Question

Gypsum is added to clinker during cement manufacture to (1) decrease the rate of setting of cement (2) make the cement impervious (3) bind the particles of calcium silicate (4) to facilitate the formation of colloidal gel

Short answer

Option (1): Decrease the rate of setting of cement.

Step-by-step solution

Identify the Function of Gypsum

Gypsum is added to the clinker during the manufacture of cement. It is important to understand what role gypsum plays in the cement production process.

Analyze the Options

Look at the options provided:(1) Decrease the rate of setting of cement(2) Make the cement impervious(3) Bind the particles of calcium silicate(4) Facilitate the formation of colloidal gel

Match Gypsum's Role with the Correct Option

Gypsum acts as a retarder in cement. Its primary role is to decrease the rate at which cement sets, preventing it from setting too quickly after mixing with water. This helps in the handling and placement of cement.

Conclude the Correct Option

Based on the analysis, the correct role of gypsum is to decrease the rate of setting of cement, which corresponds to option (1).

Key concepts

Cement Manufacturing

Cement manufacturing is a detailed process that transforms raw materials into a reliable and versatile building material. First, raw materials like limestone, clay, and sand are extracted and crushed. The crushed materials are then mixed and heated at high temperatures in a kiln to produce clinker, the key component in cement. The clinker is cool, ground to a fine powder, and mixed with other additives, including gypsum. This transformation process ensures that the final cement product is strong, durable, and suitable for a wide range of construction applications.
Cement manufacturing also involves significant quality control throughout to guarantee that the final product meets the required standards. Each stage, from raw material extraction to the final milling, is carefully monitored. This precise attention to detail results in high-quality cement that performs well in both straightforward and complex building projects.

Setting Rate of Cement

The setting rate of cement refers to the speed at which the cement hardens after water is added. This is a critical aspect of cement performance, influencing both workability and durability. If cement sets too quickly, it can reduce the time available for mixing, transporting, and placing the concrete. This can result in weak structures and poor adherence to the surrounding materials. On the other hand, if it sets too slowly, construction processes can be delayed, and the strength of the final product can be compromised.
The setting rate is controlled through the careful adjustment of the cement composition and the use of additives, such as gypsum. By managing how quickly the cement sets, manufacturers can ensure that the concrete remains workable during construction but also reaches its designated strength in a timely manner. It's a delicate balance that requires precise engineering and an understanding of the material properties.

Role of Gypsum

Gypsum plays a pivotal role in the cement manufacturing process. One of its primary functions is to act as a retarder, slowing down the setting rate of cement. Without gypsum, cement would set almost immediately after water is added, making it impractical for most construction purposes. The addition of gypsum allows for a manageable setting time, providing flexibility to builders and ensuring that the concrete can be properly mixed, transported, and placed before it hardens.
Gypsum achieves this by interacting chemically with the calcium aluminate in the cement. This reaction slows down the hydration process, giving workers more time to work with the material. Moreover, gypsum also helps in improving the overall quality and durability of the cement. By preventing flash setting, it ensures that the cement hardens uniformly, reducing the risk of cracks and structural failures in the long term.

• Gypsum is crucial for controlling the setting time of cement.
• It enhances the workability of cement.
• Aids in reducing the risk of cracking and structural failures.