Question

In handling air-entraining admixtures the beneficial amount of entrained air depends upon certain factors like

1. Type and quantity of air-entraining agent

2. Water-cement ratio of the mix

3. Strength of aggregates

4. The extent of compaction of concrete
1. 1, 2 and only
2. 1, 2 and 4 only
3. 1, 3 and 4 only
4. 1, 2, 3 and 4

Answer 1

Correct Answer - Option 2 : 1, 2 and 4 only

The following table gives the detail information of admixtures with their examples.

Sr. No.	Admixtures	Properties	Examples
1.	Accelerator	They accelerate the hardening process. Speed the setting time and thus cure time starts earlier.	Calcium chloride, soluble carbonates, silicates, fluorosilicates, etc.
2.	Retarder	It slows down the chemical process of hydration, so used in Hot weather conditions.	Sugar, carbohydrates, zinc salts, borates, etc.
3.	Air Entraining	They produce air bubbles in the concrete, which act as flexible ball bearings and increase the workability of concrete. The entrained air which handles the air-entraining admixture depends on the following factors, 1. The workability requirement of concrete.Type and quantity of air-entraining admixture 2. Water cement ratio of the mix. 3. The extent of compaction of concrete. The entrained air deals with the workability requirement of concrete. The strength of aggregate does not show the workability of concrete.	wood resins, Animal and vegetable fats, and oils, alkali salts, etc.
4.	Plasticizer	Plasticizers are those admixtures that reduce water requirement and increase the workability of concrete.	Lignosulphonates, salts of sulphonates, hydrocarbons, carbohydrates, etc.
5.	Superplasticizer	These are improved versions of plasticizers also known as high range water reducers. Using this helps in the production of flowing, self-leveling, self-compacting, and high strength, and high-performance concrete.	Modified lignosulphonate, sulfonated melamine-formaldehyde.