Question

Which of the following is not an ingredient of clinker cement? (a) calcium silicate (b) aluminium silicate (c) calcium aluminium silicate (d) gypsum

Short answer

(a) Calcium silicate (b) Aluminium silicate (c) Calcium aluminium silicate (d) Gypsum Answer: (d) Gypsum

Step-by-step solution

Understanding the composition of clinker cement

Clinker is the primary component used in producing cement. Its typical composition includes calcium silicates, aluminium silicates, and calcium aluminate silicates. After the clinker is produced, it is combined with other materials, such as gypsum, to form the final cement.

Evaluating the given options

Now that we know the typical composition of clinker cement, we can evaluate the given options: (a) Calcium silicate - This compound is a common component of clinker cement. (b) Aluminium silicate - This compound is also a common component of clinker cement. (c) Calcium aluminium silicate - This compound is another common component of clinker cement.

Identifying the option that is not an ingredient of clinker cement

Based on the above evaluation, we can see that the first three options are all common components of clinker cement. The only remaining option is: (d) Gypsum - This compound is not an ingredient of clinker cement itself, but it is added to the clinker during the production of the final cement mixture.

Conclusion

Therefore, the correct answer is (d) gypsum, as it is not an ingredient of clinker cement.

Key concepts

Calcium Silicates

Calcium silicates are a crucial component of clinker cement. They are responsible for providing strength to the cement once it sets. Two of the primary types of calcium silicates found in cement are alite (also known as tricalcium silicate) and belite (dicalcium silicate).

• Alite: This compound reacts with water quickly and is primarily responsible for the initial set and early strength of cement.
• Belite: It reacts slower than alite and contributes to the long-term strength of the cement.

Together, these compounds ensure that the cement has both immediate and lasting strength, making it a reliable construction material. Calcium silicates also play a significant role in the hydration process, a chemical reaction that occurs when cement is mixed with water.

Aluminium Silicates

Aluminium silicates, although not as prominent as calcium silicates in the composition of clinker cement, still hold an essential role. These silicates, primarily in the form of calcium aluminates, contribute to certain properties of cement.

• They influence the setting time of cement, controlling how quickly or slowly it hardens.
• Aluminium silicates provide resistance to chemical attack, enhancing the durability of the concrete structure.

Although they do not directly contribute to the strength of the final product, their impact on setting time and resilience is vital for construction efficiency and longevity. Urban structures benefit from their presence, especially in environments exposed to aggressive chemical conditions.

Calcium Aluminium Silicates

Calcium aluminium silicates combine the properties of both calcium and aluminium silicates. These compounds are essential in determining the early structural characteristics of cement.

• They assist in heat management during the setting process, ensuring that cement cures evenly.
• These silicates also contribute to the immediate strength of the cement, essential for construction projects needing rapid turnarounds.

By managing heat and supporting quick setting, calcium aluminium silicates help prevent defects like cracking or crazing, which enhance the longevity of concrete structures. Their dual-action ensures that cement is adaptable to various building situations, providing both stability and resilience.

Gypsum in Cement Production

Gypsum is an additive used in cement production, rather than a component of the clinker primarily. Although not part of the clinker, it plays a crucial role during the final stages of cement manufacturing.

• Gypsum controls the setting time of cement, preventing it from hardening too quickly, which would complicate the building process.
• It provides smoothness in the cement mixture, making it easier to work with.

By regulating the time it takes for cement to set, gypsum allows builders the necessary timeframe to adjust and perfect their construction projects before the cement solidifies. This addition means that projects can maintain flexibility without sacrificing quality, making gypsum an indispensable part of modern cement production.