Fluoride-borate mixtures as a foaming intensifier for TPP slag wastes

Introduction. The possibility of intensifying the foaming process of thermal power plant (TPP) slag waste by introducing a mixture of fluxes consisting of sodium tetraborate (Na 2 B 4 O 7 ) and sodium fluoride (NaF) was studied. The relevance of the study is due to the need for efficient recycling of industrial waste and the production of building materials with improved characteristics based on them. The scientific novelty of the work lies in the study of the combined effect of these fluxes on the foaming processes and the formation of the porous structure of the material. The purpose of the study is to optimize the composition of the fluxing mixture to reduce the melting point and improve the quality of porous silicate materials. Materials and methods. The methods of X-ray phase analysis (XRD), infrared spectroscopy (FTIR), microscopic analysis and experimental determination of the density of specimens were used. Results. A study of changes in the temperature modes of sintering and foaming with the combined introduction of Na 2 B 4 O 7 and NaF mixtures was performed, as well as their effect on the structural and phase characteristics of the materials. It was shown that sodium tetraborate promotes uniform distribution of pores and formation of amorphous glass phase. Fluoride causes intensive melting of the structure at elevated temperatures, as well as recrystallization of the melt with formation of albite crystals. The optimal ratio of fluxes was revealed, providing minimum density, stable porous structure and formation of glass-crystalline framework, which contributes to increased strength. Conclusions. The obtained results demonstrate the prospects of the method of recycling slag waste of thermal power plants for obtaining porous building materials using the “self-foaming” technology. Further research can be aimed at optimizing fluxing mixtures and studying the methods of activating ash and slag waste to improve the technological characteristics of the resulting products.