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Friday, February 15, 2013

PowerPoint Presentation On ADMIXTURES


ADMIXTURES Presentation Transcript:
1. What Are Admixtures?
Admixtures are chemical substances (other than fine and coarse aggregates, cement, or water), which are added in small amounts just before or during the mixing stage to concrete products.

Over decades, attempts have been made to obtain concrete with certain desired characteristics such as high compressive strength, high workability, and high performance and durability parameters to meet the requirement of complexity of modern structures.

To improve workability of fresh concrete
To improve durability by entrainment of air
To reduce the water required
To accelerate setting & hardening & thus to produce high early strength
To aid curing
To impart water repellent / water proofing property

4. To cause dispersion of the cement particles when mixed with water
To retard setting
To improve wear resistance (hardness)
To offset / reduce shrinkage during setting & hardening
To cause expansion of concrete and automatic prestressing of steel
To aerate mortar / concrete to produce a light-weight product

5. To impart colour to concrete
To offset or reduce some chemical reaction
To reduce bleeding
To reduce the evolution of heat

6. Types of Admixtures
Chemical admixtures
Mineral admixtures

Water-reducing admixture / Plasticizers
They achieve a higher strength by decreasing the water cement ratio at the same workability as an admixture free mix. To achieve the same workability by decreasing the cement content so as to reduce the heat of hydration in mass concrete. To increase the workability so as to ease placing in accessible locations

8. Water reduction is more than 5% but less than 12% The commonly used admixtures are Ligno-sulphonates and hydrocarbolic acid salts. Plasticizers are usually based on lignosulphonate, which is a natural polymer, derived from wood processing in the paper industry

9. Super Plasticizers
These are more recent and more effective type of water reducing admixtures also known as high range water reducer. They increase fluidity and following properties: Flowing Self-leveling Self-compacting concrete Penetration and compaction around dense reinforcement

10. For more info. please refer our PPT, Thanks.

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