Studying the specific features of the hydration processes of alumina cements based on the compounds of CaO–NiO–Al₂O₃ system

The article gives the results of studying hydration processes occurring in cement synthesis using waste products of chemical industry. Cement clinker was synthesized with the relation of initial raw components, calcium-containing water treatment waste and rejected nickel containing catalyst of AZOT Private Joint Stock Company (Severodonetsk, Luhansk Region, Ukraine), equal to 50/50. The obtained samples were studied by Strelkov minor method: normal density, setting time and mechanical strength were determined within 1, 3, 7 and 28 days. The results regarding the setting product were analyzed by differential thermal, X-ray phase analysis, microscopic analysis and electron microscopy; this enables to control the phase relation in the synthesis of a new class of aluminate cements using waste products of chemical industry. The obtained data showed the absence of cubic hydroaluminates which deteriorate the strength. The methods of physicochemical analysis revealed that the phase composition of hydrated alumina cement is represented by calcium hydroaluminate of different basicity, whereas cleavage structure consists of prismatic crystals which give dual coalescence, and this is favorable form to provide matrix self-reinforcement. The developed composition of aluminous nickel-containing cement referred to hydraulic binders. The results of physical-mechanical tests of the synthesized cements indicated that the obtained cements are quick-setting, fast-hardening and high-strength materials