The most widely used types of water-reducing agents at present are lignin-based water-reducing agents, naphthalene-based water-reducing agents, melamine-based high-efficiency water-reducing agents, and polycarboxylate-based high-efficiency water-reducing agents. Their respective characteristics are as follows:
1) Lignin-based water-reducing agent
The main component of lignin-based water-reducing agent is lignin sulfonate, including lignocalcium, lignin sodium and lignin magnesium. It is an ordinary water reducing agent. Its water reduction rate is not high, and it also retards condensation and entrains air. Therefore, it is necessary to control the appropriate dosage when using it. Otherwise, excessive dosage will cause a decrease in strength and is uneconomical. It may even not condense for a long time, causing engineering accidents.
2) Naphthalene-based high-efficiency water-reducing agent
Naphthalene-based, methylnaphthalene-based, anthracene-based, coumaron-based, and coal-tar mixture water-reducing agents are produced as raw materials They all come from different fractions of coal tar, so they are collectively called coal tar water-reducing agents. This type of water reducing agent is a polymer electrolyte containing monocyclic, polycyclic or heterocyclic aromatic hydrocarbons with polar sulfonic acid groups, with a relative molecular mass in the range of 1,500 to 10,000. Because the sulfonic acid group has good dispersion in cement, that is, the water-reducing rate is high, coal tar-based water-reducing agents belong to the category of high-efficiency water-reducing agents. They do not retard setting or entrain air within the appropriate molecular weight range. Since the production process of naphthalene-based water-reducing agents is mature, the supply of raw materials is stable, and the output is large and the application is convenient, it gradually takes advantage. Therefore, usually coal tar-based water-reducing agents mainly refer to naphthalene-based water-reducing agents. After spray drying, naphthalene series high-efficiency water reducing agent can be used as a leveling agent for grouting materials.
The appropriate dosage is generally 0.2%~1.0% of the cement mass.
3) Melamine-based high-efficiency water-reducing agent
Melamine-based high-efficiency water-reducing agent (commonly known as melamine water-reducing agent), the chemical name is sulfonated melamine formaldehyde resin, its performance is similar to that of naphthalene They are similar to water reducing agents, both are non-air-entraining and have no retarding effect. Its water-reducing enhancement effect is slightly better than that of naphthalene-based water-reducing agents, but the dosage and price are also slightly higher than that of naphthalene-based water-reducing agents.
The appropriate dosage is generally 0.05~1.0% of the cement mass.
4) Polycarboxylate-based high-efficiency water-reducing admixture
Polycarboxylate-based high-efficiency water-reducing admixture is developed and developed with the development and application of performance concrete. A new type of high-performance concrete water-reducing agent, which has excellent properties such as high strength, heat resistance, durability, and weather resistance. The use of polycarboxylate-based high-efficiency water-reducing admixtures in dry-mixed mortars is still in its infancy.
The appropriate dosage is 0.05%~1.0% of the general cement mass. </p
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