What is an Admixture | Functions of Admixtures

Chemical Admixtures In Concrete

What are Admixtures

Admixtures are artificial or natural materials added to the concrete besides cement, water and aggregate to improve certain property of concrete during casting or setting or service stage.

To improve the properties of the concrete required. It can be divided in 2 groups that is:
  • Chemical
  • Mineral
Chemical Admixtures In Concrete

Chemical Admixtures In Concrete

 

Functions of Admixture

As explained above, admixtures are added to modify concrete properties. Major functions and advantages of using admixtures are detailed below.

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

Types of chemical admixture used are:

Nowadays, lot of additives are used in concrete mixes to enhance its properties. Depending on the specific function or action on the concrete property, it can be classified into following

  • Accelerator
  • Water reducing Admixture
  • Superplasticizer
  • Air Entraining
  • Retarding
  • Corrosion Inhibitors
  • Alkali-Aggregate Reaction Inhibiting
  • Shrinkage Reducing
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