Air Entrained Concrete
Air entrained concrete is made by mixing a small quantity of air-entrained agent or using air-entrained cement. These air-entraining agents produce of non-coalescing air bubbles.
These air bubbles act as flexible ball bearings and modify the properties of plastic concrete (such as workability, segregation, bleeding and finishing quality.
It also modifies the properties hardened concrete (such as resistance to frost action and permeability).
The commonly used air-entraining agents are natural wood resin, animal and vegetable fats and oil (such as tallow, olive oil e.t.c), various wetting agents (such as alkali salts, animal and vegetable fatty acids, etc).
This concrete is particularly suitable for places where there is a greater chance of frost attack.
Advantages of Air Entrained Concrete
Air Entrained concrete has the following advantages:
1) Its resistance to freezing and thawing is more.
2) Its workability is better than ordinary concrete.
3) It has more resistance to chemical attack.
4) The tendency of bleeding and segregation is less.
5) It reduces the cement content, sand content and thereby the cost of work.
6) The heat of hydration is less.
7) Its unit weight is less than ordinary concrete.
8) The alkali-aggregate reaction is less.