Results are provided for comparative evaluation of the properties of pressed specimens of a matrix system and ceramic concrete specimens prepared on the basis of bauxite with very fine quartz glass and quartz sand (VFQG and VFQS), and also the thermal expansion of castings based on a suspension of quartz sand, bauxite and bauxite ceramic concrete. It is established that high-silica molded and unmolded ceramic concretes prepared on a basis of bauxite VFQG (85%) and VFQS (15%) have improved physicomechanical properties. After firing at 1150 and 1420°C their open porosity is 16 -18% and the ultimate strength in compression is 95 -125 MPa. Their temperature for the onset of softening is above 1570°C and higher than 1650°C (for compositions containing SiC).Keywords: very fine silica, matrix system, ceramic concrete, bauxite suspension, open porosity, apparent density, ultimate strength in compression, change in linear dimensions, weight content of matrix system, temperature for the onset of softening, mullite formation.As formulated previously [14], ceramic concretes are considered as composite (heterogeneous) materials consisting of a matrix or binder system (HCBS (highly concentrated binding suspension) of an appropriate composition) and a refractory filler. It is conditionally assumed that the matrix exhibits the properties of continuity, but the filler has an interface. Here grains of filler only in a limited way (with a surface) react with the binder system. The matrix is conditionally assumed to be homogeneous. It combines into a single whole numerous polydispersed single particles, that give solidity and prescribed shape of an object or lining. The matrix provides transfer of mechanical and thermal stresses to the filler, and it may also partly prevent it from corrosive action due to its fine capillary structure impermeable to melts [5,14].A considerable proportion of ceramic concretes in the systems Al 2 O 3 -SiO 2 , Al 2 O 3 -SiO 2 -SiC, Al 2 O 3 -SiO 2 -SiC-C are currently produced using a matrix system based on bauxite HCBS, containing VFQS (10 -12%), in the form of unmolded refractories, for example ramming mixes for monolithic linings [5]. The structure of these refractories is formed directly during service. In addition, the area is expanding for the use of molded refractories based on bauxite HCBS that are subjected to prior firing at 1100 -1430°C [8, 9]. The authors of this article have studied a version of the technology for molded refractories prepared by compaction. According to this technology the original HCBS, having a moisture content of about 12%, are mixed with a polyfraction filler (densely sintered bauxite with a porosity up to 5% or electrocorundum) and a plastifying addition is made to the mixture obtained. Compaction is accomplished in friction or hydraulic presses at a pressure P 15 -200 MPa. Depending on the type of filler used the refractories prepared by this technology in accordance with the generally accepted classification [6] relate to mullite corundum (for example grade MKTP-85) ...
