Which of the following is not an important ingredient present in Portland cement is

Options

A. `Ca_2SiO_4`
B. `Ca_3SiO_5`
C. `Ca_3Al_2O_6`
D. `Ca_3(PO_4)_2`

Answer

To determine which of the following is not an important ingredient present in Portland cement, we need to identify the main components of Portland cement.

### Step-by-Step Solution:

1. **Identify the Main Ingredients of Portland Cement**:
Portland cement is primarily composed of the following compounds:
- Tri-calcium silicate (Ca3SiO5)
- Di-calcium silicate (Ca2SiO4)
- Tri-calcium aluminate (Ca3Al2O6)
- Tetra-calcium aluminoferrite (Ca4Al2Fe2O10)

2. **List the Given Options**:
In the question, we need to analyze the options provided to see which one does not belong to the main ingredients listed above.

3. **Analyze Each Option**:
- **Option 1**: Tri-calcium silicate (Ca3SiO5) - This is a key ingredient.
- **Option 2**: Tri-calcium aluminate (Ca3Al2O6) - This is also a key ingredient.
- **Option 3**: Tetra-calcium aluminoferrite (Ca4Al2Fe2O10) - This is another important ingredient.
- **Option 4**: Phosphates - These are not a component of Portland cement.

4. **Conclusion**:
Since phosphates are not a significant ingredient in Portland cement, the correct answer is **Option 4**.

### Final Answer:
**Phosphates** are not an important ingredient present in Portland cement.

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