An admixture in concrete is a substances or mixture of substances , other than water, aggregates, and cement that is added to the concrete mix to modify its properties . Admixture are typically used to improve the workability , durability , or strength of concrete or to facilitate specific construction requirements.
There are several types of admixtures.
1.Accelerators.
These speed up the setting and curing time of concrete , often used in cold weather condition .Often includes calcium chloride .
Increases heat of hydration.
Faster setting time - Accelerator reduces the time required for concrete to set, enabling quicker project progress.
Cold weather application - useful in low temprature to counteract delayed setting caused by cold weather.
Increases setting time admixture
2. Retarder .
These slow down the setting time of concrete , which is useful in hot weather or when a delay in setting is desired.
Ideal for hot temprature- Reduces the risk of rapid setting and cracking in high temprature condition.
Commonly used in sugar or lignosulfonate.
3. Plasticizers ( water - reducing agent ).
These reduce the amount of water needed in the mix while maintaining the same workability , leading to stronger and more durable concrete .Enhances concrete workability.Lower water content , improves strength . Enhances concrete pumpability.
Polycarboxylate ethers commonly used.
Water reducing admixture
4. Super plasticizers.
These are a more advanced version of plasticizers , capable of significantly increasing the workability of concrete without increasing the water content.
Minimizes water demands up to 30% .
Low workability , extremely high strength .
Avoids things like bleeding, segregation etc.
Used in highly Reinforced members
5. Air- entering Agents.
These creats tiny air bubbles in the concrete, improving its resistence to freeze - thawing cycles and increasing its durability.
Improves workability, durability and cohesion.Used in extreme cool places.
Introduces micro bubbles for durability .
Fatty acid salts are widely used.
Bubbles removable admixture
Why needed admixture in concrete.
1. Enhance workability.
2. Improve durability.
3.Accelerator and retarder the setting time .
Accelerators means speed up the setting time, and retarder means Slow down the setting time.
4.Reduces water content.
5. Control cracking and shrinkage.
6. Improve strength and performance.
Comments
Post a Comment