| Summary: | 碩士 === 國立宜蘭大學 === 自然資源學系碩士班 === 98 === Apitong, Douglas-fir, western hemlock, southern yellow pine, and radiata pine specimens of 9×9×180 cm (R×T×L) in dimension were treated by full-cell process with 2% ACQ, MCQ, CCA and 1% CA to produce preservative-treated wooden crossarms for mechanical properties and treatability assessments. Three tested wood species were selected to evaluate the decay resistance of wooden crossarms under outdoor exposure. The following conclusions were drawn from this study：
Southern yellow pine appears to be the most easily-treated wood species among the five species study by all the preservatives used in this study. MCQ shows outstanding penetration ability to Apitong, however, seems to penetrate softwood species poorly in comparison to the other preservatives used in this study. The most difficult species to be treated by preservatives is Douglas fir. In spite of wood species, CCA indicates best wood penetration ability, followed by ACQ and CA, while MCQ is the worst.
Except the CA treated southern yellow pine specimen, different preservative treated specimens within a single tested wood species indicate insignificant difference in specific MOE ratio. The CCA treated Apitong, Douglas-fir, western hemlock, and radiata pine specimens showed much lower specific MOE ratios than the ratios obtained from all the other wood species and preservative treatment combinations, which reveals that CCA has more negative influence on the bending properties of treated wood than the other preservatives.
The reductions in dynamic modulus of elasticity (DMOE) for most crossarm specimens tested were lower than 20% after 210 days of outdoor exposure, which implies that the preservatives used in this study do not significantly affect the DMOE of treated crossarms. The corrosion of washer contacted with CCA treated specimens was less than those contacted with specimens treated with other preservatives. Under 5% significant level, the ANOVA results reveal that the corrosion area of zinc coating steel washer contacted with ACQ and CA treated crossarms were larger than those in contact with CCA and MCQ treated crossarms.
The sapwood specimens of southern yellow pine treated with the four preservatives used in this study showed weight losses less than 3% after incubation with brown-rot fungus G. trabeum, however, when the fungus used turned to P. placenta, CA treated specimens did not reach the 3% weight loss criteria, which indicates that a higher preservative retention for CA is required to resist decay caused by P. placenta effectively.
The wood specimens treated with all the four preservatives used exhibits no obvious influence on the stainless steel nails imbedded into the specimens, while low-carbon nail and zinc coating steel nails imbedded into ACQ treated specimens display significant weight losses than those imbedded into CCA, MCQ, and CA treated specimens.
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