Abstract: The present invention relates to an additive which is added in order to reinforce cement. The additive comprises chlorides of alkali metals, alkaline earth metals and/or transition metals and oxides selected from the group consisting of alkali metal and alkaline earth metal oxides, aluminum oxide, silica, apatite and/or zeolites and comprises, in particular, a combination of sodium chloride, ammonium chloride, aluminum chloride, potassium chloride, calcium chloride, magnesium chloride, magnesium oxide, magnesium sulfate, sodium carbonate, silica, apatite and/or zeolites. Additives of this type can be used, inter alia, to stabilize/modify cement; consolidate sand and/or soil, such as when building roads, dykes, tunnels, foundations and the like, immobilize pollutants, during the injection of cement compositions, such as grouting, and for the production of concrete.