The mechanism of action of water reducing agent is that 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 lubrication effect and can effectively reduce the sliding resistance between cement particles, thereby further improving the fluidity of concrete.
Due to the hydration of cement particles, the cement particles form a double electric layer structure, causing them to form a solvated water film, and the opposite charge on the surface of the cement particles causes association between cement particles, making The cement slurry forms a flocculation structure, so that 10% to 30% of the mixing water is wrapped in the cement particles and cannot participate in free flow and lubrication, thus affecting the fluidity of the concrete mixture.
When water-reducing agent is added, since the water-reducing agent molecules can be directionally adsorbed on the surface of the cement particles, the surface of the cement particles carries the same charge (usually negative charge), forming electrostatic repulsion, which promotes the cement to The particles disperse each other, the flocculation structure disintegrates, and part of the wrapped water is released to participate in the flow, thereby effectively increasing the fluidity of the concrete mixture. ?
Extended information
The hydrophilic branched chain in the superplasticizer structure stretches in the aqueous solution, thereby forming a certain thickness of hydrophilic layer on the surface of the adsorbed cement particles. three-dimensional adsorption 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.
During the preparation process of new water-reducing agents such as polycarboxylate water-reducing agents, some branch chains are grafted on the molecules of the water-reducing agent. This branch chain can not only provide steric hindrance effect, but also Moreover, in the high alkalinity environment of cement hydration, the branch chain can be slowly cut off, thereby releasing the dispersing polycarboxylic acid, which can improve the dispersion effect of cement particles and control slump loss. .
Suitable for pumping or normal concrete projects with strength levels of C15~C60 and above. It is especially suitable for formulating concrete projects with high durability, high fluidity, high slump retention, high strength and high requirements on appearance quality. It is extremely beneficial for preparing high-fluidity concrete, self-compacting concrete, and fair-faced concrete.
Ordinary water reducing agents should be used for concrete construction where the daily minimum temperature is above 5℃. High-efficiency water-reducing admixtures are suitable for concrete construction where the daily minimum temperature is above 0°C, and are suitable for preparing high-fluidity concrete, high-strength concrete and steam-cured concrete.