Question

What is the purpose of adding gypsum to cement? 

• A. To give a hard mass
• B. To facilitate the hydration of cement
• C. To slow down the process of setting
• D. To speed up the process of setting

Answer 1

The Correct Option is C

The purpose of adding gypsum to cement is primarily to control the setting time of the cement. This is crucial for the construction industry as it allows the cement to harden more slowly, which gives workers enough time to work with the concrete before it sets in place.

Let's explore how this works and why the other options are incorrect:

1. To slow down the process of setting:
   Cement begins to set once it is mixed with water due to the chemical reaction known as hydration. Gypsum is added to slow down this reaction, delaying the setting time, allowing for proper mixing, transporting, and placing of concrete. This is the correct answer.
2. To give a hard mass:
   This is not the specific purpose for adding gypsum. While gypsum aids in achieving the desired hardness over time, its main function is not to provide a hardening effect.
3. To facilitate the hydration of cement:
   Gypsum does not facilitate hydration; rather, it moderates it to prevent the cement from setting too quickly.
4. To speed up the process of setting:
   Gypsum actually does the opposite; it slows down the setting process. Accelerators, such as calcium chloride, are used to speed up the setting process.

In conclusion, gypsum is used in cement to regulate the setting time and prevent it from setting too quickly, which is vital for ensuring the workability of the cement mix in practical applications.