Question

Portland cement contains ‘X’ to enhance the setting time. What is ‘X’?

• A. \(CaSO_4.\frac 12 H_2O\)
• B. \(CaSO_4.2H_2O\)
• C. \(CaSO_4\)
• D. \(CaCO_3\)

Answer 1

The Correct Option is B

To answer the question, we need to identify the component in Portland cement that is responsible for enhancing the setting time. Portland cement commonly contains gypsum, which is chemically known as calcium sulfate dihydrate, represented by the chemical formula \(CaSO_4.2H_2O\). This component plays a crucial role in controlling the setting time of cement.

Let's examine the given options to identify which one corresponds to calcium sulfate dihydrate:

1. \(CaSO_4.\frac{1}{2} H_2O\): This is plaster of Paris, not used for enhancing setting time in cement.
2. \(CaSO_4.2H_2O\): This is gypsum, which is used in Portland cement to regulate setting time.
3. \(CaSO_4\): Anhydrous calcium sulfate, doesn't serve to control setting time as effectively as gypsum.
4. \(CaCO_3\): Calcium carbonate is typically a raw material in cement production but doesn't play a role in setting time.

Based on this analysis, the correct component 'X' that enhances the setting time in Portland cement is \(CaSO_4.2H_2O\).

Conclusion: The correct answer is \(CaSO_4.2H_2O\), which is gypsum. It is added to cement to slow down the setting process and allow for better workability after mixing with water.