Introduction. In the past, air and hydraulic lime were primary materials in building constructions. Due to the limited production of hydraulic lime in Russia, it is of interest to study the possibility of replacing natural hydraulic lime NHL in plaster mortars with artificial hydraulic lime HL, which is not inferior in its properties to natural NHL. Materials and methods. Artificial hydraulic lime HL was obtained by mixing air lime with a pozzolan additive. Diatomite from the Inzenskoye deposit, condensed, uncompacted microsilicon MK-85, and highly active metakaolin VMK-45 were used as pozzolan additives in the work. Results. It has been established that the most effective pozzolan supplement is metakaolin. The introduction of metakaolin into a lime binder in an amount of 10-50% by weight entails an increase in the compressive strength of the solution samples at the age of 28 days by 2.8-12.83 times compared with the sample without the additive. The highest strength value is achieved when 50% metakaolin is added to lime to the binder - after 28 days of hardening, the strength is 1.01 MPa. Conclusion. It has been established that the use of metakaolin in the amount of 40-50% of the mass of air lime makes it possible to obtain artificial hydraulic lime. The developed compositions of artificial hydraulic lime are proposed to be used for the restoration of buildings of historical buildings, as well as the finishing of newly erected facilities.