Date of Award

1997

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Renewable Natural Resources

First Advisor

Elvin T. Choong

Abstract

This study on the recycling potential of out-of-service poles for use in engineered wood products involved determination of basic properties of used southern pine (Pinus sp.) utility poles and also manufacture of glued-laminated beams from these poles. Most of the defect-free portions of 25-year treated poles still retained adequate strengths comparable to those of freshly treated poles and untreated southern pine. Creosote contents, however, diminished with pole ages. The reduction in creosote content was correlated with lower decay resistance, poorer dimensional stability, and lower lumber recovery, but better gluability. The spectrometry method for creosote content determination was explored as an alternative to the time-consuming standard toluene extraction method, and the results were comparable. Steam treatment could remove creosote to about 1.5 percent of its content regardless of initial creosote contents of the poles. Two- and 3-ply laminated beams were fabricated by gluing laminae from both treated poles and from untreated southern pine. The strengths of 2-ply beams assembled with an edge-to-edge gluing method decreased with increasing number of laminae for treated poles as well as untreated southern pine. Strengths of 2-ply beams from treated poles were lower than those of 2-ply beams from untreated southern pine, but still comparable to strengths of defect-free southern pine lumber. In 3-ply beams, fabrication was done with end-to-end gluing method. Increasing the number of joints caused a steady reduction in strengths, with finger-jointed beams exhibiting lower strengths than scarf-jointed beams. The overall strengths of jointed beams were lower than those of unjointed beams. All beams from treated poles, either jointed or unjointed, had strengths lower than those from untreated southern pine beams of the same construction. However, 3-ply beams from treated poles with scarf-joints had strengths comparable to those of defect-free southern pine lumber. Results of this study indicate that high performance engineered wood products in the form of laminated beams can be fabricated from out-of-service utility poles. Factors affecting strengths, such as residual creosote content, number of glued laminae, type of gluing, and number and type of joints are taken into consideration. Laminae with high strength and high creosote content should be placed on the surface, and low strength and low creosote in the inside, with little or no additional preservative treatment.

ISBN

9780591591507

Pages

202

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