Comparison of technological properties of clay raw materials during the tests using plastic and soft methods of brick molding

The article presents the results of studies of technological properties of clay raw materials using the example of highly dispersed refractory clays of Vladimirovskoye deposit and low-dispersed fusible loams of Aksayskoye deposit in relation to plastic and soft methods of product molding. Research in this area is being conducted due to the lack of testing methods for clay raw materials in relation to the wet method of product molding, despite the fact that ceramic bricks produced using this production technology are in high demand in modern construction and architecture. In Russia, only a few companies produce bricks using this technology, and many companies have not yet been able to master this technology. Comparative tests on typical water-soaked clay raw materials showed that the existing accepted methods approved by regulatory documents cannot be applied to soft molding technology and that a separate method needs to be developed. Thus, with soft molding, molding materials are characterized by an increased degree of deformation under load, reduced plastic strength and critical compressive stress, as well as increased stickiness. It has been shown that a simple increase in the moisture content of molding materials leads to the deterioration in the basic pre-firing technological properties: air shrinkage, sensitivity to drying, cohesion; and to achieve the required degree of sintering, an increased firing temperature is required. Therefore, increasing the moisture content of molding materials is not a simple solution. Molding materials for soft molding must contain increased amounts of leaners with grain compositions approaching the densest packing and the presence of the required amount of sand fraction particles. Otherwise, obtaining high-quality facing ceramic bricks with high decorative properties becomes extremely problematic from a technological perspective. The results of the conducted research will allow to move closer to the development of a method for selecting raw materials for soft molding of ceramic bricks and, in practical terms, will help in organizing production using this technology.