Die Rolle von Polycarboxylat und anderen Fließmitteln in Fugenmaterialien

Polycarboxylate other superplasticizer is an important component of grouting materials. Water reducing agent is the most important quality of grouting materials. It is an additive that can significantly reduce the water content of grouting materials while maintaining the fluidity of grouting materials.

1. Dispersion:

After the cement is mixed with water, due to the effect of the molecular gravity 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 the free flow and lubrication, thus affecting the fluidity of the concrete mixture. After adding water-reducing agent, because the water-reducing agent molecules can be adsorbed on the surface of cement particles, the surface of cement particles has the same electric charge (usually negative electric charge), forming electrostatic repulsion, promoting the mutual dispersion of cement particles, the destruction of flocculation structure, releasing the wrapped water, participating in the flow, thus effectively increasing the fluidity of concrete mixture.

2. Lubrication:

The hydrophilic group polarity in polycarboxylate ether superplasticizer is very strong, so the water-reducing agent adsorption film on the surface of cement particles can form a stable solvated water film with water molecules. This water film has a good lubrication effect, which can effectively reduce the sliding resistance between cement particles, so as to further improve the fluidity of concrete.

3. Slow release effect of graft copolymerization branch chain:

During the preparation of polycarboxylate ether superplasticizer, some branch chains are grafted on the molecules of water-reducing agent. This branch chain can not only provide steric hindrance effect, but also be slowly cut off in the high alkalinity environment of cement hydration, thus releasing the polycarboxylic acid with dispersion effect, which can improve the dispersion effect of cement particles and control the slump loss.

4. Spatial steric effect:

The hydrophilic polyether side chain in the polycarboxylate ether superplasticizer structure extends in the aqueous solution, thus forming a hydrophilic three-dimensional adsorption layer with a certain thickness on the surface of the adsorbed cement particles. When the cement particles are close to each other, the adsorption layer begins to overlap, that is to say, there is a steric resistance between the cement particles. The more the overlap, the greater the steric resistance repulsion, and the greater the resistance to the cohesion between the cement particles, so that the slump of the concrete is kept good.