The setting time of Cement is increased by adding

Options

A. Clay
B. Silica
C. Gypsum
D. Limestone

Answer

To solve the question regarding the setting time of cement and the effect of various additives, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks which additive increases the setting time of cement.

2. **Identify the Additives**: The options provided are:
- Clay
- Silica
- Gypsum
- Limestone

3. **Research the Role of Each Additive**:
- **Clay**: Generally used to improve the plasticity and workability of cement but does not significantly affect the setting time.
- **Silica**: Typically used to enhance the strength and durability of cement but does not increase the setting time.
- **Gypsum**: Known to be added to cement to control the setting time. It slows down the hydration process, thus increasing the initial setting time.
- **Limestone**: Often used as a filler and can improve the workability but does not increase the setting time.

4. **Conclusion**: Based on the properties of these additives, gypsum is the only one that is specifically known to increase the setting time of cement.

5. **Final Answer**: The correct answer is **Gypsum** (Option 3).