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.