Durability of wood

At present a rapid-train track is built between downtown Stockholm and the international airport of Arlanda. It is partly passing through densely populated suburbs and therefore noise barriers are built along the track. They are about 3 meters in height and built in sections of 4 meters each and the main part is made of larch /Larix sp/. These wood species have a high content of heartwood and is therefore expected to have a higher durability than many other commonly used wood species e.g. pine or spruce. However, the applicability of this is disputed and experimental studies are needed for verification. In order to compare the deterioration of latch with other species nine of the sections have been replaced with other wood materials with and without additional treatment. Four of these use new, arsenic-free, impregnation systems and two use a well established CCA-based system. In the test series untreated pine and spruce as well as the original latch is also included. All materials have been carefully documented, regarding relevant material properties for the wood and the treatment systems. In the paper an overview of the test set-up is given. The test has been running for approximately three years and no distinct results can or should be seen so far. The deterioration process will be evaluated on the basis of visual inspections as well as microscopical studies. An evaluation based on the environmental conditions is also planned. The results are expected to give a good base for judging and comparing different treatment systems, and type of wood. Furthermore, to make it possible to model the deterioration process in the view of the modern SLP concept (Service Life Prediction).