ADMIXTURES AND TYPE OF ADMIXTURES USES OF ADMIXTURES - KPSTRUCTURES.IN

ADMIXTURES AND TYPE OF ADMIXTURES USES OF ADMIXTURES

DEFINITION :-

•The Chemicals Used To Improve The Properties Of Concrete & Cement Know As Admixtures.

•Properties Like Strength, workability, Durability, Hardening Time etc.

•Admixtures Can Be Divided Into 2 Groups Or Forms That Is:

                              1) Chemical Admixtures

                              2) Mineral Admixtures

Before Going With Types Lets Discuss About Functions Of Admixtures

Function Of Admixtures :-

•To improve workability of concrete.

•To reduce evolution of heat.

•To improve durability.

•To accelerate setting & hardening thus produce high early strength.

•Reduce shrinkage during setting & hardening.

•To reduce some chemical reactions.

Types Of Admixtures :-

Chemical Admixtures :-

  • Accelerator :-

-Added to increase the rate of hydration of concrete mix which then lead to increase in the rate of development of strength and greater heat evolution

-Shorten the setting time

-More rapid gain of strength

-Possible to cracking due heat

  • Water Reducing Admixtures :-

– Used to reduce amount of water necessary to produce a concrete

– To obtain specific  strength at lower cement content

– Disadvantage, it has risk of corrosion

  • Shrinkage Reducing Admixtures :-

– Able to reduce the amount of shrinkage that occurs as hardened of concrete

  • Super plasticize :-

-Allows the particles to be more workable where it enable working with low w/c ratio

-Enhances hydration process, increase strength

-Advantage is Decreased time to place and finish and also Accelerator curing period

  • Air Entraining Admixtures :-

– Able to reduce segregation tendency and control of bleeding

-Workability increases, increased durability etc

  • Retarding Admixtures :-

– Prolong or delay the setting time of cement paste in concrete

– Used in hot weather condition

  • Corrosion Inhibitors :-

– Able to reduce the rate of corrosion to a level that major damage to concrete will be avoided or at least greatly reduced

  • Alkali Aggregate Reaction Inhibiting Admixture :-

– Lithium And Barium Salts Can Reduce The Expansion And Cracking Associated With Alkali Silica Reaction

Mineral Admixtures :-

  1. Pozzolanas
  2. Fly Ash
  3. Silica Fume
  4. Rice Husk Ash
  5. Metakaoline
  6. Blast Furnace Slag

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