Most European-grown wood species are susceptible to biological degradation, specifically, they suffer from a poor resistance against wood-destroying fungi. Therefore, prior to outdoor exposure, wood has to be treated either by applying a protective coating on its surface or by full-volume impregnation with antifungal chemicals. However, due to environmental and health concerns, the most frequently chosen solution, the use of biocidal preservatives, has become limited and new non-biocidal methods to protect wood against wood-destroying organisms are investigated. Recently, chemical wood modification via in-situ esterification of sorbitol and citric acid (SorCA) has been reported to result in a significant increase of the biological durability, specifically an increased resistance against wood-destroying basidiomycetes. However, none of these studies have investigated the resistance of SorCA treated wood against decay fungi by performing a full EN 113-2 (2021) procedure yet, i.e. following the standard incubation time and sample size. Therefore, a series of Scots pine sapwood (Pinus sylvestris L.) specimens was treated with aqueous solutions of SorCA at different solid content levels (10, 20, 30 and 50%). All treated collectives plus untreated reference samples were then exposed to brown rot (Coniophora puteana, Rhodonia placenta) and white rot (Trametes versicolor) fungi according to EN 113-2 (2021). After 16 weeks of incubation, wood decay was assessed on the basis of the loss in dry mass (ML %) and the decay protection threshold (ML ≤ 5 %) for SorCA-modified wood was established depending on the tested fungi. Post decay testing, the structural integrity of specimens characterized by various ML values was analysed by high-energy multiple impact (HEMI) tests and correlated with the ML resulting from decay by brown and white rot fungi. Basically, the structural integrity decreased with increasing ML in specimens being incubated with brown rot fungi, which was not observed after white rot incubation. The latter might be attributed to the narrow range of ML values measured after white rot incubation, indicating higher efficacy of SorCA modifications against white rot fungi. Thus, further work is needed to understand the difference in decay resistance between tested brown rot fungi and of course between brown and white rot fungi.

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