Borziak O. Regulation of contact interactions to increase the resistance under operating conditions of materials based on mineral binders

The dissertation is devoted to the development of theoretical foundations for obtaining composite materials with improved operational properties based on mineral binders. Due to the directed regulation of contact interactions in composites, it is possible to increase the durability of structures. In the process of forming the structure of an artificial stone during the hydration of mineral binders, a significant role is played by the electric charges of the surface of binders’ particles, products of their hydration, filler grains. The influence of the crystal structure and formation conditions on the surface properties of minerals has been investigated. It has been established that crystal hydrates of anisometric morphology can be characterized by a significant difference in the electrosurface potential of different faces, up to opposite values. The electrosurface potentials of minerals, which are the products of hydration of mineral binders with an anisometric shape, have been calculated. It has been established that the electrosurface properties of carbonate materials depend on their genesis. Organogenic carbonates, in particular chalk, have a negative surface charge due to the presence of silicic acid on the surface, in contrast to chemogenic calcite, the surface of which is characterized by a positive potential. The main provisions of colloidal chemistry and physicochemical mechanics of mineral binders and composite materials based on them have been developed. Classification of structures and contacts in materials based on mineral binders have been improved. Using the example of a cement stone, the interaction energy was calculated for each type of contact. The energies per chain between potential-determining ions are calculated. The interaction energy increases from coagulation contacts to condensation contacts as the contribution to the total interaction energy of ion-dipole and ion-ion interactions increases. The specific interaction energy per unit contact area is determined by the surface density of individual contacts between potential-determining ions and the fraction of the contact area in the total cross section of the material. It has been established that the strength of an artificial stone depends on the ratio of oppositely charged surfaces in it. The regulation of the physicomechanical and hydrophysical properties of an artificial stone based on mineral binders is possible provided that the required balance of active areas of the surface of dispersed particles with negative and positive surface charges is ensured. An increase in the hydrophysical and physical and mechanical characteristics, crack resistance, and corrosion resistance of composites based on mineral binders is possible due to the introduction of complex chemical additives that promote the synthesis of additional crystalline hydrates with specified surface properties and mineral microfillers. Thermodynamic calculations were carried out in order to study the synthesis of additional crystal hydrates, as well as the probability of the interaction of mineral binders with mineral additives. An increase in the physicomechanical and hydrophysical characteristics of the compositions due to the introduction of mineral and organic fibers and mineral microfillers, taking into account their surface charge, has been substantiated. It was found that the surfaces of fibers and particles of microfillers are substrates for the growth of crystal hydrates, and electroheterogeneous contacts are formed between them. Structural and mathematical models of composite materials based on mineral binders with polydisperse mineral fillers, taking into account their surface charges, have been developed. The adequacy of the developed schemes is confirmed by the results of physicochemical studies. It was found that the introduction of such fillers ensures the formation of a dense structure of a composite material with a large number of electroheterogeneous contacts, in which crystal hydrates are maximally protected from contact with water and dissolution. The influence of aggressive media on contacts between dispersed particles in artificial stone is investigated. It has been established that an additional factor of aggressive action of acidic liquid media is an increase with a decrease in pH in the magnitude of the electrosurface potential of compounds with a negative surface charge to positive values.