Assessment and Characteristics of Molding Masses Based on Loam during Production Soft Molded Ceramic Brick

Abstract

опThe article discusses the issues of assessing the properties of loams and selecting the composition of molding compounds based on them for the production of ceramic bricks using the soft molding method. It is noted that for soft molding technology, to date, no recommendations have been developed for the evaluation of raw materials with the establishment of relationships between the composition, technological properties, molding features and aesthetic features of the front edges of products. According to technological features, the method of soft molding of ceramic bricks is conventionally divided into 4 methods: manual molding, accelerated molding, pressing method and vibration molding method. The results of our work made it possible to identify the main indicators when assessing clay raw materials and to develop the basic principles for selecting the composition of molding masses. Thus, the critical compression stress and the degree of deformation of the workpieces should be on average 0.2–0.8 kg/cm2 and 3–5 units, respectively. In this case, the molding masses should have the minimum possible water content and stickiness, have minimal air shrinkage (less than 6–7%), and be slightly or moderately sensitive to drying. An algorithm has been developed for selecting molding compounds, including determination, in addition to generally accepted indicators, such as the degree of deformation and critical compressive stress at different water contents, specific penetration resistance, determination of the optimal electrolyte content, and stickiness. For typical loams, the dependences of the degree of deformation of the samples and the critical compressive stress on the water content of the molding masses are shown, as well as the influence of electrolytes on the water content. It has been shown that the introduction of electrolytes can significantly reduce the water content of molding masses. It is noted that the genesis of loams, their variable composition and the frequent presence of undesirable harmful impurities predetermined the situation that high-quality loams that meet the necessary requirements are quite rare and the only alternative can be the selection of compositions of molding compounds based on correct scientific and methodological