From dry pressing to plastic forming of ceramics: Assessing the workability window


The shaping water content in clay-based ceramic building materials has conflicting implications in shaping and drying, decisively contributing to the cost-effectiveness of the industrial process. This work addresses the long-standing difficulties related to the quantification of the workability window for plastic forming. From uniaxial compression stress-strain curves, the yield stresses of mixtures of a red-firing clay and a ground basalt rock with different moisture contents were obtained. Combination of those results with the wet and dried bodies densities, showed that ceramic powders can be shaped only while in the funicular state: for this clay, dry pressing is effective above the pendular-to-funicular transition (similar to 5.7 wt% moisture) and the workability window for plastic forming begins at the maximum dried body density, which signals the transition from open-to-closed gas pores in the funicular state (similar to 15 wt% moisture), and extends to the funicular-to-capillary transition (similar to 18 wt% moisture). Drying did not alter the moist particle structure, which enables the expeditious determination of the workability window from dried body density and initial moisture content. (C) 2018 Elsevier Ltd. All rights reserved.



subject category

Construction & Building Technology; Engineering; Materials Science


Schiavo, LSA; Mantas, PQ; Segadaes, AM; Cruz, RCD

our authors


Authors gratefully acknowledge the financial support from the Brazilian agencies Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES, MSc scholarship) and Secretaria de Desenvolvimento Economic, Ciencia e Tecnologia (SDECT) of the State of Rio Grande do Sul, Brazil, and very much appreciate the contribution of the Institute for Ceramic Materials (IMC) technical staff towards the execution of the experiments throughout this work.

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