FIELD: manufacture of building materials. SUBSTANCE: additive contains alkaline component: alkali metal carbonates, bicarbonates, and silicates; acidic component: aluminum, ferric, and ferrous sulfates, and alum; water-retaining organic component selected from (i) water-soluble cellulose polyesters and/or its derivatives, (ii) polyvinyl alcohol and/or its polyethers, or its partial alkali hydrolysis products, (iii) poly(vinylsulfonic acid) and/or its salts, and/or its alkali saponification products, and (iv) mixtures of compounds of the indicated groups; and complexing component: aromatic acids and/or alcohols, wherein weight ratio of the two last and sum of the two first components varies between about 0.05:0.02:1 and about 0.5: 0.4: 1. Weight ratio of above-defined additive and clinker component of Portland cement in hardening cement-water systems varies between about 0.002:1 and 0.03: 1. Before being added, additive is preliminarily homogenized with indicated hydraulic binder until complex formation starts to be visually and instrumentally observed. EFFECT: improved quality and longevity of building objects, including those in the area of geotechnic building, as well as quality of repair and restoration operations without special additional expenses. 8 cl, 2 tbl
