Industrial Citric Acid in Joint Gypsum

Main Function of Industrial Citric Acid in Joint Gypsum

The main function of industrial citric acid in joint gypsum is as a retarder, which reacts with calcium ions on the surface of gypsum to form stable calcium citrate complexes, thereby delaying the setting rate of gypsum. ‌


Industrial citric acid, as an organic acid retarder, has three carboxyl groups and one hydroxyl group. 

These functional groups enable it to undergo complexation reactions with calcium ions on the surface of gypsum, generating insoluble calcium citrate precipitate on the surface of hemihydrate gypsum. This precipitation not only prevents the contact between hemihydrate gypsum and dihydrate gypsum crystals, promoting the growth of single crystals, but also prolongs the formation time of crystal nuclei, greatly delaying the formation and hardening process of hydration products. In addition, citric acid, as an effective chelating agent, can form a hexagonal cyclic chelate with calcium ions in solution, reducing the concentration of calcium ions in the solution and further prolonging the formation time of Y-water gypsum embryos, thereby significantly delaying the hardening process of gypsum. ‌


This retarding effect is particularly important for the preparation of gypsum building materials such as joint gypsum, as it can help control the setting speed of gypsum, thereby improving its construction performance and usability. By adjusting the dosage of citric acid, effective control of the strength of gypsum hardened body can be achieved, which not only ensures the construction convenience of gypsum building materials, but also meets the requirements of their strength and durability.