How to Make Cement

Since ages, humans have been using a binding material to make brick walls and firm structures to dwell in. Limestone was the earliest binder and the quest to obtain desirable characteristics, derived the cement, the ultimate binding material. It is a substance which not only sets fast but, also hardens as time passes. It also has most noteworthy quality of binding almost any material. The word 'cement' has a Roman descent. They described the structures made from crushed rock bound with burnt lime, by the term 'opus caementicium'. But, the procedure of making the modern-day cement involves using some state-of-the-art techniques.

The Process of Making Cement

As said earlier, the procedure of making cement is a complex one and is done using some latest technology. Here are the various chemical and thermal processes which are important to know:

Raw Material Mining
Limestone, sand and clay are three main raw materials required to make cement. They contain the four essential mineral elements required in making cement - calcium, silicon, aluminum and iron. Limestone and clay is mined from quarries by drilling or setting off explosions in to the rock. Large sized limestone rocks and boulders are fragmented in to smaller pieces and transported to the cement making plant using either huge dump trucks or high capacity conveyor belts.

Crushing
These medium-sized rocks now go through the first process in the plant. Here, they are first put in to heavy crushers which break down the rocks in marble sized pieces (approx 1½ inch in size).

Prehomogenization
This is a very important process of proportionally mixing the different raw materials. The limestone pieces are added to a blender where they are mixed with other raw materials in the exact required proportion.

Raw Material Milling
A vertical steel mill is made use of in this process which further grinds the blended material using the pressure exerted by three conical rollers. The rolling of these three rollers on the turning milling table crushes the blend in fine powder. Sometimes, horizontal crushing mills are also used in this process.

Calcination
This is the must-know core process, wherein, the crushed and blended raw material goes into a huge, extremely hot, rotating kiln to undergo a process called sintering. In this phase, the raw blend turns in to sort of partially molten state. The raw materials reach about 2700° F (1480°C) inside the furnace. This state facilitates some chemical and physical processes in the raw material. The resultant coming out of the furnace is small, dark gray, red-hot nodules called clinker, which are 1-2 inches in diameter.

Cement Milling
These clinkers are cooled and grounded into a fine gray powder. To extend the cement's setting time, small amount of gypsum is added during this process as this powder makes its way through the mill's two chambers. This is now the finished product and is called Portland cement or simply cement.

Packaging
Cement is stored in dry storage silos, from where it is extracted and packed in sacks on demand. It can be shipped by rail, road or ships, but extreme care is taken to maintain dryness.

Cement is one of the most important commodity today and its production and consumption is constantly on the rise. China is the largest manufacturer of cement in the world and accounts for about 45% of the world's cement. India and the US are distant 2nd and 3rd respectively with 6.5% and 4.5% of world's cement production respectively.

Cement manufacturing also has its environmental effects. The cement industry is responsible for emitting about 5% of the global CO₂ emissions. Nearly 900 kg of CO₂ is emitted for every 1000 kg of cement produced. The burning of fossil fuels produce other polluting gases as well.

The above-mentioned article enlists the most vital steps in making cement, which can be called a purely industrial process. After reaching the end, we can conclusively say 'don't try this at home'.