Pavements are in direct contact with the atmosphere and effects very extensively with the change in environmental conditions. To make rigid pavements safe against environmental fluctuations like freeze thaw effect, It is necessary to entrained air in hardened concrete.
Entrained air improves resistance against freeze thaw effect, when pavement will be exposed to cold temperatures, corroding chemicals and water.
Entrained air has various other benefits too. Entrained air improves the workability of fresh concrete and that ease during placing of fresh concrete in pavements and its manipulation will be easy. Entrained air improves resistance against sulfate and alkali silica.
Air is entrained in concrete by adding air entraining admixtures during batching of concrete. There are various cement available in the market that also entrained air in the concrete. Since cement is the most expensive component of concrete, therefore in pavement air entraining admixtures are being used.
Purpose Of Entrained Air
Main purpose of air entraining admixtures in concrete is to make concrete durable and when durability of concrete enhances, then in returns serviceability time also increases. Durability of concrete depends on the size and spacing between two air bubbles and there is a little dependency on the amount of air entrained.
If spacing between air bubbles varies throughout the volume of concrete, then in returns resistance against weather also varies. Therefore, it is necessary to well aware all the perspective in mind while calculating the amount of entrained air.
Some entrained air also loss during transporting from batch to the field, because of vibration in the body of truck. For better results add an extra amount of entrained air in fresh concrete, so that loss will not affects the properties of concrete after placing.