Monday, October 7, 2013


A retarder is an admixture that slows down the chemical process of hydration so that concrete remains plastic and workable for longer time than concrete without the retarder

Retarders are used to overcome the accelerating effect effect of high temperature on setting properties of concrete in hot weather concreting.

Common materials added as retarding agents:
  1. Most commonly known retarder is calcium sulphate.It is interground to retard the setting of cement.
  2. Starches, cellulose products, sugars, acids or salts of acids.
  3. Common sugars are one of the most effective retarding agents.
  4. Other admixtures, which have been successfully used as retarding agents are Ligno sulphonic acids and their salts, hydroxylated carboxylic acids and their salts.

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