Silica, the commonest material in nature, is used as the basic material in silicate technology. The extensive use of quartz sands and quartzites, particularly in a finely dispersed state, has made it necessary to study the processes of dry and wet milling various types of silica [1-3].By contrast with the coarsely dispersed or low-concentration quartz suspensions [4, p. 254; 5, p. 220], the high-concentration, comparatively finely dispersed suspensions of quartz sand seem promising for refractory technology since, after dewatering, these suspensions form a strong material. The study of such suspensions which have properties similar to those of vitreous silica [3, pp. 34-142] is of interest in the task of using these materials as a binding agent for ceramic concretes [6], as mixtures for molding light weight Dinas articles, as refractory solutions, coatings, and plastic refractories.

A promising refractory material is quartz--ceramic concrete [1]. The filler in this material is quartz--ceramic cullet and the bonding is formed by removing the water (pumping out of moisture and drying) from concentrated suspensions of vitreous silica. The study of the main properties of the quartz--ceramic concrete and the dependence of these on the firing temperature (heat-treatment temperature) seems to be of interest. The present article deals with these questions.

of CaO is reduced to 20%. However~ the tendency for the wear resistance of the refractories to increase with a reduction in their concentration of CaO is destroyed when the articles of a magnesite composition are tested since these are more resistant than those with 20% CaO. This is explained by the fact that the articles of the magnesite composition are penetrated more deeply by the melt and the degree of slag concentration is higher in the reaction zone. Consequently, the refractoriness of the zone is reduced and it is more intensively washed away by metal and slag. CONCLUSIONSWe have studied the properties of the refractories prepared from periclase--lime clinkers with a CaO concentration of 2 to 60%. It is established that as the concentration of CaO is increased, the rate also increased at 1500-1650~ the degree of dissolution of the refractories in slag is reduced; and in connection with this, their wear resistance is also lowered when tested under conditions simulating, in a first approximation, normal production conditions.The wear-resistance of the fired, pitch-impregnated refractories is higher than for the resin-bonded refractories of the same composition; this is the result of their greater density and strength at the test temperatures.The stability of the resin-bonded refractories made from synthetic clinker with 20% CaO is roughly 20% higher and that of the pitchimpregnated fired refractory 40-50% higher than the resistance of the resin-magnesite refractories normally used in production.

In ceramic concrete technology [1, 2], the process of structure formation and the properties of the material are significantly affected by the characteristics of the filler (size, specific surface, polydisperseness, porosity, etc.).The present article gives some results of a study of some of the technological factors which determine the kinetics of structure-formation, macrostructure, and strength of a ceramic concrete using, as an example, suspensions of vitreous silica {filler). The size of the single-fraction filler was varied from 1-40 mm with a constant porosity (11.0%). The characteristics of the suspensions with the exception of density (viscosity) were in all cases constant and corresponded to those suspensions used for the production of quartz ceramics [3]. The specimens of ceramic concrete were molded in gypsum molds (cubes with a side of 70 ram) and, depending on the grain size of the filler, the density Ps of the suspension was controlled between 1.70-1.89 g/cm 3 in order to provide comparable permeability (duration of impregnation of filler framework by the suspension) by changing the viscosity.The specimens of ceramic concrete with a rigidly fixed framework [1, 2] were molded by a method which included individual packing [4], involving filling the molds with filler and then pouring the binder suspension into the framework. The structure formation is achieved by a dewatering mechanism as a result of the active porosity of the filler and the partial porosity of the mold. fraction of single-fraction filler Cfv packed first into the mold by shaking was 0.50-0.52 re-The volume gardless of the particle size D~ s (from 1-2.5 up to 30-40 ram) determined by sieve analysis.

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