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Because of inadequate storage space, some factories store their goods in open areas for long periods, as a result of which they are subject to atmospheric action, in particular, icing, which inevitably affects their structure and service properties.The Institute has carried out tests to determine the effects of cyclic freezing on the structure and properties of refractories (frost resistance).The method used for building materials was used [i, p. 251].Studies were made on blast-furnace bricks.Specimens cut from the bricks in the form of cubes with 30-mm edges and bricks in the whole state were first saturated with water, placed in freezing chambers, and held at minus 15-17~ for 4 h. They then were extracted and immersed in water for thawing.The total number of freezing cycles was 15. To explain the kinetics of frost resistance, we selected samples after i, 7, and 15 cycles.Before and after the experiment we determined the open porosity, the apparent density (GOST 24-09-67), the strength (GOST 40-71-69), and the thermal-shock resistance (GOST 78-75-56) of the specimens, and studies were made of their structure.The porosity and density data after i, 7, and 15 cycles came practically within the test accuracy limits although there was a certain tendency toward an increase in porosity with increase in the number of cycles.Compressive strength tests showed a significant spread in values, which is connected with the preparation of the specimens; this agrees with data in [2, 3], but on the whole there is a tendency to a reduction in the strength of the brick during the experiment, equal to 3-5% and in some cases up to 10%. • lO. Reflected light.

A number of reports [1][2][3][4] have indicated the need to enhance the quality of refractories for blast furnaces, particularly for the bosh and lower stack. One method of improving the properties of aluminosilicate refractories is impregnation with coal tar, coal-tar pitch, and other carbon-containing materials. This method is used in the manufacture of carbon-based artifacts of enhanced density [5][6][7]; Smirnov and Sobolev [8] recommend impregnation of refractories for lining oxygen steelmaking converters, and Simonov and Shubin [9] impregnation of the plates of sliding gates of steel-teeming ladles. It is noted that the higher is the coke residue, the greater will the extent to which the pores are filled with carbon, and the lower will be the wettability, particularly that of oxide refractories, by the metal; this increases their service life.On the basis of literature data [1,[5][6][7][8][9] and investigations, the Ukrainian Scientific-Research Institute of Refractories (UkrNIIO) has developed a procedure for impregnating chamotte refractories* to lengthen their service life in blast furnaces.The change in the macro-and microstructure of the refractories before and after impregnation with carbon-containing substance was investigated macroseopically and under a microscope, using transparent and polished sections and immersion preparations; furthermore, the structure was investigated with a U~MV-100A electron microscope, using a two-stage replica with a cleavage face. Contrast was bestowed on the replicas by oblique shadowing with metallic chromium.The initial refractories were found to have numerous pores (rounded, oval, or irregular) penetrating the refractory uniformly. The pores were generally confined to the binder and to the contact of the chamotte grains with it; we sometimes observed discontinuous (occasionally, continuous) cracks round the quartz and chamotte grains. The size of the pores ranged from 0.05 to 0.7 ram, but sometimes reached 1 ram.During impregnation of refractories, the carbon-containing substance penetrates mainly into the binder, which becomes dark gray (almost black), regardless of the number of impregnations; the chamotte grains in it are made conspicuous by their lighter color.The petrographic analysis data agree closely with the results of an investigation of replicas of chamotte grains of specimens subjected to impregnation and then to heat treatment. Under the microscope we see that the carbon-containing substance first penetrates into the cracks formed at the contact of the chamotte grains with the binder, and then enters the large open cracks and pores. Filling of the pores begins at the walls and progresses to the center. When filling is incomplete, the pore centers do not display carbon-containing substance. After impregnation and heat treatment, on replicas of the refractory we see that the pore surface is covered with a layer of carbon-containing substance, 0.15-0.35 pm thick (Fig. 1), which blocks and reduces the contact surface of the chamotte refractories.As shown by ...