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Wood Deterioration and its Prevention

Wood Deterioration and its Prevention. Wood Losses. 10 % of all wood cut in the U.S. replaces wood that has failed in service. Biotic vs Abiotic. Abiotic: Non-living agents Heat: (>150 F)(Fire) hemicellulose>cellulose>lignin Chemicals: Strong bases, strong acids, salts

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Wood Deterioration and its Prevention

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  1. Wood Deterioration and its Prevention

  2. Wood Losses 10 % of all wood cut in the U.S. replaces wood that has failed in service

  3. Biotic vs Abiotic • Abiotic: Non-living agents • Heat: (>150 F)(Fire) hemicellulose>cellulose>lignin • Chemicals: Strong bases, strong acids, salts • Mechanical: impacts, erosion • Sunlight: UV weathering attacks lignin

  4. Biotic Agents • Fungi • Insects • Woodpeckers • Marine borers

  5. Water Oxygen (air) Temperature Food

  6. Biotic Requirements • Water (>20% MC but really 30 % or the fsp) • Moderate Temperature (32° to 100°F) • Oxygen • Food

  7. Where is the Water in Wood? • Occurs in two locations: • Within cell lumen • Liquid • Called free water • Within the cell wall • Captured in cell wall matrix • Called bound water Liquid Free Water Cell Wall with Bound Water Wood & Water

  8. Free Water • Free water is liquid water that fills wood’s void spaces and affects only • Thermal conductivity • Mass Free Water Wood & Water

  9. From Haygreen & Bowyer (1989) Equilibrium Moisture Content The Equilibrium Moisture Content (EMC) is the MC of wood when it is in equilibrium with the environment’s temperature and humidity. Wood & Water

  10. Temperature & Humidity EMC of wood at various temperature and humidity values Wood & Water

  11. Bacteria • Remove pit membranes • Degrade extractives • Digest cell walls (Tunneling) • Can be important in submerged wood

  12. Fungi

  13. Fungal Spores are Everywhere

  14. Fungal Types • Molds/Stain Fungi • Soft rot fungi • Brown rot fungi • White rot fungi

  15. Green Fungal Hyphae in Wood

  16. Blue Stain http://www.forestry.ubc.ca/brchline/98sept/page4.html

  17. Mold on sapwood

  18. Mold Species • 250 to 300,000 species • 45 species on Douglas-fir sapwood lumber in the first 6 weeks

  19. Decay Fungus Fruiting Body

  20. Brown Rot

  21. White Rot

  22. Damage by True Dry rot Fungus

  23. Example of Decay Fungus in Culture

  24. Soft Rot on a Utility Pole

  25. Southern pine

  26. Southern pine with soft rot

  27. Soft Rot on a Eucalyptus pole

  28. Decay Effects • Reduced bending strength • Reduced acoustic/insulation value • Increased permeability • Increased water absorption

  29. Wood Destroying Insects • Carpenter ants • Termites • Beetles • Bark/Ambrosia • Metallic wood borers • Long-horned borers • Powderpost beetles

  30. Carpenter Ants • Social insects (Queen/workers) • Use wood for shelter • Forage for food outside nest • Attack softer woods • Colonies <100,000 workers

  31. Carpenter ant Worker

  32. Carpenter ant Frass

  33. Carpenter Ant Damage

  34. Termites • Social Insects • Types • Subterranean • Wet wood • Dry wood • Light colored, small to large insect • Straight antenna • Unrestricted waist • Reproductives have wings of equal length

  35. Dampwood termites • Require very wet wood • Colonies small (several thousand workers) • Confined to Pacific NW and Florida)

  36. Dampwood Termites

  37. Subterranean Termites • Require soil contact • Large colonies (1 to 5 million) • Produce mud-tubes

  38. Subterranean termite Workers

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