This paper presents preliminary results from a 13-month field test containing pine sapwood samples (Pinus sylvestris) impregnated with a mixture of siloxane and organic biocides using supercritical carbon dioxide as carrier. Samples were exposed above ground at a Danish field test site using matched non-treated sapwood controls for every treated sample. All samples were painted before exposure. Pine heartwood (Pinus sylvestris) was used as reference material. Acceleration of water uptake was achieved by cutting a groove in the samples across the grain after paint application. Water uptake was monitored by periodic weighing of the samples to establish the weight gain resulting from water sorption from the environment. After 13 months of exposure the siloxane treated samples with a weight percent gain (WPG) of 1.0% had an average moisture content of 33% while the non-treated controls had a moisture content of 78%. The heartwood samples had a moisture content of 29%. Paint adhesion was higher on the siloxane treated samples than both the non-treated sapwood and the heartwood samples as judged by visual inspection. The field test design seems to be an efficient way of accelerating water uptake and wood degradation and the supercritical siloxane treatment has proved to significantly decrease the uptake of liquid water in exposed samples.

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