POROSIFYING, SOLIDIFICATION-ACCELERATING ADDITIVE FOR BINDING AGENT BUILDING MATERIALS, AND PROCESS OF PRODUCING SAME

The invention relates to a porosifying, solidification- accelerating additive for binding agent building materials, consisting of Al2O3 50 - 90 % MgO 4 - 20 % SiO2 0.5 - 15 % AlN 0.1 - 5 % Fe2O3 0.1 - 5 % CaO 0.1 - 5 % F 0.1 - 5 % Na2O 0.1 - 5 % K2O 0.1 - 2 % as well as in the form of metallic particles Al 0.1 - 10 % Si 0.1 - 3 % Fe 0.1 - 3 % balance in total up to 5 % annealing losses 0.1 - 15 % and of mineral main constituents in the form of corumdum (.alpha.-Al2O3) and spinel (MgO x Al2O3), wherein the metallic aluminium particles are enveloped by mineral transition modifications from aluminium hydroxide (Al2O3 x 3H2O) to .alpha.-aluminium oxide, wherein the powder comprises a particle size of at least 90% smaller than 500 .mu.m and wherein the BET surface of the powder amounts to at least 10 m2/g. Furthermore, the invention relates to a process of producing a porosifying, solidification-accelerating additive for a binding agent building material by thermally treating the powder in a flue gas flow down to a residual moisture of 2 % maximum by shock drying at flue gas temperatures of 400 to 500 ÀC in a drying time of less than 10 seconds, and by thermally activating the powder by partially calcinating same within a temperature range of 400 to 1,000 .degree.C, wherein the holding time is calculated in such a way that there is obtained a BET surface of the activated powder of at least 10 m2/g, and wherein the metallic aluminium particles are enveloped by mineral transition modifications from aluminium hydroxide (A1203 x 3H2) to a-aluminium oxide.