Effect of Supercritical CO2 Drying on Moisture Transfer and Wood Property of Eucalyptus urophydis

Wood dried using supercritical CO2 has unique properties because water is removed directly from the cell lumens through the cycling between supercritical and gas phases. Eucalyptus urophydis green wood was dried by supercritical CO2 at 50 °C and pressure of 10, 20, and 30 MPa; the effect of supercritical CO2 drying on moisture content distribution and transfer, as well as the permeability and extractive content of the wood, was investigated. The results showed that the supercritical CO2 drying rate was high, showing the highest drying rate at 20 MPa and the lowest at 10 MPa. Drying rate increased with pressure below 20 MPa in this study; drying rate represented no positive relation to pressure over 20 Mpa. Moisture content distribution was more uneven in the low-pressure drying conditions and in the middle transverse section of the specimens. The moisture content gradient in tangential was greater than that in longitudinal, especially for the drying of 10 MPa, indicating that water was removed mainly in the former direction of wood. More extractives were removed from wood at higher pressure during supercritical CO2 drying. Bordered pits were broken up more at higher pressure conditions. The decreased extract yields and increased amount of opened bordered pits increased the permeability of the wood after supercritical CO2 drying.

Masonry brick–cement mortar interface resistance to water transport determined with neutron radiography and numerical modeling

Masonry is one of the most common building envelope systems in the world, providing an excellent water protection solution against rain. Water transport in masonry walls composed of bricks and mortar joints can be strongly affected by the nature of the interface between brick and mortar. In this study, two-dimensional water uptake experiments and numerical simulations are performed to study the effect of interface resistance on moisture transport in masonry samples with horizontal and vertical interfaces. Neutron radiography is used to document the time- and space-resolved moisture content distribution in different masonry samples. In the simulation of moisture transport, an interface resistance models the imperfect contact between brick and mortar. A good agreement between measured and simulated moisture content distribution is observed for different masonry samples. Moisture transport in masonry could be strongly affected by the interface resistance, when interface is in proximity to moisture source. The orientation, horizontal or vertical, of the interface between brick and mortar does not have an influence on the value of the interface resistance. However, the interface resistance depends on the capillary pressure at the interface. In the range of capillary moisture transport, a lower capillary pressure at the interface will lead to a larger interface resistance.