NMR imaging of free and bound water transport during wood imbibition and deformation
Abstract
During water imbibition in wood, moisture penetrates not only in liquid form (free water) into the pores of wood, but a fraction of water molecules is also absorbed within the cell walls (bound water) reducing the swelling of the wood material. Although wood-water interaction has been studied for decades, the dynamics of water transport during imbibition and its interplay with bound water and deformation are still poorly known, in particular due to a lack of direct internal observations. Moreover, some curious facts have been observed and studied, for example, the permeability depending on the sample length is in contradiction with Darcy’s law which a priori describes liquid transport through a homogenous porous medium. Our original experimental approach, allowing to follow at the same time deformations and bound and free water, makes it possible to clarify some aspects of this problem.