Question

Gypsum is added to cement clinker to:
A. Decreases the rate of setting of cement.
B. Bind the particles of calcium silicate
C. Increase the tensile strength of the cement
D. Facilitate the formation of colloidal gel

Answer 1

Hint: Gypsum is a mineral and is hydrated calcium sulfate in chemical form. You should know that gypsum plays a very important role in controlling the rate of hardening of the cement.

Complete step by step answer:
Let us see what gypsum is.
Gypsum is naturally occurring mineral mined from deposits formed by ancient seabeds as a raw material. It is composed of calcium sulfate and water; it is used for a variety of manufacturing, industrial and agricultural uses. An important property of gypsum is that it is naturally fire-resistant. The chemical formula of gypsum is $CaS{ O }_{ 4 }.2{ H }_{ 2 }O$.

Let us see what happens when gypsum is added in the cement.
In the manufacturing process of cement, clinkers are formed. These cement clinkers are cooled down and added with a small amount of gypsum. The mixture is then sent to the final grinding process. The main purpose of adding gypsum in the cement is to slow down the hydration process of cement once it is mixed with water.
During the cement manufacturing process, upon the cooling of the clinker, a small amount of gypsum is introduced during the final grinding process. Gypsum is added to control the “setting of cement”. If not added, the cement will set immediately after mixing of water leaving no time for concrete placing.
Hence, Gypsum is added to the cement clinker to decrease the rate of setting of cement. Therefore, option A is the required answer.

Note: You should know that gypsum cement possesses considerably greater strength and hardness when compared to non-gypsum cement. The most common form of gypsum is rock gypsum.