What is the role of water-reducing admixture? In construction, water-reducing admixture is one of the more commonly used admixtures. Its essence is to improve the fluidity of concrete without changing the mix ratio, that is, to improve its plasticity. . Technical staff's interpretation: Water-reducing agents can reduce the amount of mixing water, improve the strength of concrete, and can also save the amount of cement admixtures. Let's take a look at the detailed functions of water-reducing agents.
The dispersion effect of the water reducing agent: After the cement is mixed with water, due to the gravity of the cement particle molecules, the cement slurry forms a flocculation structure, so that 10% to 30% of the mixing water is wrapped in Cement particles cannot participate in free flow and lubrication, thus affecting the fluidity of the concrete mixture. When the water-reducing agent is added, the water-reducing agent molecules can be directionally adsorbed on the surface of the cement particles, so that the surfaces of the cement particles have the same charge (usually negative charge), forming electrostatic repulsion, which promotes the mutual dispersion of the cement particles and the destruction of the flocculation structure. , releasing part of the wrapped water to participate in the flow, thereby effectively increasing the fluidity of the concrete mixture.
The lubrication effect is also one of the functions of water-reducing agents: 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 layer with water molecules. Solved water film, this water film has a good lubrication effect and can effectively reduce the sliding resistance between cement particles, thereby further improving the fluidity of concrete.
Steric hindrance: The hydrophilic polyether side chains in the superplasticizer structure extend in the aqueous solution, thereby forming a certain thickness of hydrophilic three-dimensional adsorption on the surface of the adsorbed cement particles. layer. When the cement particles are close to each other, the adsorption layers begin to overlap, that is, steric hindrance occurs between the cement particles. The more overlap, the greater the steric repulsion, and the greater the obstruction to the cohesion between cement particles, causing the concrete to collapse. The temperature remains good.
Finally, the role of water-reducing agent is the sustained-release effect of the grafted copolymer branch: during the preparation process of new water-reducing agents such as polycarboxylate water-reducing agents, on the molecules of the water-reducing agent Graft some branched chains, which not only provide steric hindrance effect, but also can be slowly cut off in the high alkalinity environment of cement hydration, thereby releasing polycarboxylates with dispersing effect. Acid, thus improving the dispersion of cement particles and controlling slump loss.
The emergence of water-reducing agents has made it easier for many manufacturers to understand the role of water-reducing agents and choose according to their own needs. I believe it will help you.
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