Copolymers which are obtained by free radical copolymerization of a vinylic poly(alkylene oxide) compound (A) with an ethylenically unsaturated monomer compound (B), and the use thereof as dispersants for aqueous solid suspensions, in particular hydraulic binders based on cement, lime, gypsum and anhydrite, are described. With very good water reduction power, the copolymers according to the invention scarcely retard the hardening of the concrete and ensure long processability of the concrete.