Post Date:2,Mar,2026

Water-reducing agents are commonly used chemical additives in concrete, used to reduce the amount of water added during mixing while maintaining or improving the workability, strength, and durability of the concrete.

Water-reducing agents can be classified according to their chemical composition and properties as follows:

1. Classification by Water Reduction Rate: Ordinary water-reducing agents: Water reduction rate is approximately 5%-10%, such as lignin sulfonates. High-efficiency water-reducing agents: Water reduction rate is approximately 10%-20%, such as naphthalene-based and melamine-based water-reducing agents. High-performance water-reducing agents: Water reduction rate exceeds 20%, such as polycarboxylate-based water-reducing agents.

2. Classification by Chemical Composition: Lignosulfonate water-reducing agents: Raw materials are derived from wood and papermaking wastewater; they are low-cost, but their water-reducing effect is generally moderate, and they are commonly used in ordinary concrete. Naphthalene-based water-reducing agents: Made from naphthalene, they have a high water reduction rate and are suitable for high-strength concrete. Melamine-based water-reducing agents: Made from melamine, they have a high water reduction rate and early strength effect. Polycarboxylate superplasticizers: A new generation of high-performance superplasticizers with high water reduction rate and good environmental performance, suitable for high-strength, self-compacting concrete.

3. Classification by Function: Ordinary superplasticizers: Only have water reduction function. Retarding superplasticizers: Combine water reduction and delaying concrete setting time. Accelerating superplasticizers: Combine water reduction and shortening time, improving early concrete strength. Air-entraining superplasticizers: Combine water reduction and introducing micro-air bubbles, improving the frost resistance of concrete.

Mechanism of Action of Superplasticizers: The mechanism of action of superplasticizers is mainly based on their molecular structure and physicochemical behavior in the cement-water system.

1. Adsorption: The hydrophilic groups in the superplasticizer molecule bind to water molecules, while the hydrophobic groups adsorb onto the surface of cement particles. This adsorption causes the superplasticizer molecules to form a monomolecular film on the surface of cement particles, changing the surface properties of the cement particles.

2. Dispersion: Cement particles in water usually agglomerate due to van der Waals forces, forming a flocculated structure that encapsulates a large amount of free water. After water-reducing agent molecules adsorb onto the surface of cement particles, the negatively charged hydrophilic groups create electrostatic repulsion between the particles, causing them to disperse. This dispersion releases the trapped free water, increasing the fluidity of the concrete.

3. Lubrication: Water-reducing agent molecules form a lubricating film on the surface of cement particles, reducing frictional resistance between particles. This lubrication further improves the fluidity and workability of the concrete.

4. Reduced Surface Tension: Water-reducing agents lower the surface tension of water, allowing it to penetrate more easily between cement particles, thus improving the uniformity and workability of the concrete.

5. Reduced Water-Cement Ratio: While maintaining the same fluidity, water-reducing agents can reduce the amount of water used, thereby lowering the water-cement ratio and improving the strength and durability of the concrete.