The role and working principle of polycarboxylate superplasticizer in concrete

1. Dispersion

After the cement is mixed with water, due to the molecular attraction of the cement particles, the cement slurry forms a flocculation structure, so that 10-30% of the mixing water is wrapped in the cement particles and cannot participate in free flow and lubrication, thus affecting the concrete mixing. fluidity of the compound. When the polycarboxylate superplasticizer is added, the molecules of the polycarboxylate superplasticizer can be adsorbed on the surface of the cement particles directionally, so that the surface of the cement particles is charged with the same charge, forming electrostatic repulsion, so that the cement particles disperse each other and destroy the flocculation structure. , releasing the encapsulated water and participating in the flow, thereby effectively increasing the fluidity of the concrete mixture.

2. Lubrication

The hydrophilic group in the polycarboxylate superplasticizer PCE is very polar, so the adsorption film of the polycarboxylate superplasticizer on the surface of the cement particles can form a stable solvated water film with water molecules. It can effectively reduce the sliding resistance between cement particles, thereby further improving the fluidity of concrete.

3. Steric hindrance

The polycarboxylate concrete superplasticizer has hydrophilic branched chains in its structure, which stretch in the aqueous solution and can form a hydrophilic three-dimensional adsorption layer with a certain thickness on the surface of the adsorbed cement particles. When the cement particles are very close to each other, the adsorption layer rises and overlaps, that is, the more the steric hindrance overlaps between the cement particles, the greater the steric repulsion, and the greater the obstruction to the cohesion between the slush particles. The settling drop remained good.

4. Sustained release effect of graft copolymer branch chain

During the preparation process of polycarboxylate superplasticizer liquid, some branched chains will be attached to the superplasticizer molecules. These branched chains can not only provide steric hindrance effect, but also in the high alkalinity environment of cement hydration, these branches will The chain can be gradually cut to release the polycarboxylic acid with dispersing effect, which can improve the dispersion effect of cement particles and control the slump loss.

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