Admixtures_in_Concrete_Presentation.pptx

Admixtures_in_Concrete

1. Admixtures in Concrete Purpose, Properties, and Applications

2. Accelerators Purpose: Speed up setting time and early strength gain Properties: Reduces setting time, increases early strength, useful in cold weather Applications: Early removal of formwork, precast concrete, winter concreting Examples: Calcium chloride, triethanolamine [Image: Concrete with accelerator use]

3. Retarders Purpose: Delay setting time of concrete Properties: Slows down hydration, controls setting in hot weather Applications: Mass concreting (dams, bridges), long-distance transport Examples: Gypsum, sugar, lignosulphonates [Image: Concrete pour in hot weather]

4. Water-Reducing Admixtures Purpose: Reduce water content for same workability Properties: Increases workability, strength, and durability Applications: High-strength concrete, pumped concrete Examples: Lignosulphonates, polycarboxylates [Image: Slump test comparison]

5. Air-Entraining Agents Purpose: Introduce air bubbles in concrete Properties: Improves freeze-thaw resistance, reduces bleeding Applications: Pavements, hydraulic structures in cold regions Examples: Vinsol resin, detergents [Image: Microscopic air bubbles in concrete]

6. Superplasticizers Purpose: Increase workability without extra water Properties: Reduce water by 20–30%, high-performance concrete Applications: Prestressed concrete, self-compacting concrete Examples: Sulphonated melamine formaldehyde, PCE [Image: Flowing/self-compacting concrete]

7. Comparison of Admixtures Accelerators – Early strength gain Retarders – Delay setting Water Reducers – Improve workability & strength Air Entraining – Freeze-thaw resistance Superplasticizers – High flow & strength [Image: Summary table illustration]