Additive for hydraulically setting compounds

Additive for hydraulically setting compositions, comprising a colloidally disperse preparation of at least one water-soluble salt of a polyvalent metal cation, at least one compound able to release an anion which forms a sparingly soluble salt with the polyvalent metal cation, and at least one polymeric dispersant which comprises anionic and/or anionogenic groups and polyether side chains,

• the polyvalent metal cation being selected from Al3+, Fe3+, Fe2+, Zn2+, Mn2+, Cu2+, Mg2+, Ca2+, Sr2+, Ba2+ and mixtures thereof,
• the metal cation being present in an amount such that the following relation according to formula (a) is greater than 0 and less than or equal to 1:
• 0
• <
• ∑
• i
• ⁢
• z
• K
• ,
• i
• ×
• n
• K
• ,
• i
• ∑
• j
• ⁢
• z
• s
• ,
• j
• ×
• n
• s
• ,
• j
• ≤
• 1
• (
• a
• )
• and where
• zK,i is the amount of the charge number of the polyvalent metal cation,
• nK,i is the number of moles of the polyvalent metal cation,
• zS,j is the amount of the charge number of the anionic and anionogenic group present in the polymeric dispersant, and
• nS,j is the number of moles of the anionic and anionogenic group present in the 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 polyvalent metal cations and j is the number of different anionic and anionogenic groups present in the polymeric dispersant.