Improving the durability of low durability plantation hardwoods for use as power poles

Abstract

Australian energy distribution authorities may face a shortage of timber suitable for power distribution poles. This ongoing three-year research project is looking at potential replacement timbers from four plantation sourced species: Eucalyptus globulus (southern blue gum), E. grandis x camaldulensis, E. dunnii (Dunn’s white gum) and E. nitens (shining gum). Currently these plantation hardwoods are used for lower value products such as pulp (at around $30 per cubic metre); if their durability can be improved these hardwoods may sell as power poles for $165 per cubic metre.

The research is examining treatment characteristics, decay and termite durability and mechanical performance (i.e. MOR) of the four species. Samples from each species were treated with preservatives using industry standard vacuum followed by pressure techniques. Laboratory measurements indicate the absorption of preservative fluid is most affected by time at pressure rather than time at vacuum.

Together with untreated control samples, samples were placed in locations where decay would be expected to occur. After 21 months the samples were measured for signs of decay or insect attack, with no treated timber showing signs of attack. This exposure testing is continuing.