Fältförsök med träskyddsmedel för klass AB. Delrapport nr 2. Resultat efter 5 års exponering. Nordic Wood projekt nr 98056

• Since 1994 there are restrictions in Sweden on the use of chromium and arsenic containing wood preservatives. These preservatives are now in principle allowed for use in ground contact and water only. The use of chromium and arsenic free preservatives has increased and dominates the Swedish market for commodities above ground (Nordic wood preservation class AB). As the knowledge of the performance of these preservatives is limited, a field trial was set up in order to get more information about the durability in ground and above ground, discolouration by staining fungi, leaching, weathering and corrosion on fasteners in contact with the treated wood. Samples were treated according to class AB in commercial treating plants with the following preservatives: Basilit Bauholz KVD, Impralit KDS, Kemwood ACQ 1900, Tanalith E, Wolmanit CX-S and Wolmanit CX-8. Untreated spruce and heartwood of pine and larch were also included in the trial. In addition to testing according to EN 252 and ENV 12037 (lap-joint), both somewhat modified, testing was also carried out according to methods specially designed for this trial. After five years exposure the results show that: · No treated samples exposed above ground have yet been attacked and very few untreated samples only have been severely attacked by wood destroying fungi. There is thus some concern that the methods used, and in particular the lap-joint method, are not suitable for above ground testing in temperate climates. · The tests in ground indicate that with increasing copper content in the treated wood the better is the performance. · Heartwood of larch performs better than heartwood of pine in the in ground tests. On contrary, heartwood of pine shows better decay resistance than heartwood of larch in the above ground tests. · All samples are more or less attacked by bluestain fungi. Untreated samples are severely attacked. · Stainless steel has the best performance against corrosion. Wood treated with Kemwood ACQ 1900 and Wolmanit CX-8 seems to accelerate the corrosion of most other fastener materials. · The leaching of the chromium and arsenic free preservatives seems to be substantial whereas the leaching from CCA-treated references is little or moderate. For wood preservatives containing copper and an organic active ingredient, copper seems to be less susceptible to leaching then the organic component for which not only leaching but also chemical decomposition may take place.

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