Rendering building materials hydrophobic

Claim 1

A process for simultaneously cleaning and rendering a preformed building material hydrophobic, which comprises (1) applying to the surface of the building material selected from the group consisting of concrete, bricks, glazed ceramic tiles and plaster, a composition consisting essentially of a hydrophobic agent selected from the group consisting of organopolysiloxanes having siloxane units of the general formula R n H m SiO.sub.(4-m-n)/2, silanes of the formula R n SiX 4-n and partial hydrolysates thereof, alkali metal hydrocarbon siliconates of the formula R'Si(OH) 2 OM and polymers having units of the formula R'SiO(OM) and mixtures thereof, wherein R is selected from the group consisting of alkyl and aryl radicals having up to 18 carbon atoms, R' is selected from the group consisting of a monovalent hydrocarbon radical having up to 5 carbon atoms and a phenyl radical, M represents an alkali metal atom, X represents a hydrolyzable radical, n denotes 0, 1, 2, or 3 and m denotes 0 or 1, and in the polysiloxane the average value of the n is from 0.9 to 1.8, and n is 1 in at least 50 percent of the number of siloxane units, a solvent for the hydrophobic agent in which the hydrophobic agent is present in an amount of from 0.2 to 50 percent by weight based on the weight of the hydrophobic agent and solvent and a residue forming filler having a surface area of at least 50 m 2 /g, in an amount of from 1 to 25 percent by weight based on the total weight of the hydrophobic agent and solvent, (2) removing the solvent by evaporation to form a filler residue on the surface of said building material and thereafter (3) removing the filler residue from said surface to simultaneously clean and render said building material hydrophobic.