Cement, Water-Repellent

a hydraulic binding material, obtained by mixing finely ground cement clinker with gypsum and hydrophobizing additives (mixed water-insoluble naphthenic acids, naphthenate soap, oleic acid, oxidized petrolatum, synthetic fatty-acid still residues, and other substances). The additive, 0.1-0.3 percent of the volume of the cement, forms on the surface of the cement a hyperthin (monomolecular) water-repellent film, minimizing the hygroscopicity of the cement and hence protecting it from damage even under prolonged periods of heightened moisture conditions. Concretes and solutions based on water-repellent cement are marked by lower water absorption, greater frost resistance, and greater imperviousness to water than ordinary cement. Besides portland cement, cinder, alumina, and other kinds of cement can also be made water-repellent.