Mechanical Characteristics of Restoration Solutions When Metacaolines Are Used in Their Compositions

Purpose: To analyze the possibility of using highly active metacaolines in the compositions of gypsum-lime binders for restoration work. To consider the compatibility of the components of restoration solutions based on the reproducibility of their main characteristics, such as mineralogical and chemical composition, physical and mechanical properties and durability. Methods: The work uses physico-chemical research methods, as well as methods of comparative analysis, in accordance with the guidelines of GOST 125-2018 “Gypsum binders. Technical conditions”. Results: It is shown that the introduction of metacaolin into the binder compositions provides an increase in the strength of the binder stone. The optimal amount of metacaolin is 20% in a gypsumlime mixture. It has been experimentally established that an increase in the content of Al2O3 in metacaolin from 39 to 44% leads to an increase in the early compressive strength of a stone made of modified gypsumlime binder. An increase in the content of Al2O3 leads to an increase in strength characteristics. Practical significance: The conducted studies demonstrate that such indicators as the average particle size, specific surface area, have an impact on the hydraulic activity of the pozzolan additive. The quality of highly active metakaolins is directly dependent on the degree of purity of kaolin. However, additives may differ in the mass content of oxides, in particular the content of the main oxides SiO2 and Al2O3. The use of highly active metacaolines in the compositions of gypsum-lime binders makes it possible to restore architectural monuments.