What Cement is Made of: Its Composition and Properties

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Cement is regarded as one of the greatest inventions in history. Without cement, the tall buildings and the highly decorated homes and establishments we see today wouldn’t be possible to construct. Most of the things found indoors and outdoors, from walls and floors to bridges and roads, are made of cement, which is why it is also considered one of the inventions that sparked modernity in the world.

While cement is used in almost everything today, not all people actually know what cement is made of and how it is manufactured by cement suppliers. So, how is cement made? And what are the raw materials used for creating cement? We will find out more as we take a look at the intricacies of cement and its properties.

How and What is Cement Made From?

Cement is a substance that hardens and binds with other materials to create a solid object. This binding substance is mostly used to create walls and flooring for buildings, houses, bridges, and roads. Because of the abundance of cement in most countries around the world, the substance is the Earth’s second most-consumed resource after water.

When cement is mixed with sand and gravel, it produces concrete. In addition, when it is mixed with fine aggregate, which are natural sand particles collected from the mined lands, the cement can produce mortar, a type of paste that is usually utilized for masonry.

In terms of what cement is made of, it usually consists of raw materials like limestone and gypsum. Those materials would then be utilized to create two types of cement that are based on how they harden and adhere to other materials, and these are non-hydraulic cement and hydraulic cement. Here are details about those two cement types.

Non-Hydraulic Cement

Non-hydraulic cement is made of lime, oxychloride, and gypsum plaster, and it hardens without the need to mix it with water. The hardening process of non-hydraulic cement occurs when it is exposed to carbon dioxide, which is a kind of gas that is naturally present in the Earth’s air. So, when you pour the non-hydraulic cement out of its container, it will automatically be exposed to carbon dioxide and will already harden in a few hours.

In order for non-hydraulic cement to retain its strength and durability, it must be kept dry at all times. So, this type of cement may not be suitable for countries or areas where rain often occurs. Another downside of non-hydraulic cement is that it would take longer for the substance to harden compared to hydraulic cement, which has a faster hardening and adhering time.

Hydraulic Cement

Hydraulic cement is made of limestone, gypsum, and clay, and this substance hardens when it is exposed to water. Even if it’s submerged in water, hydraulic cement can still harden and adhere to other materials to form concrete or mortar.

As previously stated, hydraulic cement also hardens faster than non-hydraulic cement, which is why more contractors or companies are using hydraulic cement since it can help in building buildings, homes, or roads faster. Hydraulic cement is very advantageous in countries or areas where it is always raining, as the people that use this type of cement don’t have to worry about the rain since it mostly wouldn’t affect the quality or strength of the cement.

What are the Raw Materials for Making Cement?

Cement

Cement is composed of different raw materials, and although it is primarily made of limestone, there are more materials involved in the manufacturing process of the substance. Here are some of the raw materials typically used to make cement

  • Lime (CaO) – is arguably the most abundant material used for cement. About 60% of cement is made from lime, while the other 40% is occupied by other materials. Lime is used to provide the cement with strength and adhering qualities. Lime is a product of coal-seam fires, which are done by burning an outcrop or underground coal seam.
  • Silica (SiO2) – this material is mixed with the other raw materials of cement to increase the substance strength. However, silica increases the setting time for the cement, so it should only have 17% to 20% in the total cement mixture.
  • Alumina (Al2O3) – this material has the exact opposite purpose when compared to silica, as alumina is primarily used to quicken the setting time of the cement. But, alumina is also utilized to increase the strength of the substance.
  • Iron Oxide (Fe203) – is the material responsible for strengthening the adhesion of the cement with other materials. Iron oxide is also the material that gives color to the cement.
  • Gypsum (CaSO4 2H20) – this is a soft sulfate material that is primarily used to slow down the hydration process of cement, which would then help in controlling the setting or hardening time.

These materials are combined to form various types of cement, although there are a few extra materials added to some variants of cement to make them a bit different from the regular kinds of cement. Here are some of the popular and uncommon types or variants of cement that buyers can choose from.

Ordinary Portland Cement (OPC)

The most common type of cement is the Ordinary Portland Cement, also known as OPC. This type of cement is made by mixing limestone, chalk, and marl with alumina silicates like clay and shale. Ordinary Portland Cement has a very general purpose since it can be applied for almost all types of projects or designs, but it can also be used for masonry. So, it could be said that OPC is one of the most versatile types of cement.

Portland Pozzolana Cement (PPC)

The Portland Pozzolana Cement or PPC has a primary ingredient called pozzolans, which are synthetic and natural materials that are mixed to provide the cement with improved strength, especially when the cement is submerged under water. Because of its resiliency against excessive amounts of water, the Portland Pozzolana Cement is typically used to construct structures and buildings that are near the shore or underwater, like dams, water treatment centers, and hydroelectric plants.

Quick-Setting Cement

As evident in its name, the quick-setting cement has a very short setting time, which is advantageous to use for projects or construction plans that require a short construction time due to time constraints or the dangers that come with prolonging the construction of a building or structure. The quick-setting cement has the same capabilities as PPC in the sense that it can also be utilized for underwater construction, although it has a much faster setting time.

High Alumina Cement

High alumina cement is the type of cement that is typically used in construction areas or locations that have high temperatures. Moreover, it is also the best cement to use in establishments or buildings that are always exposed to high temperatures, like manufacturing factories, food processing plants, and workshops.

Colored Cement

Colored cement has varying colors that are produced by pigments that are suitable to be mixed with the raw materials of regular cement. Because only a few pigments go well with cement materials, there are only a few colors available for colored cement, with the most common ones being black, blue, red, green, and yellow. Colored cement is often used for decorating walls, although they are commonly molded in the form of floor tiles.

Cement Production Technology

concrete bricks

Before cement is manufactured, cement suppliers or manufacturers must first find raw materials, which they often collect from mines. Those raw materials, like limestone, would then be ground into fine powder to make them much easier to control or mold. The ground materials would be examined using laboratory x-ray fluorescence or XRF systems to check if the materials are pure and if they have major and minor oxides, which is essential in determining if they have the capabilities to create high-quality cement.

The fine powder produced from the raw materials is called raw meal, and this raw meal would then be placed inside a cement kiln, a thermally insulated chamber or oven, where the raw meal would be exposed to high temperatures that can go to 1450 degrees Celsius.

While the raw meal is being heated in the cement kiln, the chemical bonds of the materials within the raw meal are broken down and would be recombined into bigger compounds called clinker. The quality of the cement clinker produced by the cement kiln would depend on the raw materials used for the mixing process, as well as the percentage or abundance of specific materials in the raw meal.

After laboratory tests, the clinker would be ground into another batch of fine powder. Then, the powder would be transferred to a cement mill, where it would be mixed with gypsum to create cement. The powdered cement would then be poured onto their containers and shipped to various establishments.

Conclusion

Those are all the simple details of cement that you should know about when you are studying about it or just simply researching for fun. Keep in mind that cement comes in different forms, so the materials used for all types of cement can be difficult to enumerate since some manufacturers often add obscure chemicals to increase the strength, adhesion, setting time, and hardening time of their products. If you are planning on buying cement for a project or plan in the future, be sure to check reviews of various brands and products so that you will get the best and most suitable cement.

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