Popular as a binding material, cement is a very important building material. Almost all construction work needs cement. So, the cement composition and the manufacturing process are quite important to understand.
Why is it important? By understanding what cement is made up of, it is easier to understand how it works, why it has its particular properties, and how different types of cement are made.
Cement is a finely powdered substance made from a mixture of elements that are found in natural materials such as limestone, clay, and sand. Limestone is the major raw material used to make cement, usually mined from the quarry, and it is crushed into a powder. The main element found in limestone is calcium carbonate, which makes up around 80% of the cement.
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 the composition of cement are shells, mark, limestone, chalk, silica sand, and/or blast furnace sand. The most common way to manufacture cement is through the dry method where a powdery substance is created from a combination of raw materials.
In England, a bricklayer named 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 through 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 the 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 a 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 is mixed, ground, and fed to a cement kiln.
Once it’s in the cement kiln, the kiln then heats up all the ingredients to around 2700 degrees Fahrenheit, which is hot enough to fuse the components together. After that, the molten material goes through a cooling rotary kiln and forms what we call clinker, a grayish-black substance.
Gypsum is added during the grinding process as an additive to control the setting time of the cement mix. After that, it is ready for packaging or shipping.
What are the Components Of Cement
Although some cement mixtures may vary, here’s the general percentage of cement ingredients that are commonly used:
- 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%
Cement Ingredients and Their Functions
Each ingredient of cement has a specific purpose, allowing it to work together with other ingredients to give properties such as strength, setting time, and feel. Here is a quick description of each ingredient:
Lime is calcium hydroxide or calcium oxide. The presence of lime is needed to form calcium aluminates and silicates. These components give strength and also improve the setting time of cement.
Lime deficiency decreases the strength of the property and causes the cement to set faster. Excess lime makes cement unsound and causes the 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 which must not be present more than about 2% in cement. Excess magnesia decreases cement strength.
- Iron Oxide: It imparts color to cement that also acts as a flux.
- Calcium Sulfate: Its chemical formula is CaSO4 which 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.
What is Cement Made Of: Final Thoughts
Being one of the main ingredients in modern construction, cement is highly important in the world today. It’s made up of several ingredients to which certain proportions are added and then processed through a complex manufacturing process.
The end result is a binding material that can be used as mortar or concrete for various processes in construction. Both manual and machine labor play an integral part in the making of cement and the many ingredients that make it up. Without it, modern construction would not be possible.