The influence of a number of superplasticizers of various chemical bases on the physical and technical properties of clay soils has been studied. Model soils are considered as clay soils: kaolin clay with kaolinite mineral content up to 95 %, bentonite clay with montmorillonite content up to 70%. The greatest increase in the physical and technical properties of clay soils is achieved when they are modified by a polycarboxylate superplasticizer, which is due to adsorption of polymer molecules on clay minerals even with a negative charge of chips and basal planes. This is explained by the ability of side chains of the polycarboxylate ester, which has a similar composition with polyethylene glycols, to be adsorbed on the aluminosilicate layers of clay minerals by the formation of hydrogen bonds. The interaction of kaolinite and montmorillonite included in kaolin and bentonite clay with a polycarboxylate superplasticizer was studied by infrared spectroscopy. It was found that the additive under study belongs to a type of polycarboxylate superplasticizers modified with organo-silanes. Introduction to kaolin and bentonite clays leads to chemisorption with clay minerals and the formation of organomineral bonds, which leads to an increase in the strength characteristics of clays.