Gas Forming Admixtures
Definition:
- Gas forming admixtures are substances added to concrete mixtures to produce gas bubbles.
Purpose:
- Enhance the workability and plasticity of concrete.
- Create controlled air voids within hardened concrete.
Commonly Used Materials:
- Aluminum Powder: Reacts with alkaline compounds in cement to generate hydrogen gas.
- Hydrogen Peroxide: Decomposes to release oxygen gas.
- Calcium Carbide: Reacts with water to produce acetylene gas.
Mechanism:
- Chemical reactions between the admixture and the cement paste generate gas.
- The gas forms tiny bubbles within the mix.
Applications:
- Lightweight Concrete: Reduces the density of the concrete while maintaining structural integrity.
- Enhanced Workability: Improves the ease of handling and application, especially in low-slump applications.
- Thermal Insulation: Increases the thermal resistance due to air voids acting as insulators.
Advantages:
- Improved workability without additional water.
- Reduced density for applications requiring lightweight materials.
- Enhanced thermal properties.
Considerations:
- Proper dosage is critical to ensure uniform bubble formation.
- Excessive gas-forming admixtures can compromise the strength and durability of concrete.
- Compatibility with other admixtures needs to be verified.
These notes cover the fundamental aspects of gas forming admixtures, their applications, benefits, and considerations.
0 Comments