Special types of cement are used in concrete and masonry construction to serve specific functions. These functions include altering the setting or hardening behavior of concrete, producing different architectural effects, enhancing workability, imparting water retention and plasticity of masonry, resisting water penetration in walls or containment vessels, or reducing the cost of the cementing agent.
With the availability of several special types of cement, each kind provides a specific function in terms of application, performance, and durability. These special types of cement can be used at very high or very low temperatures, and some can even be used in acids.
One such special type of cement is silicate cement, which has a very high setting rate. Another example is barium and strontium cement, which are resistant to radioactive radiation. These special types of cement cater to specific requirements, and their usage depends on the nature of the project.
6 Special Types of Cements
Some of the special cement are described below:
1. Masonry Cement
In the past, lime mixed with sand was commonly used as mortar for laying bricks. However, in order to enhance the strength and speed of gaining strength, it became a widespread practice to combine lime with Portland cement. The ratio of cement to lime to sand typically ranges from 1:1:6 for heavy loads to 1:3:12 for light loads. However, cement sand mortars are often too harsh, which necessitates the addition of lime to make the work easier.
To avoid the need for mixing cement and lime, masonry cement was introduced. These cements are designed to provide plasticity and workability through the inclusion of limestone and an air-entraining agent. The water-retentive property of masonry cement, combined with its ease of use, makes it ideal for enhancing the adhesion of bricks or other building units.
2. Oil Well Cement
Oil well cement plays a crucial role in the drilling process of oil wells. It is used to fill the space between the steel lining tube and the well wall, grout up porous strata, and prevent water or gas from accessing oil-bearing strata.
However, the cement used in this process is subjected to very high pressure, and the temperature can rise up to 400 F. Therefore, the cement must have the capability of being pumped for up to about three years. This type of cement sets quickly after being set and hardens rapidly.
The selection of appropriate oil well cement is crucial for the success of oil drilling operations. It must be able to withstand the harsh conditions and provide the necessary support to the well structure. The properties of oil well cement are carefully considered, and the appropriate type is selected to ensure efficient and safe oil drilling operations.
3. Expanding Cement
Expanding cement is a type of cement that expands during the hardening process, unlike regular cement which typically shrinks and can result in unwanted shrinkage cracks. To avoid such issues, a combination of expanding cement and regular cement can be used in concrete mixes. This mixture will neither shrink nor expand, resulting in a more stable and reliable end product.
In addition to its use in concrete mixes, expanding cement can also be utilized in repair work where joints are opened. By filling these joints with expanding cement, a tight joint can be achieved after the expansion process is complete. This can be particularly useful in cases where a tight seal is necessary, such as in water containment structures or other similar applications. Overall, expanding cement offers a practical solution for improving the durability and longevity of concrete structures.
4. Sorel Cement
Sorel cement is a type of cement that is made by mixing ground calcinated magnesia with strong magnesium chloride. Once combined, it sets into a hard mass within 3-4 hours. One of the key advantages of Sorel cement is its accelerated rate of setting, which can be further improved by adding 1.5% calcium chloride. This makes it particularly useful during cold weather, when slower-setting cements can be problematic.
The preparation of Sorel cement involves a simple process of combining two key ingredients – ground calcinated magnesia and strong magnesium chloride. Once these components are mixed together, the cement will begin to harden and set within a relatively short period of time. The addition of calcium chloride can further increase the rate of hardening, making it an ideal choice for use in colder climates.
The rapid-setting properties of Sorel cement make it a popular choice in construction projects where time is of the essence. For example, it can be used to quickly patch up cracks and holes in concrete structures or to create temporary barriers. Additionally, its accelerated rate of setting makes it a practical choice for use in cold weather conditions, where slower-setting cements can be less effective. Overall, the use of Sorel cement provides a fast and efficient solution for many construction needs.
5. Trief cement
Trief cement is a type of cement that is very similar to blast furnace cement in composition. The primary difference between the two is that in Trief cement, the blast furnace slag is ground wet and separated from the cement. This grinding process results in a cement product that has some distinct advantages over ordinary Portland cement (OPC).
One of the main benefits of Trief cement is that it has smaller shrinkage compared to OPC. This is due to the finer grinding process used in the production of Trief cement. Because the blast furnace slag is ground wet and separately from the cement, the resulting product has a smaller particle size, which reduces the amount of shrinkage that occurs during the setting process.
Additionally, Trief cement has a smaller heat of evolution during setting than OPC. This means that the process of Trief cement setting releases less heat compared to OPC. This can be an advantage in certain applications where the temperature of the setting process needs to be closely controlled, or where excess heat could cause damage or other problems.
Overall, Trief cement offers a number of advantages over OPC, including reduced shrinkage and heat of evolution during setting. These benefits make Trief cement a popular choice in a variety of applications where high-quality, reliable cement products are required.
6. High Alumina Cement
High alumina cement is a type of cement that is produced by melting limestone and bauxite along with small amounts of silicon oxide and titanium oxide in a rotatory kiln at a temperature ranging from 1500-1600C. The resulting mixture is then ground to a fine powder using the same method used for manufacturing Portland cement.
The key constituents of high alumina cement are monocalcium aluminates, tricalcium pentaluminate, dicalcium silicate, and tetra calcium aluminoferrite. These elements are essential to the quality and characteristics of high alumina cement. Monocalcium aluminates contribute to the early strength of the cement, while tricalcium pentaluminate provides high-temperature strength. Dicalcium silicate aids in the setting and hardening of the cement, and tetra calcium aluminoferrite contributes to its durability and resistance to chemicals.
Overall, the production process of high alumina cement involves the fusion of specific raw materials at high temperatures followed by grinding to achieve the desired fineness. This process results in a cement with unique properties that make it useful in various applications such as in the construction of high-temperature furnaces, precast concrete products, and marine structures.
