An exploratory study on bamboo permeability for evaluation of treatability with chemical solutions

The rapid and uniform impregnation of resins and preservative fluids is critical to improving the quality and durability of wood-based materials. Permeability coefficients obtained in laboratory experiments aid in the development of optimal conditions for uniform resin filling on an industrial scale. However, due to the shape and orientation of pores in the bulk structure of bamboo, simplified permeability equations may not be sufficient to provide realistic resin impregnation predictions. In this study, the permeability coefficients for Dendrocalamus asper bamboo were determined using air flow measurements and Forchheimer's equation in the x, y, and z directions, and they were correlated to the bamboo microstructure, providing a detailed perspective on how to further investigate this property for real-world applications, such as pressure treatments with chemical solutions. Porosity was measured using mercury intrusion porosimetry (MIP) and water immersion methods to aid in the permeability analysis. The results showed that the longitudinal direction had 1000 to 10,000 times higher permeability coefficients than the radial and tangential directions. This finding is consistent with the alignment of transport vessels as well as the limited pore network in the transversal bamboo section. The outer region of bamboo had higher radial permeability than the middle and inner layers, despite having lower porosity. It is hypothesized that the greater number of vessels, albeit smaller, provides a more direct path for air to flow. The Darcian permeability coefficients of bamboo were found to be comparable to those reported in the literature for wood. This exploratory study provided insights into a novel approach for assessing the treatability of bamboo species.