Decay resistance of out-of-service utility poles as related to the distribution of residual creosote content
Decay resistance of out-of-service poles was investigated to evaluate their effectiveness against biodegradation for possible recycling of these poles for composite products. Decay resistance was related to creosote content and creosote distribution in poles with service durations of 5 and 25 years and also freshly treated poles. Weathering of the poles had caused reduction in creosote content such that the residual content of the outer and upper portions of the poles was lower than the inner and bottom portions. Overall residual creosote content in the 5-year poles was lower than in freshly treated poles, but still higher than in 25-year poles. Above a 14 percent level of residual creosote content, the decay resistance of weathered poles was still high. Below that level, the decay resistance decreased dramatically. Decay resistance of 5-year poles was mostly still comparable to freshly treated poles, while the decay resistance of 25-year poles, especially in the outer portions, was much lower and approaching that of untreated southern yellow pine. In reutilization of out-of-service poles for composite woodproducts, components with lesser creosote content should be placed in the interior, while those with higher creosote content are more suitable for the outer part.