Additive for rheology improvement of inorganic binders

A polycondensate containing

• (I) at least a structural unit, which is an aromatic moiety bearing a polyether side chain comprising alkylene glycol units, with the proviso that the number of ethylene glycol units in the side chain is from 9 to 41 and that the content of ethylene glycol units is higher than 80 mol % with respect to all alkylene glycol units in the polyether side chain,
• (II) at least a structural unit, which is an aromatic moiety bearing at least one phosphoric acid ester group and/or its salt, with the proviso that the molar ratio of (I) to (II) is from 0.3 to 4,
• (III) at least a methylene unit (—CH2—), which is attached to two aromatic structural units Y, where
• aromatic structural units Y, independently of one another, are identical or different and are represented by structural unit (I), structural unit (II) or optionally (IV) aromatic structural units of the polycondensate, which are different from structural unit (I) and structural unit (II) and
• wherein the polycondensation degree of the polycondensate containing the units (I), (II), (III) and optionally (IV) is in the range from 10 to 75.