STUDIES OF CHEMICAL INTERACTION OF MAGNESIUM OXIDE AND ELECTROLYTE SALT SOLUTIONS

Magnesia cement hydration runs very slowly, because its grains are covered with Mg(OH)2 coating, preventing the water access to MgO. It has been also known, that periclase and magnesia cements having burned grains can be gauged with solutions of various salts, thereby the setting time and the strength properties are changing [5; 6]. Purpose. Creation of fast-hardening and solid structure of magnesia stone by activating MgO with electrolyte salt solutions. The effects of MgO hydration in the electrolyte-salt solutions - MgCl2 and MgSО4 was shown. Conclusion. For the formation of magnesium stone with fast-hardening and solid structure was determined that it is necessary to apply to the method of activating MgO by electrolyte salts, and select a silica-containing component out of by-products with a surface area of grains more than 10,000 cm?/g for the formation of waterproof magnesium silicate hydrate. Samples hydrated in MgCl2 solutions of different concentrations exhibit two endothermic effects of the water of crystallization evolved at 160 and 240°C. The endothermic effect of magnesium hydroxide decomposition is shifted to 380°C. At 10 and 15 % MgCl2 concentrations, besides the above mentioned effects, at 415, 500, 520°C there are observed endothermic effects, associated with the decomposition of small amounts of magnesium oxyhydrochloride at such concentrations. It has been established that at low solution concentrations (? 5 %) magnesium hydroxide forms solid solutions with them. According to the data of the thermal gravimetric and chemical analyzes, the solid Mg(OH)2 solution, obtained by the hydration of MgO in 5 % MgCl2 and MgSO4 solutions, has the following limiting composition: [Mg(OH)1,88?Cl0,22]?0,20H2O and [Mg(OH)1,86? (SО4)0,07]?0,23H2O. When mixing cement by MgO solution of low concentration less 1,5 mol/l (13% or 1,1 g/sm) by end-product in stone structure is Mg(OH)2.