This research project is inspired of a COST Action FP 1303 “Performance of bio-based building materials”. The aim of present performance test was to examine the performance data of Norway Spruce specimens with different impregnations in outdoor environment and analyze Norway Spruce resistance to aging and how different impregnation cycles change the wood resistance to aging. A folding table was set up with 9 specimens made from Norway Spruce with three different vacuum-pressure-vacuum impregnation cycles using chromium free wood preservative – Impralit®-KDS. Specimen groups 1 and 3 were impregnated according to hazard class HC-4 and specimen group 2 according to HC-3, which end uses are respectively for outside ground contact and for outside non ground contact. Specimens made from board number 1 were made with rather long impregnation cycle and the amount of impregnant was about 10 times more than required by the impregnant manufacturer. Specimens made from board number 3 were similar to usual products and amount of impregnant was same as usually used. The boards were fixed with partly stainless and partly galvanized steel screws. 8 electrodes, for measuring moisture content, were mounted into the specimens, specimen 3/3 is without an electrode and it was evaluated only visually. Temperature sensors were mounted into specimens 1/2 and 3/2. All the data was recorded hourly during the duration of the performance test. Decay, discoloration, development of mould and other staining fungi, corrosion, formation of cracks and moisture performance were evaluated regularly. The first results after 3 weeks of exposure showed that the discoloration of the specimens group 2 is slightly smaller than others but the overall discoloration of specimens after 3 weeks is rather similar. Evaluation of surface disfigurement due to mould and staining fungi was done visually and no surface disfigurement was detected. The surface of stainless steel screws was intact, but the surface of galvanized screws was visibly, which means 5-50% of surface was attacked. These results are in correlation with the wood moisture content, which was all the time higher than the considered level needed for fasteners corrosion which is 15-20 percent. Specimen group 2 stands out as specimens with most cracks, which could be the result of much lower wood moisture content they have compared to other specimens. Again specimen group 2 stands out as the specimens with lowest wood moisture content and specimen group 3 has specimens with the highest wood moisture content, which was average of 28 percent higher than moisture content of specimen group 2. When wood moisture content did not respond so rapidly to changes of air moisture content then wood temperatures are in direct relation to air temperature.
Keywords: impregnation, Norway spruce, aging, performance test
Authors
Tubli P.
Department of Polymer Materials, Tallinn University of Technology, Tallinn, Estonia
Kallakas H.
Department of Polymer Materials, Tallinn University of Technology, Tallinn, Estonia
Kers J.
Department of Polymer Materials, Tallinn University of Technology, Tallinn, Estonia
Brischke C.
Faculty of Architecture Landscape Sciences, Institute of Vocational Sciences in the Building Trade, Hannover, Germany
Humar M.
University of Ljubljana, Biotechnical Faculty, Department of Wood Science and Technology, Ljubljana, Slovenia
Jones D.
SP Technical Research Institute Sweden Drotting, Stockholm, Sweden
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