Influence of Iron-Containing Components on the Curing and Hardening Properties of Magnesium Oxychloride Binders

The article presents the results of studies of composite magnesium oxychloride iron-containing binders. The research is aimed at solving the problem of increasing operational durability and expanding the scope of application of magnesium materials. The purpose of the work is to study hydrate formation, hardening, and properties of composite magnesium binders with varying contents of iron compounds. Compositions of caustic magnesite (magnesium oxide) with iron oxides, with ferruginous minerals (andradite and pyrite), and with waste from the enrichment of magnetite ores have been studied. The scientific novelty of the research results lies in the identification of patterns of hydration of magnesium oxychloride binder with a high content (at least 50%) of iron compounds. The mutual influence of magnesium and ferruginous components during hydration and formation of the binder structure has been established. Schemes for the formation of hydrates involving andradite and pyrite have been proposed. The qualitative composition of the main hydrates of composite binders was determined by diffractometric and differential thermal analysis methods. The microstructure of the materials was studied by electron microscopy. The structure of magnesium paste made from a composite binder is formed by crystals of magnesium pentahydroxychloride and amorphous gel-like iron-containing hydrates. In composite binders containing iron oxide or andradite, magnesium hydroxychlorocarbonate is formed. The dependence of the stability of magnesium hydroxychlorocarbonate on the content of magnesium oxide and chloride was revealed. The patterns of the influence of iron compounds on the hydration and hardening of magnesium oxide form the basis for the development of a composite binder containing 50%–70% magnetite ore enrichment waste. A composite binder containing a ferrous man-made component is not inferior in strength properties to caustic magnesite and is characterized by high structural resistance to long-term operational impacts.