Retarders:

Retarders are the substances which are used to retard the setting of cement thereby increasing the setting time of cement. When pumping of concrete is required for long distances, retarders are used so which concrete does not get stiffened during pumping process. Calcium lingo sulfonate is one compound, which is extensively being used for these purposes.

Water-repelling Agents

These are the materials which when mixed with concrete; repel the water from concrete and to make the concrete more waterproof. These agents are used when the concreting is going on in a very wet condition, to avoid the entry of water into the concrete.

Workability Agents:

The workability of concrete increases by using workability agents. Workability agents give smoothness and reduce the bleeding of concrete. These materials are useful in cases when the aggregate is deficient in fines and to achieve workability requirement even with low water content ratio. Commonly used workability agents are fly ash, bentonite clay, finely divided clay, talc, hydrates lime, etc.