What is cement?
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| Cement |
Cement is an adhesive which is helpful to binding the sand and aggregates to produce concrete, that is the most versatile of building particle. Cement is prepared by blending calcium, silicon, aluminum, iron and other ingredients usually limestone, shale and clays in a thermochemical reaction to creates clinker, which is then ground to a fine powder for example microns and it mixed with ground gypsum and other additives to prepare cement. So, let's discuss about the Types of Cement.
Types of cement:-
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| Types of cement |
Thers are many different types of cement are available in recent days. So, let us consider the types of Cement one by one.
Portland Blast Furnace slag cement (PBFSC):
It is the one of the important types of the Cement. In this cement, the rate of hydration heat is found lower in comparison to PPC. It is mostly used in massive building projects. For example - Dams.
Sulphate Resisting Portland Cement:
This types of cement is applicable in the areas where concrete has an exposure to seacoast or sea water or soil or ground water. Under any such instances, the concrete is vulnerable to sulphates attack in maximum amounts and can cause spoil to the structure. Therefore, by using this sulphate resisting Portland cement one can lower the affect of damage to the structure. This cement has high scope in India.
Rapid Hardening Portland Cement:
The texture of Rapid Hardening Portland cement is quite similar to that of OPC. But, it is bit more fine than OPC and possesses immense compressible strength, that creates casting work simple.
Ordinary Portland Cement (OPC):
This type of cement is also known as grey cement or OPC. It is mainly use in ordinary concrete building. In the production of this type of cement in India, Iron (Fe2O3), Magnesium (MgO), Silica (SiO2), Alumina (AL2O3), and Sulphur trioxide (SO3) substances are useful.
Portland Pozolona Cement (PPC):
In PPC, the rate of hydration heat is lower. Fly ash, coal waste or burnt clay is used in the production of this category of cement. It can be available in low price in comparison to OPC. As it prevents cracks, it is helpfull in the casting work of huge volumes of concrete.
Oil Well Cement:
Oil well cement is made up of iron, coke, limestone and iron scrap. Oil Well Cement is used in building or fixing oil wells. This type of cement is applied on both the off-shore and on-shore of the wells.
Clinker Cement:
Clinker cement is produced at the temperature of about 1400°C to1450°C. Clinker cement is required in the building work of complexes, houses and bridges. The ingredients for this cement are - Iron, Quartz, Clay, Limestone and Bauxite.
White cement:
It is one of the type of Ordinary Portland Cement (POC). The substances used in this type of cement are inclusive of clinker, fuel oil and iron oxide. The content of iron oxide is maintained below about 0.4% to secure whiteness. White cement is highly used to enhance the aesthetic value of a construction. It is mainly used for tiles and flooring works. This cement prices more than grey cement.
What is the manufacturing process of cement?
There are three different processes are contained for the preparation of normal setting or Portland ordinary cement:
- Mixing of raw materials.
- Burning.
- Grinding.
1) MIXING OF RAW MATERIALS-
Now, In this process- the raw materials such as limestone or chalk and shale or clay may be mixed well either in dry conditioner or in wet condition. This process is usually called as the dry process and wet process of mixing.
- Dry Process:- Following is the flow chart of mixing of raw materials by dry process.
- Wet Process:- The flow chart of mixing of raw materials by wet process is shown in following figure-
2) BURNING-
Burning process is carried out in the rotary kiln which is shown in figure. It's having a length of 90 to 120 meters and a diameter of 2.5 to 3 meters. It is situated in a way that the kiln rotates 1 to 3 revolutions per minute. The corrected slurry is charged into the upper end of kiln. Coal in finely pulverized form, fuel oil and gas are the common fuels for burning these kilns. The part near the upper end is called as dry zone. Water of slurry evaporates in this zone.
When slurry descends to the next zone, the temperature rises and in next section Carbon dioxide from slurry is evaporated. Tiny lumps called nodules are produced at this step. These nodules passes through zones of maximum temperature and at the end reaches the burning zone where the temperature is around 1500°C.
At this zone nodules are transferred to small greenish blue balls which are called as clinkers .The clinkers are very hot almost 1000°C. When they coming out of the kiln. They are cooled and collected in containers of perfect sizes.
3) GRINDING-
The clinkers produced from the rotary kiln are grounded in tube mills. A minimum quantity of gypsum is also added to maintain the starting setting time of cement. Finally, the cement is fed to the packer machines.
What is the difference between the dry and wet processes of cement?
A) Dry process-
In dry process, all the materials in powder form are ground separated in the absence of water and after that mixed well in the suitable proportion and the resultant product is fed into kiln for burning.
This process results less consumption of energy. And low quality of product is achieved in this process.
B) Wet process-
The raw materials clay silica alumina is purified by washing with water and then mixed with crushed limestone to get raw slurry liquid which is then fed to kiln for burning. Energy comsumption is maximum in this process. Production of good quality product. Dust emission is low in this wet process.
Uses of cement-
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| Uses of cement |
1. Cement is a binding material, therefore obviously it is used to bind materials and enhance the strength.
2. It can be used to fill cracks formed.
3. It can be used to build buildings or for many other construction.
4. Now, the used cement are being crushed and been used again in form of aggregate.
What is the difference between opc and ppc cement?
OPC actually means Ordinary Portland Cement. OPC is standard concrete used for many different purposes.
PPC mean Pozzolanic Portland CementPozzolans are siliceous substance that can be mixed to concrete mixtures, potentially lower the mix cost without toxic the performance characteristics. In some cases pozzolans will actually enhance a concrete's resistance to chemical intrusion. This rises the concrete's performance when subjected to chlorides or sulfates. Pozzolans may slow the curing rate of the concrete, resulting in low break strengths at early tests, such as a one day test, when compared to Ordinary Portland Cement. In the long term, PPC cements typically achieve strengths equal to or greater than OPC.
As with most things, the real answer depends on the specific use and location. Not all types of concrete are available in all spaces or areas, and the prices may vary. If the pozzolanic material is not available, or has to be shipped from a distant location, while the portland cement is produced locally, OPC concrete may be non-expensive than PPC.