Wood in seawater - Investigations into the durability of modified wood in marine construction, especially against Teredo navalis

Despite its numerous strengths as a construction material, indigenous wood is increasingly being replaced in seawater by non-sustainably produced materials because it is not resistant to wood degradation in seawater. The most important marine pests are wood worms and clams. In Germany, Teredo navalis, a marine borer belonging to the mussel family, causes the most damage. The aim of this project was to increase the use of wood in seawater construction, specifically the use of wood from domestic production. This should be achieved by chemical modification of the wood. Various modification methods were compared and the general suitability of the treated timber for seawater construction, in particular its resistance to infestation by the marine borer Teredo navalis, was investigated.

Various modified woods were exposed to seawater and tested for durability in accordance with EN 275. During seawater exposure, the stability of the modifications against leaching was determined. Other typical stresses that occur when using wood in contact with seawater were investigated under laboratory conditions. Some of these stresses (e.g. infestation by drill lice) were already known. Further (e.g. weathering) had to be defined by comparison with other classes of use according to EN 335.

Some of the wood modifications investigated were already established processes (e.g. DMDHEU, melamine, acetylation). In addition, process engineering principles for treatment with phenolic resin and water glass (sodium silicate) were investigated.