Abstract: To prevent the escape of water into the porous aggregate of light-weight concrete at the time of pumping, the individual particles of the additive, which, with cement slurry, forms a gel-like protective layer, which is scarcely permeable to water, for a period of time, and which facilitates a bond between the aggregate and the cement. The protective layer can be produced by spraying a solution, in particular an aqueous solution of the additive into the aggregate particles, which are heated to a temperature above the boiling point of the solvent, and by evaporating the solvent.