Long-term performance of DMDHEU-treated wood exposed in ground, above ground and in the marine environment

IRG/WP 18-40825

L Emmerich, H Militz, C Brischke

Chemical wood modification with N-methylol compounds such as 1.3-dimethylol-4.5-dihydroxyethyleneurea (DMDHEU) has been studied intensively since the 1990s. Research of the past years focused on treatment of Scots pine (Pinus sylvestris L.) and European beech wood (Fagus sylvatica L.) and was shown to be applicable to improve specific material properties. A high resistance against wood-destroying fungi was proved in various laboratory trials with basidiomycete monocultures and in soil substrate, by means of mass losses (ML) corresponding to durability class (DC) 1-2 (‘durable to very durable’). This paper reports on the field performance of DMDHEU modified wood exposed above-ground (UC3, rail test, block test, deckings), in-ground (UC4) and in the marine environment (UC5). The aim of this study was to evaluate results from more than 7 years field testing with respect to the DMDHEU treatment level, wood species (Scots pine, European beech, Spotted Gum (Corymbia maculata K.D. Hill & L.A.S. Johnson), Slash pine (Pinus eliottii Engelm.)) and climate conditions at the different test sites. Field studies with different test procedures were started in 2003 (Moitas, Portugal), 2007 (Redlands and South Johnstone, Australia) and 2008 (Stamsmåla, Sweden; Goettingen, Germany). The same material was exposed in Australia and Sweden. Untreated, UC3 and UC4 (CCA) treated as well as modified wood indicated different severity at different locations. In general, DMDHEU was shown to significantly improve the biological durability of non-durable Scots pine sapwood. After exposure above-ground and in-ground under different climate conditions, DMDHEU treated Scots pine was classified as ‘durable to very durable’ (DC 1 - 2). Tests under UC5 conditions were started in 2008 in the North Sea (Wilhelmshaven, Germany) and the Baltic Sea (Hejlsminde, Denmark). After 9 years of exposure, Scots pine sapwood treated with DMDHEU was classified as ‘very durable’ (D) also under UC5 conditions with respect to attack by the shipworm Teredo navalis. However, DMDHEU modification seemed to be more efficient in pine wood so that higher chemical loadings are required for beech to reach similar resistance against wood-destroying fungi.


Keywords: chemical wood modification, DMDHEU, durability, field tests, N-methylol, use classes

Conference: 18-04-29/05-03 Johannesburg, South Africa


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