The impact of heat treatment on the microstructure of a clay ceramic and its thermal and mechanical properties
Résumé
This paper presents the results of an experimental study on the microstructure, the thermal and the mechanical properties of a clay-based ceramic used in building applications. The X-ray tomography analysis showed a layered microstructure of clay with 200 mu m sheets of porosity after the extrusion process. The gas release from the dehydration, dehydroxylation and decarbonation induced a 7 vol% formation of porosity during the heat treatment of the clay-based ceramic up to 850 degrees C. The porosity increase and the development of metakaolin led to a 38% decrease in the thermal conductivity. On the other hand, the Young's modulus of the clay-based ceramic was conserved due to the formation of smaller pores than the 200 mu m sheets of porosity. The densification and the crystallization of amorphous phases also led to a 110% increase of the Young's modulus from 850 degrees C to 1050 degrees C. The Young's modulus of the clay-based ceramic was only decreased by the 13 Kt quartz inversion of the cooling due to sand addition. Hence, this study provided a useful insight into how the microstructure of fired clay bricks can be specifically transformed by the porosity during the heat treatment to control the thermal and mechanical properties.
Domaines
Sciences de l'ingénieur [physics]
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