Introduction. The purpose of the article is to expand the range of compositions for special structures, which will allow them to be operated in extreme conditions. To achieve this goal, a number of tasks have been solved containing ways to improve the efficiency of composites, incl. low-permeability ones.
 
 Materials and methods. The research methodology includes a system of transdisciplinary approaches that evaluate the composite as a complex system, taking into account the provisions of geomimetics, such as the law of similarity, the law of affinity of structures, technogenic metasomatism, and micromechanics of composite media.
 
 Results. A wide range of cement concretes has been created for unique objects: low-permeability (for protective objects, reservoirs and hydraulic structures). The developed composites have the following performance characteristics (the results for the control sample are given in parentheses): water absorption by weight — 2.5 % (6.1 %), waterproof grade — W14 (W10), air permeability — 0.0253 cm3/s (0.0565 cm3/s), vapor permeability — 0.0021 mg/(m-h-Pa) (0.0030 mg/(m-h-Pa)), effective diffusion coefficient — 1.34 · 10–4 cm2/s (1.56 · 10–4 cm2/s).
 
 Conclusions. The similarity in the work of the components of different composite binders, incl. During the two-stage hydration of clinker minerals, in particular, in the first phase, the formation of low-density compounds of different phases occurs, and in the second phase, the binding of calcium hydroxide to low-basic crystalline hydrates occurs. The increase in the activity of the composite binder is due to the synergistic effect of a number of reasons: amorphous silica-containing components bind Ca(OH)2, released during the hydration of clinker minerals, in the second generation CSH(I); limestone particles clog the pores, compacting the structure; and fly ash microspheres are centers of crystallization of new growths.