AbstractMan-made products containing 95…96% of amorphous nanostructured silica were studied for the purpose of their usage as modifiers for cement mortars. These products are “belaya sazha (carbon white)” BS120 (BS) obtained by means of hydrochemical synthesis and amorphous silicon dioxide (ADK) produced from rice husk being thermally treated at 800 оС. Morphological properties and pozzolanic activity of the modifiers were analyzed. Nanostructured material BS is formed from corpuscular nanoscaled particles that are merged into aggregates. Lamellar and flaky ADK particles consist of coalesced nanoscaled granules.The authors explain improving the performance properties of nanomodified cement mortars: increase of durability, water resistance and adhesion indices, reduction of water adsorption and decrease of shrinkage deformation while hardening. Development of mortar formula for waterproofing work is the practical application of the research findings.