and what are their main functions?

there are many kinds of retarder, including sugar, lignosulfonate, hydroxy acid, inorganic salt and so on. set retarder is an additive that reduces the hydration rate and heat of hydration of cement or gypsum and prolongs the setting time. retarders are classified according to structure:1. sugars: calcium sugar, glucose acid salts, etc.2. citric acid, tartaric…