Comparative studies on the durability of English oak (Quercus robur L.) under in-service, field and laboratory conditions

IRG/WP 17-10881

C Brischke, L Meyer-Veltrup, A Soetbeer, M Höpken, E Melcher, J Trautner

The durability of many wood species varies due to differences in extractive content, anatomical features, growth conditions, and not at least in dependence of the respective exposure conditions either under test or in real life applications. And so does the durability of English oak (Quercus robur L.), which has recently been considered in the revised European standard EN 350 (2016) and is now classified as ‘durable to less durable’ (Durability class DC 2 – 4) in ground contact (Use class UC 4), but in case of standard lab tests using basidiomycetes as ‘very durable to durable’ (DC 1 2). To increase the knowledge about reasons of durability variation within one wood species, this study aimed on comparative evaluation of results from different laboratory, field and in-service tests with English oak. This paper considers the final results from three different projects with in-ground field tests after five, seven, and twelve years respectively. The three English oak assortments showed generally higher durability in decay resistance tests with monocultures of different basidiomycetes compared to tests using terrestrial microcosms (TMC). The results from the TMC tests, which can be seen as semi-field tests, were confirmed by the in-ground field test results at three different locations in Germany. Obviously, the degradation patterns under laboratory conditions in the TMC are similar enough to those in the field that they might serve as predictors for outdoor performance of wood. Finally, full-size double-split fence posts were exposed at the test field in Trenthorst in parallel with smaller EN 252 (2015) standard specimens. Standard specimens of all three Oak assortments decayed severely during five years of exposure in ground. In contrast, the heartwood portions of the full size fence posts was on average decayed less than 12 %, which might suggest a positive effect of bigger dimensions on wood durability in ground.


Keywords: durability, fence posts, in-ground testing, material resistance, service life prediction

Conference: 17-06-04/08 Ghent, Belgium


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