Investigation of the properties of alkaline binding materials with the addition of fine bentonite

Introduction. Searching for new methods of making less energy-intensive materials by reducing their cost, adding local raw materials and industrial waste to the mineral resource base, as well as developing efficient production technologies is a relevant problem of the construction industry. A clinker-free technology for the manufacture of hydraulic binders will partially replace resource-intensive Portland cement in construction and help to solve these problematic issues to a certain extent and boost the environmental safety at the global level. The proposed binders, based on principles of structurization in alkaline systems as a combination of sequential and parallel physical and chemical transformations due to the contact interaction between fine powders of aluminosilicate nature and cations of alkali metals, contribute to the formation of strong and durable composites. Materials and methods. The study of energy dispersive microanalysis of components of the binder system was performed using the QUANTA 3D scanning electron microscope; dynamic light scattering was employed to study the particle granulometry with the help of the HORIBA analyzer. The strength characteristics of the binder systems “aspiration dust – bentonite – Na2O∙SiO2” were determined according to GOST 30744-2001 using Testometric FS150AT testing machine. Results. Electron microscopic analysis showed that particles of aspiration dust larger than 200 microns and smaller than 100 microns have a similar oxide composition, with a predominance of oxides of calcium, silicon, aluminum and carbon. The chemical composition of bentonite confirms the aluminosilicate nature. An increase in the physical and mechanical properties of specimens of the systems “aspiration dust – bentonite – Na2O∙SiO2” has been identified; it is the addition of higher dispersion bentonite that contributes to the dense packing of grains due to the volume-wise redistribution of particles, which positively affects the pore structure and water resistance of the cement stone. Conclusions. The results of the study have proven the new prospects for the alkaline activation of complex powders made of cement industry waste and bentonite clay; the characteristics and dependencies, obtained by the authors, will allow using the proposed technology in construction.