Influence of clay shale and quartz sand on the ceramic masses molding properties in soft molding

In recent years, soft molding method of ceramic face bricks production has been increasingly implemented. This method allows making bricks with special decorative effects that unattainable for other molding methods, which makes the products very popular on the market. The peculiarity of this method is the molding masses increased water content in comparison with the plastic method and reduced water content in comparison with identical mass composition casting. Conventionally four soft molding bricks manufacturing technological methods can be distinguished. These are the actual manual products molding, the workpiece casting or overclocking molding method, the crushing method and the vibration forming method. For selecting raw material compositions a special approach to their molding properties assessment is required, including the additional indicators determination: the samples deformation degree, the critical compression stress, adhesiveness, as well as the elastic-plastic-viscous characteristics (plasticity, elasticity, the true relaxation period, etc.). The structural and mechanical properties are determined by the chemical and mineralogical composition and the molding masses structure. There are still few practical developments in the field of the soft molding. The article presents the study results of the clay shales and quartz sand (as leaners) effect of various grain compositions on the ceramic masses molding properties of soft molding. It has been found that for typical polymineral clays, at optimal humidity (≈ 20-25%), the clay shales or quartz sand addition of up to 50% reduce the masses critical compression stress by 20 times. It makes possible to apply soft molding various methods and create a variety of the brick front faces reliefs without increasing the water content of the molding masses.