The behavior of different clays subjected to a fast-drying cycle for traditional ceramic manufacturing

Abstract

Studies have been widely carried out on drying techniques and equipment. The behavior of clays subjected to drying stages requires further research. This study aims to evaluate the behavior of the clay ceramic body during the different stages of the drying cycle and match the characteristics of the raw materials with the final quality of the pieces. In this work, the behavior of three different clays in terms of drying performance was studied. The clays were selected, and their chemical, mineralogical, and particle size characteristics were measured. The mixture design (DoE) developed 10 formulations and was processed through vacuum extrusion. The samples were subjected to forced drying cycles of 180 min by varying the temperature from 30 to 90 °C and air speed from 1.5 to 4.0 m/s. At the end of the cycle, the retraction was a determining factor for the crack probability indicator, where formulations that obtained ∼10% retraction in the dry zone showed losses >25%. On the other hand, it is could be stated that claystone assists the drying process of the ceramic piece, minimizing losses. The drying sensitivity coefficient (k-factor) presented values that reproduce the number of losses during drying, proving to be a valid tool to relate clay properties, drying conditions, and losses in this process. In this case, drying process losses >25% were observed when the k-factor was from 1.6.