Investigation of the hydration processes of magnesia stone from mechanoactivated caustic dolomite

Alternative Portland cement binders with low carbon dioxide emissions are currently being developed. One of them is caustic dolomite, which has low activity of magnesium oxide. The increased activity of magnesium oxide by mechaonoactivation in vortex layer devices will allow high-hydration magnesite stone and improved physico-mechanical characteristics. In this study we investigated the caustic dolomite powder and magnesium stone based on it. The X-ray phase analysis of the Rigaku SmartLab diffractometer was used to determine phase composition and structure. The hydration products were confirmed by results from differential thermal analysis in the STA 6000.The structures morphology, density, and compaction degree were assessed by the Merlin scanning electron microscope. It was found that, as a result of the mechaonochemical activation of caustic dolomite, а densely packed crystalline structure of magnesite stone is formed with a reduced porosity value, reduced crystallite sizes and unavailability of shrinkage cracks, which is a consequence of high contact density of crystallizing phases, accompanied by a general increase in strength of the magnesia stone. It has been proven that the activation of caustic dolomite contributes to the intensification of the hydration processes and to the formation of spatially-linked microstructure of magnesia stone due to stable phases of three-pentaoxyhydrochlorides, to a reduction in the porosity of the stone by 1,69 times and to reduction in the size of magnesium oxide crystals of 20% - up to 20,6 nm.