Which one of the following components of cement sets at the slowest rate: Dicalcium silicate, Tricalcium silicate, Tricalcium aluminate, Tricalcium aluminoferrite.

Options

A. Dicalcium silicate
B. Tricalcium silicate
C. Tricalcium aluminate
D. Tricalcium aluminoferrite.

Explanation

To determine which component of cement sets at the slowest rate, we need to analyze the four options provided: Dicalcium silicate, Tricalcium silicate, Tricalcium aluminate, and Tricalcium aluminoferrite.

### Step-by-Step Solution:

1. **Identify the Components**:
- The components of cement mentioned are:
- Dicalcium silicate (C2S)
- Tricalcium silicate (C3S)
- Tricalcium aluminate (C3A)
- Tricalcium aluminoferrite (C4AF)

2. **Understand Hydration Rates**:
- Each of these components hydrates at different rates when mixed with water:
- Tricalcium silicate (C3S) hydrates quickly and contributes to early strength.
- Dicalcium silicate (C2S) hydrates more slowly and contributes to strength development over a longer period.
- Tricalcium aluminate (C3A) hydrates very quickly but does not contribute significantly to strength.
- Tricalcium aluminoferrite (C4AF) hydrates at a moderate rate.

3. **Compare Hydration Characteristics**:
- Tricalcium silicate (C3S) has the fastest hydration rate and is responsible for the initial setting and strength.
- Dicalcium silicate (C2S) has a slower hydration rate and is known for contributing to long-term strength.
- Tricalcium aluminate (C3A) sets quickly but does not provide strength.
- Tricalcium aluminoferrite (C4AF) hydrates at a moderate rate.

4. **Conclusion**:
- Among the options, Dicalcium silicate (C2S) sets at the slowest rate compared to the other components. Therefore, the answer is **Dicalcium silicate**.

### Final Answer:
**Dicalcium silicate sets at the slowest rate among the components of cement.**