For the production of cement, the first stage is the mining of its basic ingredients which are limestone, marl, and clay in quarries. There are various ways to extract the raw materials such as digging or blasting. Once these raw materials are collected, the next step that follows would be to crush them into smaller pieces. This mailing process includes the addition of minerals that are required to ensure the correct chemical composition for the final cement product. The fine powder-like result from the milling process is then sent to the kiln where it would be heated at temperatures around 1500°C. At these high temperatures, the raw meal converts into smaller granules that have gone through chemical reactions and are called clinkers.
Once the clinker is done, it is stored to cool down and get ready for the next stage where it would be mixed with gypsum. Around 3 to 5 percent gypsum is added to the clinker to regulate the setting of the cement. Once the addition is done, it is finely grounded and other applicable additions are added to the mix. Each of these additions carries some properties that can give specific features to the cement such as easier workability, high-quality finish, reduced permeability, and so on. After the completion of this stage, the final product called cement is ready to be shipped. They are stored in silos which are then distributed to various plants and dealers
Cement is a versatile construction material that has significantly contributed to the industrialization and urbanization of our current society. Being an essential part of the whole construction process, it has diversified into different types which are used depending on their specific features and environmental needs. Some of the most common types of cement available in India are as follows:
Ordinary Portland cement (OPC) 53 grade is suitable for a wide variety of civil construction. It successfully passes the criteria of IS:12269-1987 Grade. This type of cement is known for its high strength and durability. It has the right particle size distribution and good crystallized structure which benefits the stability of the mixture. As it is high-strength cement, it is popularly used in the construction of bridges, chimneys, concrete roads, skyscrapers, and other heavy load-bearing structures. Compared to any other type of cement, OPC 53 grade is superior for its early strength. It does not increase a lot after 28 days. With the help of good supervision and controlled quality assurance measures, the risks of micro-cracks due to higher heat of hydration can be avoided.
Ordinary Portland Cement 43 Grade refers to the type of cement which is expected to have comprehensive strength of 43 MPa in a cube cast by 28 days. It passes the requirement of IS:8112. Being slightly different from OPC 53 grade cement, this type of cement would continue to gain strength after 28 days as well. Though It should be noted dark the ultimate strength for both OPC 53 and 43-grade blocks of cement would be the same. With OPC 43 grade cement, that would be medium heat of hydration. As this type of cement does not rapidly harden, it is used for construction purposes like plastering or flooring. It is also popularly used in the manufacturing of precast items such as pipes, blocks, tiles, etc.
Portland Pozzolana Cement (PPC) is made by using pozzolanic materials which are siliceous and aluminous. These materials do not have cementitious properties on their own but when they come in presence of moisture and are chemically reacted with calcium hydroxide at ordinary temperature, they can form compounds that would have cementitious properties. Common types of pozzolanic materials may include calcined clay, volcanic ash, silica fumes, or fly ash. PPC material is widely used in plaster and brickwork, Marine work, mass concrete work, and RCC work in residential and construction buildings. As this material has less permeability of water, it is highly durable for concrete structures. It also has higher resistance against sulfates, alkalis, chlorides, or chemicals. They have a low heat of hydration and are easier to work with. Also, it should be noted that PPC is popularly used to achieve a smooth surface finish.
Now that we have a clear understanding of how cement is manufactured and what are types that we can use to achieve our applications, it is time that we understand how Cement price works. Here are some of the top factors that influence the pricing for blocks of cement.
As discussed above, there are different types of cement grades that come with specific features and IS code satisfaction. To give you a quick example, OPC 53 grade cement would have a higher price tag than the 43-grade cement. This is because OPC 53 grade has higher durability and is used extensively for high load-bearing structures. Depending on the grade of the cement, their pricing structure would differ and the higher the cement grade is, the costlier it would be. Even among the same grade of cement, the prices of the product can be slightly more for different quality categories. For example, the price tag of OPC 53 grade from a reputed cement brand would be more than the cement price in Lucknow from a local cement producer. Higher quality cement would require high-quality raw materials which makes the prices soar.
As explained in the process of cement production, having a fine texture is important for cement products. Good quality cement would go through various stages to convert into very fine particles. Any type of cement that has lumps in it, clearly shows that it has been produced with low quality and would not offer good quality finish in the construction work. These low-quality cements might have a lower price tag but it is not advised to invest in them as they will ultimately cost you heavily due to the likely damages.
This one might seem obvious as heavier sizes of product proportions would cost more than their smaller counterparts. Depending on your purpose, you can buy 50 kg cement bags which would be sufficient for your task. Cement from reputed cement manufacturers would always have the correct weight with each product. It is highly advised that you check the sample weights before purchasing them. When you are paying for a certain amount of weight, you must receive the same in the best condition and good quality.
Any type of cement which is older than 15 days is not advisable for purchase. The cement hardens when it comes in contact with moisture or air. This is why cement which is older than 15 days has most probably reacted and is no longer good for construction work. While making your purchase, you must ensure that the manufacturing date is within the 15 days range. Some sellers might try to sell old cement at discounted prices. Beware of such schemes and always ensure the correct manufacturing date before you purchase it.
To ensure that the cement complies with the quality standards required, they are meant to go through certain tests. When you are purchasing cement, ensuring their genuineness and test completion is important. Similar to a proper test certificate for the cement product, you should also ensure that a proper invoice is given for the product. As it is possible that scam sellers would try to rip off customers with ungenuine products in the name of branded cement manufacturers. Always make a point to get a proper invoice and bills for your purchase.
Following tests can help you establish the quality of the cement you are using:
Using a sieve test or air permeability test, we can determine how fine the particles of the cement are. For a good rate of hydration and proper chemical reactions, the particles must be very fine in size.
How long the cement takes to set is also an important parameter for its overall quality. For testing this, a needle is penetrated the cement paste, and the time taken by it to penetrate 33-35 mm of depth into the paste shows the initial setting time. Once the paste hardens, the time taken to penetrate not more than 0.5 mm is recorded as the final setting time.
This test proves how consistent the cement paste is with its water content. Good consistency is important for the overall stable and durable quality of the mixture. This test is usually conducted with the help of Vicat's apparatus which includes a plunger of 10 mm diameter and 50 mm length. This would penetrate for depths of 33 to 35 mm in 3 to 5 minutes of mixing.
The average strength for cement needs to be measured to check its durability and heavy load-bearing capacity. In this test, a cement mortar bracket is used in the tensile testing machine. A mixture of 1:3 cement and sand mortar with 8% water content is cured for 24 hours at 25°C in a space with 90% relative humidity. This process is carried on to find average strength after 3 and 7 days of testing.
Now good quality cement can be availed at a good cement price in Lucknow. By following the above-mentioned tips, you can also enjoy the best possible quality of cement for various construction purposes. From residential household renovations to heavy-load structures, the use of cement is prevalent everywhere. Finding good quality cement can become the key to sustainable structures that would last long and serve their purpose with durability. It should be noted that the quality of the cement is never advised as it is the key ingredient in all construction purposes.