Role of Superplasticizers in concrete
The water cement (W/C) ratio is an important factor deciding the durability of concrete.
Its impermeability, strength, and durability are directly proportional to this and so this has to be kept small.
In normal cement pastes, when cement particles come into close contact with each other, there is a tendency for the pastes to form large ‘floes’ due to attractive forces acting between them.
Because of such formation, more water than required is added.
This increases the W/C ratio and affects the concrete’s properties.
These can be overcome by adding superplasticizers at the appropriate stage of mixing the ingredients of concrete.
It helps to reduce inter-particle attraction between cement particles and to disperse the cement particles with less water.
These superplasticizers actually form a chain of molecules and are completely absorbed into the system.
Superplasticizers are sulphonated melamine formaldehyde condensates or sulphonated naphthalene formaldehyde condensates.
These are used to produce ‘flowing’ concrete in cases where placing in inaccessible locations is required.
They are also used in the production of high strength concrete using normal workability but a very low water/cement ratio so as to reduce the heat of hydration in mass concrete.
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