of the powder form hydraulically setting mixtures for example by injection spraying with or without pressure and the like if they are liquid at ambient temperature as is preferably the case there is no need to heat them before mixing at all events however it is important to ensure that the block copolymers to be used in accordance with the invention are uniformly mixed with the powder form mixtures it is of particular advantage to use the ethylene oxide propylene oxide block copolymers mentioned above in hydraulically setting mixtures particularly primers having the following composition ______________________________________15 to 60 parts by weight high alumina cement 0 to 25 parts by weight gypsum more particularly in the form of gypsum semihydrate 0 to 70 parts by weight portland cement 20 to 80 parts by weight quartz sand 0 to 30 parts by weight fillers particularly calcium carbonate 0 to 6 parts by weight casein and or vegetable proteins 0 to 16 parts by weight redispersion powder and0 to 3 parts by weight typical additives such as plasti cizers accelerators retarders and or other auxiliaries ______________________________________ the present invention also relates to hydraulically setting mixtures more particularly cement based primers containing ethylene oxide propylene oxide block copolymers having the features mentioned above these mixtures are distinguished from mixtures which do not contain the block copolymers in question above all by the following advantageous properties ______________________________________portland cement 35 f 38 by weighthigh alumina cement 12 by weightquartz sand particle size 30 5 by weight0 to 0 3 mm limestone powder 9 by weightslaked lime 6 by weightcasein 3 5 by weighturea 0 5 by weightstucco 0 5 by weightsoda 0 05 by weightfoam.