What is Polycarboxylate Powder?

What is Polycarboxylate Powder?

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What is polycarboxylate superplasticizer?
polycarboxylate superplasticizer is a high-performance water-reducing agent and a cement dispersant used in cement concrete applications. It is widely used in highways, bridges, dams, tunnels, high-rise buildings and other projects.
Polycarboxylate superplasticizers were introduced in the 1980s. At present, polycarboxylic acid-based high-performance water reducing agents can generally be divided into two categories: one is based on maleic anhydride as the main chain and grafted with different polyoxyethylene (EO) or polyoxypropylene (PO) branch chains; another methacrylic-based backbone branch (EO) or (PO) branch.

Polycarboxylate superplasticizer are mostly anionic surfactants. The mechanism is as following:
Dispersity
The molecules of polycarboxylate superplasticizer can be directionally adsorbed on the surface of cement particles, so that the surfaces of cement particles carry the same charge (usually negative charge), forming electrostatic repulsion, which promotes the mutual dispersion of cement particles, destroys the flocculation structure, and releases the wrapped particles.  Part of the water participates in the flow, thereby effectively increasing the fluidity of the concrete mixture.
Lubrication
The hydrophilic group in the polycarboxylate water-reducing agent is very polar, so the adsorption film of the polycarboxylate water-reducing agent on the surface of the cement particles can form a stable solvated water film with water molecules. This water film has good properties.  The lubrication effect can effectively reduce the sliding resistance between cement particles, thereby further improving the fluidity of concrete.
Steric Hindrance
The closer the polycarboxylate superplasticizer cement particles are to each other, the greater this steric hindrance effect will be.  This effect increases the slump retention effect of concrete.

Performance characteristics
Improve the mechanical properties of concrete. Because it has good water-reducing effect and increases the structural density of concrete, it can improve the compressive, bending and tensile strength.
Excellent plastic retention properties, so the polycarboxylic acid-based water reducing agent has high dispersion properties and can maintain this performance for a long time, achieving excellent plastic retention properties of the concrete mixture.
Effectively improve the durability of concrete, reduce the alkali-aggregate reaction of concrete, and improve the freeze-thaw resistance of concrete.
The water-reducing rate is good. The polycarboxylic acid-based water-reducing agent has good water-reducing performance at low dosage (generally 0.2% - 0.3%, equivalent to the mass ratio of dry basis to cement), especially in high-grade concrete (C50) is more obvious, and its maximum water reduction rate can reach 40%;
It has good shrinkage resistance. Concrete mixed with polycarboxylic acid-based water reducing agent can effectively improve its shrinkage and creep properties. The concrete has good stability and reduces the risk of cracks.
Early strengthening and reinforcing effect are good. Under the same conditions, the early strength and reinforcing effect of concrete mixed with polycarboxylic acid-based water-reducing admixtures are higher than other types of water-reducing admixtures.
With excellent water retention properties, the bleeding of concrete mixed with polycarboxylic acid-based water reducing agent is significantly lower than that of ordinary concrete, and there is no segregation, making construction work easier.
Polycarboxylate superplasticizer is mainly used to prepare concrete with low water-cement ratio, high strength, self-compacting and high durability. It is the main development direction of high-performance concrete water-reducing agent.