Portland cement is manufactured by using

Options

A. lime stone, clay and sand
B. lime stone, gypsum and sand
C. lime stone, gypsum and alumina
D. lime stone, clay and gypsum.

Explanation

To determine the materials used in the manufacture of Portland cement, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Components of Portland Cement**:
- Portland cement is primarily made from three key raw materials: limestone, clay, and gypsum.

2. **Understand the Role of Each Component**:
- **Limestone**: This is the main source of calcium carbonate (CaCO3), which is essential for the formation of clinker.
- **Clay**: Provides silica (SiO2) and alumina (Al2O3), which are necessary for the chemical reactions that occur during the cement manufacturing process.
- **Gypsum**: This is added to control the setting time of the cement.

3. **Manufacturing Process Overview**:
- The raw materials (limestone and clay) are mixed and heated in a kiln to produce clinker.
- After the clinker is formed, gypsum is added to the mixture to produce Portland cement.

4. **Final Product**:
- The final product is Portland cement, which can then be mixed with sand, gravel, and water to create concrete.

5. **Select the Correct Option**:
- Based on the above information, the correct option that includes all necessary components for the manufacture of Portland cement is:
- **Option D**: Limestone, clay, and gypsum.

### Conclusion:
Portland cement is manufactured using limestone, clay, and gypsum. Therefore, the correct answer is **Option D**.

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