Question

Consider the following statements about the air entraining admixture in concrete:
1.Improve workability
2. Improve durability
3. Reduce segregation during placing
4. Decrease concrete density
Which of these statements are correct?

• A. 1, 2, 3 and 4
• B. 1 and 2 only
• C. 2 and 3 only
• D. 3 and 4 only

Answer 1

The correct option is A 1, 2, 3 and 4

Air-entraining admixtures help to incorporate a controlled amount of air, in the form of millions of minute non-coalescing bubbles. These air bubbles act as flexible ball bearings and modify the properties of plastic concrete regarding workability, segregation, bleeding and finishing quality of concrete. It also modifies the properties of hardened concrete regarding its resistance to frost action, permeability and durability. For the same workability and strength, the air-entrained concrete contains approximately 5% less solid material and hence has lower density. Some of the air entraining agents are natural wood resins, various sulphonated compounds and some animal and vegetable fats and oils such as tallow, olive oil and their fatty acids such as stearic and oleic acids.