Water retaining agents are divided into four categories:

① Cellulose water retainers

The most widely used in the market is hydroxypropyl methylcellulose. The second is methylcellulose. The third is carboxymethyl cellulose. The comprehensive performance of hydroxypropyl methylcellulose is better than that of methylcellulose. The water retention of both is much higher than that of carboxymethyl cellulose. But the thickening and bonding effects are worse than those of carboxymethyl cellulose.
In gypsum dry mixed building materials, the dosage of hydroxypropyl and methylcellulose is generally 0.1% to 0.3%. The dosage of carboxymethyl cellulose is 0.5% to 1.0%. A large number of application examples have proved that the combined use of the two has a better effect.

② Starch water retainers

Starch water retainers are mainly used for gypsum putty and surface type plaster, and can replace part or all of the cellulose water retainers. Add starch water retainers to gypsum dry powder building materials. It can improve the workability, construction performance, consistency, etc. of the slurry.
Common starch water retainer products include cassava starch, pregelatinized starch, carboxymethyl starch, carboxypropyl starch, etc. The dosage of starch water retaining agent is generally 0.3% to 1%. If the dosage is too large, gypsum products will mildew in a humid environment, which will directly affect the quality of the project.

③ Glue water retaining agent

Some instant adhesives can also play a good auxiliary role in water retention. For example, 17-88, 24-88 polyvinyl alcohol powder, Tianqing gum and guar gum are used in gypsum dry mixed building materials such as bonding gypsum, gypsum putty, and gypsum insulation adhesive.
Under a certain dosage, the dosage of cellulose water retaining agent can be reduced. Especially in fast-adhesive gypsum. In some cases, it can completely replace cellulose ether water retaining agent.

④ Inorganic water retaining material

Combined with other water retaining materials for use in gypsum dry mixed building materials. It can reduce the dosage of other water retaining materials. Reduce product costs. It also plays a certain role in improving the workability and construction properties of gypsum slurry. Commonly used inorganic water retaining materials include bentonite, kaolin, diatomaceous earth, zeolite powder, perlite powder, attapulgite clay, etc.
That is the classification of water retaining agents.