Increase in frost resistance of a ceramic brick from clay raw materials of the Atyukhtinsky field

The present article reveals the results of the fulfilled research on increase in frost resistance of a ceramic brick from clay raw materials of the Atyukhtinsky field by means of semi dry molding. Based on the analysis of published sourses, it has been established, that the most effective way to increase frost resistance of ceramic brick is an injection of different structuring additives into clay mass, which provide obtaining necessary characteristics of the porous structure of the material – a high content of reserve pores in the brick. In the function of an additive we have tested calcium-containing secondary products – wastes, extracted during the production of phosphate mineral fertilizers. The carried out researches demonstrate that the injunction of calcium-containing additive into clay mass with preliminary plastic preparation and following granulation leads to formation of optimal porous structure of ceramic brick and, consequently, to increase in frost resistance.

The modifying additive effect on the porous properties, when examining the sample, was defined by the fact that due to the additive injunction volumes of total and opened porosity in burnt ceramic samples increased. The additive did not affect significantly on capillary and closed porosity. The amount of reserve porosity of burnt ceramic samples increased 2 times with using of waste products. Because of this, frost resistance increased from 4 cycles (samples made from pure clay raw material) to 152 cycles (samples with additive). X-ray diffraction analysis showed that the rise in crystal phases content (anorthite and helenite) is an increase cause of strength of samples containing the additive.

It should be mentioned that the injunction of the additive in the already prepared molding powder, made according to the traditional technology (drying of the raw material and its grinding less than 3 mm) did not lead to a significant change in physico-mechanical indices of samples. In has been determined that the significant increase of frost resistance occurs only when injecting the additive during preliminary plastic preparation of clay mass with the following granulation – a little dried raw clay material ground less that 1 mm, mixed with the additive, after that grains 15mm in diameter were extracted from wetted mass and then ground less that 3mm.

In such a manner, the use of the modified calcium-containing additive in the molding batch composition and thereby achieved characteristics of the received products confirm the fundamental possibility of producing lining frost resisting ceramic brick of semi dry molding, as is evidenced by the results of carried out researches and pilot-scale tests. (paper)