Calcium sulfate composition comprising an additive

A composition comprising, based on the total mass of the composition:

• A) at least 10 wt % of a binder based on calcium sulfate and
• B) 0.005 to 5 wt % of an additive prepared from components comprising:
• i) at least one water-soluble salt of a polyvalent metal cation,
• ii) at least one compound able to release an anion which forms a sparingly soluble salt with the polyvalent metal cation, and
• iii) at least one polymeric dispersant which comprises an anionic and/or anionogenic group, and a polyether side chain,
• wherein the polyvalent metal cation being is at least one selected from the group consisting of Al3+, Fe3+, Fe2+, Cu2+, Mg2+, Ca2+, Sr2+, Ba2+ and mixtures thereof,
• the metal cation is present in an amount such that the relation according to formula (a) is greater than 0.1 and less than or equal to 30:
• 0.1
• <
• Σ
• i
• 
• z
• K
• ,
• i
• 
• n
• K
• ,
• i
• Σ
• j
• 
• z
• s
• ,
• j
• 
• n
• s
• ,
• j
• ≤
• 30.
• (
• a
• )
• 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/or anionogenic group present in the polymeric dispersant,
• nS,j is the number of moles of the anionic and/or anionogenic group present in the polymeric dispersant,
• the indices i and j are independent of one another and are each an integer greater than 0,
• i is the number of different polyvalent metal cations, and
• j is the number of different anionic and/or anionogenic groups present in the polymeric dispersant.