Understanding Cement Strength Components

Cement is a crucial binder in concrete, and its strength development comes from the hydration reactions of its various clinker compounds. The question asks specifically which component provides the ultimate strength to cement. Let's examine the main components:

Key Cement Compounds and Strength Contribution

The primary compounds in Portland cement clinker are:

• Tricalcium Silicate ($C_3S$ or Alite): This compound hydrates rapidly and is primarily responsible for the early strength of cement (within the first 7 days).
• Dicalcium Silicate ($C_2S$ or Belite): This compound hydrates much more slowly than $C_3S$. Its hydration products contribute significantly to the later or ultimate strength of the cement, typically observed after 7 days and continuing for a long period.
• Tricalcium Aluminate ($C_3A$): This compound hydrates very quickly but contributes relatively little to the strength. It influences the setting time and can cause flash set if not controlled.
• Tetracalcium Alumina Ferrite ($C_4AF$): This compound hydrates relatively quickly but contributes very little to the strength. It mainly affects the color of the cement.

Di-calcium Silicate's Role in Ultimate Strength

Based on the hydration characteristics and strength development, Di-calcium silicate ($C_2S$) is the component that provides the ultimate strength. While $C_3S$ gives initial grab, $C_2S$ continues the hardening process over time, leading to the final, long-term strength required for structural integrity.

Analysis of Options

The options provided are:

1. Tricalcium silicate ($C_3S$): Responsible for early strength.
2. Di calcium silicate ($C_2S$): Responsible for ultimate strength.
3. Tricalcium aluminate ($C_3A$): Affects setting time, minimal strength contribution.
4. Tetra calcium alumina ferrite ($C_4AF$): Minimal strength contribution.

Therefore, the component providing the ultimate strength is Di-calcium silicate.