The use of block copolymers which were prepared by polymerization of a poly(alkylene oxide) compound (A) with at least one ethylenically unsaturated monomer compound (B), as dispersants for aqueous suspensions of solids, in particular based on hydraulic binders, such as, for example, cement, lime, gypsum or anhydrite, is described. Surprisingly, these block copolymers have a substantially better water-reducing power at the same dose in comparison with conventional superplasticizers based on comb polymers. Moreover, the slump loss can also be reduced in comparison with conventional superplasticizers by modification of the adhesive block.