Service trial of different materials exposed in jetties at Öresund. Progress report No. 5
This report contains results of the fifth inspection on the performance of different decking materials – preservative-treated wood, modified wood, natural durable wood, re-cycled plastics and wood-plastic composites (WPCs) - available on the market and exposed since 2013 (some since 2014 and 2016) by the City of Malmö in two jetties near the Øresund Bridge, south of central Malmö in Sweden. The objective of the test is to gather information on performance with respect to appearance, durability and function of the tested materials.
The test has, in spite of the relatively short exposure time, provided useful information on the properties of the different materials and their suitability for outdoor end-uses exposed to severe conditions.
The colours of all wood materials quickly became greyish, whereas the colour of the WPCs and re-cycled plastics remains roughly the same as the original, although somewhat faded, after approximately 101 months’ exposure.
All materials apart from the re-cycled plastics have been more or less attacked by disfiguring fungi or algae, and in some cases by lichen as well.
Decay was found in one plank of Organowood silica-modified wood after approximately 65 months’ exposure, and after another 12 months all Organowood planks were attacked by decay, which has further developed since. The decay is very likely caused by poor efficacy of the silica-based product. Incipient decay has also been found in Europen oak, black locust/robinia, roble, Kebony (one little spot only) and in one plank of Scots pine heartwood, superficially treated with Sioo, another silica-based product.
The mechanical properties vary considerably between the materials. Planks of European oak, black locust/robinia and roble have all been subject to checks, edge fractures and splinters. The use of these materials for jetties, boardwalks and decking where injuries to bare feet is a risk, should be avoided. Grooved material of bangkirai, azobé and Thermowood seems susceptible to more mechanical influence than non-grooved material.