Plasticiser is used for concrete to reduce the water / cement ratio, increase workability, reduce setting time and avoid cracking. It also decreases air content within the concrete, allowing it to be transported farther.
A good plasticiser also improves the durability of the concrete and makes it ten times more frost-resistant. This is important because freezing temperatures can cause damage to the cement.
Sodium lignosulphonate is a concrete water-reducing plasticizer that can reduce the hydration of concrete and improve its strength, compactness and impermeability. It is a versatile admixture that can be used with different types of concrete and can improve their properties, depending on the dosage.
Super plasticizers are high range water reducers that reduce the water requirement of concrete by up to 30 percent, thereby improving its strength and workability. They are often used in conjunction with other admixtures to produce high-slump, low-water-cement concrete that is strong and durable.
They are especially beneficial in concrete that is exposed to severe cold temperatures, as they reduce the moisture content and make the mix frost-resistant. They can also be added to precast concrete to help it stay in shape.
The adsorption of the molecules of the plasticizer on the surface of the cement particles is a key factor in its plasticizing effect. When these molecules attach to the cement grains, they form an ionic group that points outwards. This negative charge causes mutual repulsion between the cement particles. This results in entrapped air and the formation of a sheath of oriented water molecules that prevents close contact between the cement particles.