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Action mechanism of water reducing agent in concrete 2022-06-20 10:49:38

Under the same condition of concrete slump, the admixture which can reduce mixing water can be divided into ordinary water reducing agent, high efficiency water reducing agent and high performance water reducing agent according to the size of water reducing rate.The specific action mechanism is as follows:

1.Dispersion

Cement and water mix, due to the hydration of cement particles, cement particles that form the structure of electric double layer, form solvation water film, and the cement particle surface with opposite charges make cement particle between associating with cooperation, to form slurry flocculation structure, make the 10% ~ 30% of the mixing water is wrapped in cement particles, can't participate in free flow and lubrication, Thus affecting the fluidity of concrete .

When adding water reducing agent, because the water reducing agent molecules adsorbed on the surface of cement particles can redirect, cement particle surface (usually a negative charge) with the same charge, form the electrostatic repulsion, prompted the cement particles disperse mutually, flocculation structure collapse, release the wrapped part of the water, participate in the flow, so as to effectively increase the liquidity of concrete.

2 Lubrication

Water-reducing agent in the hydrophilic base polarity is very strong, so the surface of cement particles of water-reducing agent adsorption film and water molecules can form a stable layer of solvated water film, this layer of water film has good lubrication, can effectively reduce the sliding resistance between cement particles, so as to further improve the fluidity of concrete.

3 Steric hindrance

The hydrophilic branch chain in the structure of the water reducing agent extends in the aqueous solution, thus forming a hydrophilic three-dimensional adsorption layer with a certain thickness on the surface of the cement particles. When the cement particles close, the adsorption layer began to overlap, that is, in the cement particles produce space resistance, the more overlap, space resistance repulsion, the greater the condensation of cement particles hinder the greater, so that the slump of concrete to maintain good.

4 Sustained release of grafted copolymerized branched chains

New type of water reducing agent such as poly (carboxylic acid water reducing agent in the process of preparation, the molecules of water reducing agent on the grafting on some of the branched chain, the branched chain not only can provide space steric effect, and, in the high basicity of cement hydration environment, the branched chain can also slowly is cut off, to release more carboxylic acid with dispersion effect, so that it can improve the effect of the dispersion of cement particles, and control the slump loss.

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