Measurement of Shrinkage and Cracks Associated to Convective Drying of Soft Materials by X-ray Microtomography

Abstract

Traditionally, the measurement of shrinkage occurring during drying is performed by destructive or poorly accurate techniques such as volume displacement methods. Cracks detection and quantification are realised either by destructive techniques or sophisticated but expensive nondestructive ones (NMR imaging). X-ray microtomography in combination with image analysis provides an accurate, nondestructive and easy to use technique to determine simultaneously shrinkage and crack extent. Results reported in this article concern drying of wastewater sludges whose management will become a real challenge in the years to come. These results show a clear relation between drying kinetics and crack development. This could be related to the development of internal diffusional limitations inducing moisture gradients and mechanical stresses leading to cracks formation.

Keywords:

• X-ray microtomography
• Convective drying
• shrinkage
• Cracks
• Image analysis

Acknowledgments

A. Léonard is grateful to the FNRS (National Fund for Scientific Research, Belgium) for a Scientific Research Worker position.

The Ministère de la Région Wallonne, the Ministère de la Communauté Française de Belgique, and the FNRS (National Fund for Scientific Research, Belgium) are also gratefully acknowledged for financial support.