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

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