Mechanism of action:
After the cement is mixed with water, due to the hydration of the cement particles, the surface of the cement particles forms an electric double layer structure to form a solvated water film, and the surface of the cement particles has an opposite charge to cause the association between the cement particles , So that the cement slurry forms a flocculating structure, so that 10% to 30% of the mixing water is wrapped in the cement particles, which cannot participate in free flow and lubrication, thereby affecting the fluidity of the concrete mixture.
When the water-reducing agent is added, because the water-reducing agent molecules can be adsorbed on the surface of the cement particles, the surface of the cement particles is charged with the same electric charge (usually negative), which forms an electrostatic repulsion effect, which promotes the mutual dispersion of the cement particles and the disintegration of the flocculation structure. , It releases part of the water that is wrapped and participates in the flow, thereby effectively increasing the fluidity of the concrete mixture.
The hydrophilic group in the water-reducing agent is very polar, so the water-reducing agent adsorption film on the surface of the cement particles can form a stable solvated water film with water molecules. This water film has a good lubricating effect. , Can effectively reduce the sliding resistance between cement particles, thereby further improving the fluidity of concrete.
the hydrophilic branch in the structure of the water reducer stretches in the aqueous solution to form a hydrophilic three-dimensional adsorption layer with a certain thickness on the surface of the adsorbed cement particles. When the cement particles approach, the adsorption layer starts to overlap, that is, steric hindrance is generated between the cement particles. The more overlap, the greater the steric hindrance repulsion, and the greater the obstacle to the cohesion between the cement particles, which makes the concrete slump. The degree is maintained well.
The slow-release effect of graft copolymerization branched chain:
During the preparation process of new water reducing agent such as polycarboxylic acid water reducing agent, some branches are grafted on the molecule of the water reducing agent, and the branching chain can not only provide space In addition, in the high alkalinity environment of cement hydration, the branch chain can be slowly cut to release polycarboxylic acid with dispersing effect, which can improve the dispersion effect of cement particles and control slump. Falling loss.