Additive for hydraulically setting compositions

Additive for hydraulically setting compositions, comprising an aqueous, colloidally disperse preparation of at least one salt of a polyvalent metal cation and of at least one polymeric dispersant which comprises anionic and/or anionogenic groups and polyether side chains,

• where the polyvalent metal cation is selected from Al3+, Fe3+, Fe2+, Zn2+, Mn2+, Cu2+, Mg2+, Ca2+, Sr2+, Ba2+ and mixtures thereof, and where the metal cation is present in a quantity such that the following ratio (a) is greater than 1 and less than 30:
• 1
• <
• Σ
• i
• ⁢
• z
• K
• ,
• i
• *
• n
• K
• ,
• i
• Σ
• j
• ⁢
• z
• S
• ,
• j
• *
• n
• S
• ,
• j
• <
• 30
• (
• a
• )
• where
• zK,i is the amount of the charge number of the polyvalent metal cation,
• nK,i is the number of mols of weighed-in polyvalent metal cation,
• zS,j is the amount of the charge number of the anionic and anionogenic groups present in the polymeric dispersant,
• nS,j is the number of mols of the anionic and anionogenic groups present in weighed-in polymeric dispersant,
• the indices i and j are independent of one another and are an integer greater than 0, where i is the number of different kinds of polyvalent metal cations and j is the number of different kinds of anionic and anionogenic groups present in the polymeric dispersant.