Hydration of Cement
Definition:
- Hydration of cement refers to the chemical reaction between cement and water, which leads to the setting and hardening of cement.
Key Processes:
Initial Mixing:
- Cement particles react with water.
- Formation of a gel-like substance.
Setting:
- Initial stiffening of the cement paste.
- Chemical reactions start slowing down.
- Not suitable for working or molding.
Hardening:
- Continued hydration.
- Development of strength over time.
Chemical Reactions:
- Primary components involved in hydration:
- Tricalcium silicate (C3S)
- Dicalcium silicate (C2S)
- Tricalcium aluminate (C3A)
- Tetracalcium aluminoferrite (C4AF)
- C3S (Tricalcium Silicate): Fast reaction, responsible for early strength.
- C2S (Dicalcium Silicate): Slower reaction, contributes to long-term strength.
- C3A (Tricalcium Aluminate): Reacts quickly with water, causes heat evolution.
- C4AF (Tetracalcium Aluminoferrite): Minor contributor to strength.
Heat of Hydration:
- Exothermic reaction.
- Heat released, significant during early stages.
- Important for curing processes.
Stages of Hydration:
- Induction/ Dormant Period:
- Little heat evolution.
- Allows for workability.
- Acceleration Period:
- Rapid heat production.
- Mass formation of calcium-silicate-hydrate (C-S-H) and calcium hydroxide.
- Deceleration Period:
- Gradual completion of reactions.
- Strength development continues at a slower rate.
Products of Hydration:
- Calcium-Silicate-Hydrate (C-S-H):
- Primary product.
- Contributes to the strength and permeability of cement.
- Calcium Hydroxide (Ca(OH)2):
- By-product.
- Contributes to the alkalinity of cement.
Importance in Construction:
- Understanding hydration is crucial for:
- Controlling setting times.
- Ensuring strength development.
- Managing heat generation.
- Improving durability and longevity of structures.
These notes focus on the main processes, chemical reactions, and significance of the hydration of cement, giving a comprehensive overview necessary for study purposes.
0 Comments