The invention relates to compositions intended to be applied to the surfaces of freshly poured mortars and/or concretes, before the beginning of the setting, in order simultaneously to prevent the evaporation of the water present in said mortars and/or concretes, which is necessary for their setting and then for their hardening, and in order to create, on said treated surfaces, high adhesiveness for the finishing materials intended to cover them, these compositions being provided in the form of aqueous emulsions comprising at least one paraffin wax (a), alone or in combination with at least one hydrocarbon compound (b) and/or with at least one other hydrocarbon compound (c) different from the hydrocarbon compound (b), and also comprising at least one latex (d) formed of a colloidal aqueous emulsion of at least one polymer, and at least one pulverulent inorganic or organic filler (e).