frequently about 12 feet in diameter larger for accommodating the automobile in many instances than the height of a 40 story building. Large kilns mount with an axis inclined slightly more than horizontal.
The fine ground raw material or slurry is fed at a higher end. At the low back is a roar flame blast manufactured by controlled burning of powdered coal, fuels, oil, or gas precisely under forced draft. The remaining elements unite to form a new substance known as clinker. Clinker comes out of kiln-like grey balls around marble size.
Clinker is discharged red-hot from the low end of the kiln, which is purchased down for handling temperatures in different types of coolers.
The hot air from coolers is returned to kilns, which saves fuel and gains burning efficiency. After cooling the clinker, cement plants mix it and grind it with small portions of limestone and gypsum.
Cement is fine, so that one pound of cement consists of 150 billion grains. Cement gets ready to be transported to get used in a variety of construction projects.
Components Of Cement
The general percentage of these Cement ingredients is as follows –
- Lime – 60 to 65%
- Alumina – 3 to 8%
- Iron Oxide – 0.5 to 6%
- Silica – 17 to 25%
- Sulfur Trioxide – 1 to 3%
- Magnesia – 1 to 3%
- Alkaline – 0 to 1 %
- Calcium sulfate – 0.1 to 0.5%
Some functions of cement ingredients are –
The main features of ingredients of cement, along with their usefulness or functions, are given below-
Lime is calcium hydroxide or calcium oxide. The presence of lime is needed to form calcium aluminates and silicates. Lime deficiency decreases the strength of the property and causes the cement to set faster. Excess lime makes cement unsound and causes cement to disintegrate and expand.
Silica is silicon dioxide that needs to be present in cement for tricalcium and dicalcium silicate. Silica provides strength to cement that presents to the extent of around 30% cement.
Other elements include –
- Alumina: Alumina is known as an aluminum oxide that imparts faster setting properties to cement.
- Magnesia: It is known as magnesium oxide that must not be present more than about 2% in cement. Excess magnesia decreases the cement strength.
- Iron Oxide: It imparts color to cement that also acts as a flux.
- Calcium Sulfate: Its chemical formula is CaSO4 that is present in cement in gypsum form. It may retard or slow down the setting of cement.
- Sulfur Trioxide: It must not be present more than 2%, and an excess amount of it may cause the cement to be unsound.
- Alkaline: Alkaline must not be present more than 1%, and excess of it may cause efflorescence.
Thus, all components of cement must be present in appropriate portions.
Cement is helpful as the main element in building construction. With the help of cement, concrete can be prepared. Also, there are many applications of cement.