Polycarboxylate water-reducing agent is a new type of high-efficiency concrete water-reducing agent developed in the mid-1980s. It was first successfully developed in Japan. Polycarboxylic acid water-reducing agent can significantly improve the fluidity and durability of concrete. Therefore, in recent years, it has become a focus of attention in the concrete engineering and materials circles in many countries in the world. Polycarboxylic acid water reducer is also recognized in the world as the water reducer with the best research and application prospects and the best comprehensive performance. The mechanism of action is briefly described as follows:
After the cement is mixed with water, due to the molecular gravity of the cement particles, the cement slurry forms a flocculation structure, so that 10-30% of the mixing water is wrapped in the cement particles and cannot participate in free flow and lubrication, thereby affecting Improve the fluidity of the concrete mixture. When the polycarboxylic acid water-reducing agent is added, because the polycarboxylic acid water-reducing agent molecules can be adsorbed on the surface of the cement particles, the surface of the cement particles is charged with the same electric charge (usually negative charge), forming an electrostatic repulsion effect, making the cement The particles disperse each other, destroy the flocculation structure, release the encapsulated water, and participate in the flow, thereby effectively increasing the fluidity of the concrete mixture.
The hydrophilic group in the polycarboxylate water reducer is very polar, so the polycarboxylate water reducer adsorption film on the surface of the cement particles can form a stable solvated water film with water molecules. This water film It has a good lubricating effect and can effectively reduce the sliding resistance between cement particles, thereby further improving the fluidity of concrete.
3. Spatial hindrance:
The structure of polycarboxylic acid water reducer has hydrophilic branches, which stretch in the aqueous solution to form a hydrophilic three-dimensional adsorption layer with a certain thickness on the surface of the adsorbed cement particles. When the cement particles are close to each other, the adsorption layer begins to overlap, that is, steric hindrance is generated between the cement particles. The more overlap, the greater the steric hindrance repulsion and the greater the obstacle to the cohesion between the cement particles, which makes the concrete collapse. The fall is well maintained.