- Time：2024/8/12Posted：SHANDONG KUNDU CHEMICAL CO.,LTD.
Gypsum retarder is a substance that can prolong the hydration time of gypsum from hemihydrate gypsum to dihydrate gypsum, thereby prolonging the setting time of gypsum, which are mainly used in gypsum building materials such as gypsum based plastering, bonding gypsum, gypsum wall putty, gypsum based self leveling mortar and gypsum products.
Compared with ordinary Portland cement, building gypsum has a shorter setting and hardening time. It will harden in a very short time after adding water, and the operating time is short, which cannot meet the needs of construction. Therefore, in the development process of gypsum-based building materials, gypsum retarders are generally added to obtain a more appropriate operating time and improve the construction performance of gypsum-based building materials.
There are 3 main types of gypsum retarder (alkaline phosphates, protein gypsum retarder, organic acids and their soluble salts slow-release agents). The following table shows why protein gypsum retarder is best.
Electron microscope analysis of the retarder dosage, setting time and strength loss rate of the samples Samples Setting time/min Strength loss rate/% Compressive strength loss rate/% Gypsum 23 0 0 Protein retarder, 0.05% 125 13.3 12.7 Citric acid, 0.1% 136 65 55.3 Sodium polyphosphate, 0.2% 138 61.7 58 The experiment shows that protein gypsum retarder has the lowest dosage, long enough setting time so sufficient operation time, smallest impact on strength loss rate and compressive strength loss rate.
