Graduate Thesis Or Dissertation
 

Evaluating radial compression, color indicator and micro-toughness tests to detect early decay in Douglas-fir

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/kh04dv037

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  • Three methods--radial compression strength, color indicators of decay and micro-toughness, an examination of tracheid fracture patterns, were evaluated for detection of early decay and for application to field use. Three-eighth-inch diameter plugs 3/4-inch long, cut from the sapwood and heartwood of a Douglas-fir pole free of decay, were decayed by Poria placenta to weight losses up to 15% and tested at 13% moisture content. Strength losses at 5% compression strain and at the first load inflection point were similar and were highly correlated with weight loss. Strength losses occurred before weight loss was evident reaching 55% at a 10% weight loss. Sapwood decayed faster than heartwood but suffered similar strength losses at the same weight losses. Radial compression strength is controlled by the weakest earlywood band and is not affected by specific gravity, percent latewood or ring count. Chrome azurol-S plus sodium acetate was the most effective color indicator of decay by Poria placenta but not by other common decay fungi in Douglas-fir. Methyl orange plus indigo carmine, a good indicator of decay in Douglas-fir sapwood, often reacted with sound Douglas-fir heartwood. The needle micro-toughness test, which measures-the abruptness of tracheid fractures, works best on earlywood for detecting decay but is too tedious. Radial compression strength offers the most encouraging approach for detecting early decay and for estimating residual strength of wood.
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