Abstract: The invention relates to a copolymer, said copolymer consisting of, as structural units, (i) 0.1 to 50 mole % of units derived from an ethylenically unsaturated monomer (a) having per one mole thereof 25 to 300 moles of C2-C3 oxyalkylene groups; (ii) 0.1 to 49.9 mole % of units derived from a monomer (b) of an alkyl, alkenyl or hydroxyalkyl ester of an ethylenically unsaturated mono- or di-carboxylic acid; (iii) 0.1 to 90 mole % units derived from a monomer (c) selected from the group consisting of an ethylenically unsaturated monocarboxylic acid, a salt thereof, an ethylenically unsaturated dicarboxylic acid, an anhydride thereof and a salt thereof; (iv) optionally up to 30 mole % of other monomers. Said copolymer can be used as a concrete and/or mortar admixture that allows optimal flow ability and, at the same time, can maintain a specific consistency, fluidity and workability of the concrete independently of the cement type.