FIELD: manufacture of building materials. SUBSTANCE: expansion additive based on sulfoaluminate clinker for manufacturing nonshrinking or expanding products when added to hydraulic binder, which includes Portland cement and/or its modifications, comprise sulfoaluminate clinker composed, wt %: low- basicity calcium sulfoaluminate (4CaO•3Al2O3•SO3) 20-65, high-basicity calcium sulfoaluminate ((7-9)CaO•(2-3)Al2O3•2SO3,) 15-30, dicalcium silicate ((1,8-2,3)CaO•SiO2,) 0.5-55, monocalcium aluminate (CaO•Al2O3) 1-5, anhydrite (CaSO4) 3- 10, impurities - the balance, and, additionally, an aromatic acid (in particular benzoic acid) and a higher fatty acid at weight ratio of indicated mineral components to acids 1:(0.025-0.3):(0.02-0.2), said higher fatty acid being stearic or oleic acid, or their 1:5 to 5:1 w/w mixtures. Acids contained in expansion additive are present in the form of solutions and/or melts. Hydraulic binder is a product of joint or separate (with subsequent mixing) grinding of matrix ingredient and expansion additive, said matrix ingredient being Portland cement and/or its modifications: products of joint or separate (with subsequent mixing) grinding of Portland cement clinker and gypsum stone at weight ratio of Portland cement clinker, gypsum stone (calculated for SO3), and expansion additive 100:(2-4):(1.5-4). Sulfoaluminate clinker is fired to caking in reductive medium at temperatures allowing content of tricalcium silicate 0.5-3% and that of content of mayenite and/or its halide or sulfide derivatives 0.3-2%. Grinding is effected until homogenously distributed waterproofed film of expanding phase appears on binder particles when being formed. The latter is determined with regard to criterion of formation after tempering of resulting product with water of globular mass homogenized by stirring and rubbing to give homogenous binding water suspension. EFFECT: reduced expenses and increased storage time of nonshrinking or expanding Portland cement. 7 cl, 3 tbl, 3 ex
