The mechanism of water reduction is that concrete first is the adsorption and dispersion of water reducer. After the admixture is added, the hydrophobic group of water reducer is directional adsorbed on the surface of cement particles, which is the same charge as the surface of cement. And under the action of isotropic electric repulsion, the floc structure formed by cement at the initial stage of adding water is dispersed and disintegrated, and the encapsulated cement molecules are released to achieve the effect of reducing water. The second is the wetting and lubricating effect of the admixture.
Commonly used water reducers include lignosulfonate water reducer, naphthalene type water reducer, melamine water reducer and polycarboxylate type water reducer, etc.
Under the condition that the concrete slump is basically the same, it can reduce the admixture of mixing water. According to the size of its water reducing rate, it can be divided into ordinary water reducing agent, high efficiency water reducing agent and high performance water reducing agent.
At present, it is generally believed that the water-reducing effect of the water-reducing agent is mainly due to the adsorption, dispersion, and wetting and lubricating effects of the water-reducing agent. In the process of mixing cement with water, because the cement minerals contain components with different charges, the mutual attraction of positive and negative charges will cause the concrete to produce a flocculation structure, and the flocculation structure may also be caused by the thermal movement of cement particles in the solution.
These edges and corners collide and attract each other to form. Since the flocculation structure wraps a part of the mixing water and reduces the fluidity, the effect of the water reducing agent is manifested in the following three aspects.
Now, everyone generally accepts three theories on the mechanism of action of water reducing agents: electrostatic repulsion theory, steric hindrance effect theory, and slow release theory of reactive polymers.
This theory is mainly applicable to polycarboxylate water reducers. When the thickness of the adsorption layer on the surface of cement particles increases, it is conducive to the dispersion of cement particles and the release of free water between cement particles. The presence of a large number of comb-shaped side chains – (CH2-CH2-O) n- in the polymer molecules of polycarboxylic acid-based water reducers makes the molecular structure take on a comb-like shape and adsorbs on the surface of cement particles to form a larger adsorption layer. Its water-reducing effect is mainly caused by the steric hindrance effect caused by the macromolecular chain and its branches. After the more and longer branch chains contained in it are adsorbed on the surface of cement particles, a thicker three-dimensional cladding can be formed on the surface of cement particles, so that the cement can achieve a better and longer-lasting dispersion effect.
PCE is a game-changer in concrete technology and has demonstrated exceptional ability to increase the strength and durability of concrete.
Today, we’re delving into the world of polycarboxylate water reducers – a revolutionary material that is changing the way buildings are constructed.
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