Description of Air Entraining Admixtures

Air Entrainers:

               These are used to incorporate air in the form of minute bubbles in the concrete usually to increase the workability and resistance of freezing and Thawing.commonly used air entraining Admixtures are animal,vegetable oils,natural wood,Alkaline salts of sulphonated  organic compounds.

Factor Effecting the amount of air entraining:

               The manufacture of air entrained concrete is complicated by the fact that amount of air entrainment in a mix is effected by many factors.
The important factors are;

• Type and quantity of air entraining agent is used.
• Water by cement ratio is fixed.
• Types and grading of aggregates is done.
• Mixing Time
• Temperature
• Type of Cement
• Influence of Compaction
• Admixtures other than air entraining admixtures are used.

The Effect of Air Entrainers on the properties of the concrete:

            The air entraining will be affect directly on following properties of the concrete

• Increase in the resistance of freezing and thawing.
• Improvement in the workability.
• Reduction in the strength.

Incidentally air entrainment will also effect the properties of the concrete in the following ways

• Reduces the tendency of seggration
• Reduces the bleeding
• Decrease the permeability.
• Increase the Resistance.
• Permits the sand content which improves the plasticity and early finishing.
• Reduces the cement content,cost and heat of hydration.
• Reduces the unit weight.
• Permits the reduction in water content.
• Reduces the alkali-aggregate reaction.
• Reduces the Modulus of the Elasticity.