Which of the following is not present in portland cement?

Options

A. `Ca_(3)Al_(2)O_(6)`
B. `Ca_(3)SiO_(5)`
C. `Ca_(2)SiO_(4)`
D. `Ca_(3)(PO_(4))_(2)`

Explanation

To determine which of the following substances is not present in Portland cement, we need to analyze the composition of Portland cement. The main components of Portland cement include:

1. **Tricalcium Silicate (Ca3SiO5)**: This compound is a significant constituent of Portland cement and contributes to its strength and hardening properties.

2. **Dicalcium Silicate (Ca2SiO4)**: Another important component, dicalcium silicate also plays a role in the strength and durability of the cement.

3. **Tricalcium Aluminate (Ca3Al2O6)**: This compound is present in smaller amounts and affects the setting time and strength development of the cement.

4. **Tetra Calcium Aluminoferrite (Ca4Al2Fe2O10)**: This component is also found in Portland cement and contributes to its properties.

5. **Calcium Sulfate Dihydrate (Gypsum, CaSO4·2H2O)**: Gypsum is added to control the setting time of the cement.

Now, let's consider the options provided in the question. We need to identify which of these is not a component of Portland cement.

After reviewing the components listed above, we find that:

- **Calcium Phosphate** is not included in the composition of Portland cement.

Thus, the correct answer is that Calcium Phosphate is not present in Portland cement.

### Final Answer:
Calcium Phosphate is not present in Portland cement.