Air-entrained concrete is ordinary concrete. The only difference is, they contain controlled amount of air. These are intentionally entrained bubbles in the dimensions of microscopic range. A single cubic foot of air-entrained concrete contains billions of these air bubbles.
The presence of these air bubbles changes the nature of both fresh and hardened concrete. The primary benefit offered by the air bubbles in hardened concrete is the resistance it offers to freeze-thaw damage and scaling cause by deicing salt or chemicals. Most concrete contains some chemicals that expand due to freezing temperatures. Due to no room for expansion, large forces may rupture the surface of the concrete. These small air bubbles provide space for expansion and relieve the pressure.
Research shows that spacing and size of the air bubbles are important in assuring their proper action. Bubbles must be spaced within a distance of 0.0.1 inches. With new technologies it is not difficult to obtain these spacing.
Now let us look at some of the common questions are: if strength is reduced, if the proportion of concrete mixture is affected, can it be used in mild climates. The strength of air-entrained concrete is decided by the water/cement ratio as in any other concrete which is non air-entrained. Coming to the mix, air-entrained concrete is to be designed to take into account, for all the increase in air content. The content of water for air-entrained mix will be 3 to 5 gallons per cubic yard less than non air-entrained slump with the same mix. The sand content will is also to be less by about 90 – 125 pounds per cubic yard. Coming to climate, it is advised to use air-entrained concrete in southern climates.