Additive for hydraulic compositions

The present invention includes at least one salt of a monovalent metal cation or a polyvalent metal cation, and at least one compound capable of releasing an anion which forms the metal cations and a low solubility salt, at least one polymer containing colloidally dispersed preparations of the type of sulfonated dispersants, it relates to an additive for hydraulic compositions. Said additives are particularly suitable as slump retention agent.