Here is the performances of superplasticizer in concrete as following:
(1) Dispersion: After the cement is mixed with water, due to the hydration of the cement particles, the cement particles show the formation of an electric double layer structure, which forms a solvated water film, and the surface of the cement particles has a heterogeneous charge that causes the cement particles to produce The association makes the cement slurry form a flocculation structure, so that 10% to 30% of the mixing water is encapsulated in the cement particles and cannot participate in the free flow and the lubricating effect, thus affecting the fluidity of the concrete mixture.
When the water reducer is added, the water reducer molecules can be adsorbed on the surface of the cement particles, so that the surface of the cement particles has the same charge (usually negative charge), which forms an electrostatic repulsion, which promotes the dispersion of the cement particles and the disintegration of the flocculation structure. , Release part of the wrapped water, participate in the flow, thereby effectively increasing the fluidity of the concrete mixture.
(2) Lubricating effect: 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 the water molecules. This layer of water film has a good The lubricating effect can effectively reduce the sliding resistance between cement particles, thereby further improving the fluidity of concrete.
(3) Steric steric hindrance: The water-reducing agent structure has hydrophilic branches that extend into the aqueous solution, thereby 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, the adsorption layer starts to overlap, that is, steric hindrance occurs between the cement particles. The more overlap, the greater the steric repulsive force, the greater the resistance to the aggregation of the cement particles, and the concrete collapse The degree remains good.
(4) Slow-release effect of graft copolymerization branch: new water reducer such as polycarboxylic acid water reducer, in the preparation process, some branches are grafted on the molecule of water reducer, the branch can not only Provides a steric hindrance effect, and in the high alkalinity environment of cement hydration, the branch chain can also be slowly cut off, thereby releasing a polycarboxylic acid with a dispersing effect, which can improve the dispersion effect of cement particles, And control slump loss.