Waterproofing agent based on special montan wax fraction

The method of waterproofing a mineral substrate involves dry grinding the agent with the substrate (especially gypsum hemihydrate or dihydrate) so that the agent is finely distributed over the substrate particle surfaces. The grinding process comprises (a) an initial brief pre-grinding phase at low grinding speed, optionally subdivided into individual steps with stepwise substrate material addition; and (b) a post-grinding phase continued until a particle size of below 0.5 mm is achieved. The combination of grinding duration, the grinding speed and the grinding equipment being selected such that the grinding temperature lies \-20 deg C below the increased melting point of the montan wax fraction used in the waterproofing agent described below. Also claimed is a waterproofing agent based on montan wax, a paraffinic hydrocarbon mixture and optionally a fatty acid, for use in the above method, the novelty being that the montan wax is replaced by a special montan wax fraction with high hydrophobic activity constituents, obtained by a selective solubility process. The agent comprises 40-50% of the special montan wax fraction with an acid number of 5-30 mg KOH/g and an acetone-solubles content of 50-90%, 40-50% paraffin wax with a solidification point of 45-60 deg C and an oil content of 0-25 (preferably 5)% and 0-10% higher fatty acid with a solidification point of 45-55 deg C and an acid number of 150-220 mg KOH/g.