The action mechanism of water reducing agent:
(1) Refining effect: After the concrete is mixed with water, because The hydration effect of concrete particles, the concrete particles produce a double electric layer structure, causing it to form a petroleum etherified water film, and the surface of the concrete particles contains male and female charges, which causes an association effect between the concrete particles, causing the cement mortar to form a flocculation structure. 10% to 30% of the mixing water is encapsulated in the concrete particles and cannot participate in free movement and lubrication, thus affecting the fluidity of the concrete mixture.
When a water-reducing agent is added, the ions of the water-reducing agent can be directionally adsorbed on the surface of the concrete particles, so that the surface of the concrete particles contains the same charge (usually negative). Electric charge), resulting in induced electric friction, promoting the concrete particles to refine each other, the flocculation structure to collapse, releasing the encapsulated water, participating in swimming, thereby effectively improving the fluidity of the concrete mixture.
(2) Lubricating effect: The hydrophilic group in the water-reducing agent has strong chemical properties, so the water-reducing agent adsorption film on the surface of the concrete particles can interact with Oxygen molecules form a stable layer of petroleum etherified water film. This water film has a very good lubrication effect and can effectively reduce the drag pressure between concrete particles, thus improving the overall fluidity of concrete.
(3) Steric hindrance function: The hydrophilic branched chain in the superplasticizer structure flexes and stretches in the saturated solution, thereby absorbing the adsorbed water. There is a certain thickness of hydrophilic vertical adsorption layer formed on the surface of concrete particles. When the concrete particles are close to each other, the adsorption layers begin to overlap, that is, a steric hindrance effect is formed between the concrete particles. The greater the overlap, the greater the steric repulsive force, and the greater the obstruction to the excitation effect between concrete particles, causing the concrete to The slump remains stable.
(4) The sustained-release effect of graft copolymer branched chains: New water-reducing agents such as polycarboxylate water-reducing agents are produced during the preparation process. The ions of the water-reducing agent are grafted with certain branch chains, which not only provide steric hindrance, but also can be gradually broken in the high alkalinity environment of concrete hydration. This in turn emits polycarboxylic acids with refining properties, which can enhance the refining properties of concrete objects and control slump damage.
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