BINDING MATERIALS ACTIVITY REGULATING BY MECHANICAL CHEMICAL METHODS

Abstract

It has been established that some abrading treatment of metals oxides crystallizing by halite crystal type (CaO, MgO) reduces their reactive capability. The activity reduction rate was substantially higher than that which could be explained by reducing of oxide specific surface. So, it is reduced for MgO by 30-40 %, while the oxide activity in the magnesium cement – by 250-1000 % (contrary to an impact treatment in a vibration mill). Similar results have been obtained for the interaction between calcium oxide and water, solutions of orthophosphoric acid and salts. CaO powder specific surface before and after abrading treatment by BET method reduces by 50-60 %, while variations of rate constant ranged from 1.5 to 34 times. The same mechanical treatment has a little effect on similar processes in systems where beryllium and zinc oxides are present (structure type of wurtzite). The reactive capability reduction for calcium, magnesium and cadmium oxides can be connected with some changes in the form of polycrystallites' particles in the abrading treatment process. The more prolonged abrading leads to plane sliding and some exposing flat surfaces those are characteristic for crystals of cubic syngony. Thus, an irregular defect layer is removed from grains. Small particles separated in the course of a mechanical treatment from rounded grains at the first stage (up to 5 min) show an increased activity, and then quite dense low active aggregates are formed. The more ordered zones, exposed in the course of an abrading, react slower in comparison to the initial grains, as well as to thin particles being split out. Due to this process the chemical activity reduces. On the contrary, zinc and beryllium oxides crystallites in the abrading treatment practically do not change their outline character; their chemical activity remains constant. Thus, the mechanical abrading treatment of oxides, which crystallize by halite type, really allows reducing their reactive capability in quite wide limits. This opens new opportunities in chemistry of binding materials, allowing achieving needed proportion between rates of chemical interaction and structure-forming in binding systems, which is a necessary condition for a solid monolith compositions' formation.Forcitation:Kosenko N.F., Filatova N.V. Binding materials activity regulating by mechanical chemical methods. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 1. P. 66-71