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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 - PowerPoint PPT Presentation
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Wood Deterioration and its Prevention
10 % of all wood cut in the U.S. replaces wood that has failed in service
Wood Losses
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
Biotic Agents
FungiInsectsWoodpeckers Marine borers
Temperature
Food
Water
Oxygen(air)
Biotic Requirements
Water (>20% MC but really 30 % or the fsp)
Moderate Temperature (32° to 100°F)
OxygenFood
Wood & Water16
Occurs in two locations:
Within cell lumen Liquid Called free water
Within the cell wall Captured in cell wall matrix Called bound water
Where is the Water in Wood?
Liquid Free Water
Cell Wall withBound Water
04/20/23
Wood & Water17
Free water is liquid water that fills wood’s void spaces and affects only
Thermal conductivity
Mass
Free Water
Free Water
04/20/23
Wood & Water18
The Equilibrium Moisture Content (EMC) is the MC of wood when it is in equilibrium with the environment’s temperature and humidity.
Equilibrium Moisture Content
From Haygreen & Bowyer (1989)
04/20/23
Wood & Water19
Temp. °FRelative Humidity %
30% 60% 90%
30° 6.3 11.3 21.0
70° 6.2 11.0 20.5
90° 5.9 10.5 19.8
130° 5.2 9.4 18.2
EMC of wood at various temperature and humidity values
Temperature & Humidity
04/20/23
BacteriaRemove pit membranes
Degrade extractives
Digest cell walls (Tunneling)
Can be important in submerged wood
Fungi
Fungal Spores are Everywhere
Fungal TypesMolds/Stain Fungi
Soft rot fungi
Brown rot fungi
White rot fungi
Green Fungal Hyphae in Wood
Blue Stain
http://www.forestry.ubc.ca/brchline/98sept/page4.html
Mold on sapwood
Mold Species
250 to 300,000 species
45 species on Douglas-fir sapwood lumber in the first 6 weeks
Decay Fungus Fruiting Body
Brown Rot
White Rot
Damage by True Dry rot Fungus
Example of Decay Fungus in Culture
Soft Rot on a Utility Pole
Southern pine
Southern pine with soft rot
Soft Rot on a Eucalyptus pole
Decay Effects
Reduced bending strength
Reduced acoustic/insulation value
Increased permeability
Increased water absorption
Wood Destroying Insects
Carpenter ants
Termites
Beetles
Bark/Ambrosia
Metallic wood borers
Long-horned borers
Powderpost beetles
Carpenter AntsSocial insects
(Queen/workers)
Use wood for shelter
Forage for food outside nest
Attack softer woods
Colonies <100,000 workers
Carpenter ant Worker
Carpenter ant Frass
Carpenter Ant Damage
Termites
Social Insects Types
SubterraneanWet woodDry wood
Light colored, small to large insect Straight antenna Unrestricted waistReproductives have wings of equal length
Dampwood termitesRequire very wet wood
Colonies small (several thousand workers)
Confined to Pacific NW and Florida)
Dampwood Termites
Subterranean TermitesRequire soil contact
Large colonies (1 to 5 million)
Produce mud-tubes
Subterranean termite Workers
Termite mud-tube up concrete wall
Wood Deterioration Wood destroying Insects
Termites
http://www.utoronto.ca/forest/termite/termite.htm.
http://www.utoronto.ca/forest/termite/termite.htm
http://www.utoronto.ca/forest/termite/micqueen.htm
Drywood Termites
Attack very dry wood (<13 % MC)
Confined to Pacific SW
Attack wood above ground
Wood Deterioration Wood destroying Insects
Termite Damage
http://www.longpestcontrol.com/termites.html http://www.longpestcontrol.com/termites.html
http://www.ent.orst.edu/urban/Termites.htmlhttp://www.utoronto.ca/forest/termite/ret_dam.htm
Termite vs Carpenter Ant Reproductives
Beetles-Coleoptera
Bark beetles
Ambrosia beetles
Long horned beetles
Metallic wood borers
Powderpost beetles
Wood Deterioration Wood destroying Insects
Ambrosia Beetle
Wood Deterioration Wood destroying Insects
Ambrosia Beetle Damage in a Peeler Core
Beetles-Coleoptera
Golden buprestid Eggs deposited in
green wood Adults leave elliptical
holes when they emerge
Very long life cycle
Buprestid gallery with decay
Beetles-Coleoptera
Long horned Borers
Have long antennae
Larva produce round tunnels
Most have 1-2 year life cycles
Most do not attack finished wood
farm4.static.flickr.com/3113/2847107680_8e229
Powderpost Beetles
Attack dry sapwood Especially destructive to museum pieces or seldom
used furniture Evidenced by fine powder and small emergence holes
http://www.cfr.washington.edu/classes.fm.324/images/insect_galleries/dcp00044.jpg http://www.ces.ncsu.edu/depts/ent/notes/Urban/ppb-wif.htm
Woodpeckers
Excavate galleries to find insects (ants, beetle larvae), create roosts, and nests
Damage opens wood to water, fungi and insects
www.wunderground.com/.../n/NorthLight/284.jpg
Woodpecker Damage
Marine Borers
Require Salt water
Types Shipworms
(Teredo/Bankia)Limnoria (gribbles)Pholads
Shipworms (Teredo) Mollusks Larva borrow into wood leaving only very small entrance hole Filter feed through entrance hole Can reach ¾“ diameter hole that is 1-5 feet long
http://bioweb.uwlax.edu/zoolab/Table_of_Contents/Lab‑05/Shipworms_1/shipworms_1.htm
http://bioweb.uwlax.edu/zoolab/Table_of_Contents/Lab‑05/Shipworms_1/Shipworms_1a/shipworms_1a.htm
Shipworm Head
Internal Shipworm Damage
X-ray of wood showing shipworm tunnels
Pholads
Mollusks ¼“ entrance hole Grows 1-2.5 inch
diameter Weakens pilings
outer shell Tend to be more
tropical
http://membres.lycos.fr/mattauer0001/rivage2.jpg
Pholads
Limnoria (Gribbles)
Small crustacean Live in surface borrows for protection Wave action erodes weakened wood-
producing an hourglass shape Can attack even creosote treated wood
http://www.ffp.csiro.au/wft/wpc/fig1_2.jpg
Limnoria damage at tide line
Preventing Deterioration
Building Issues
-Less air circulation
-Less durable materials
-Changes in design
-HVAC Systems
-Indoor plumbing
Prevention Methods
Keep wood dry
Coat wood
Alter wood/moisture relationships
Poison wood (natural or artificial)
Keep Wood Dry
Avoid soil contact
Long roof overhangs
Gutters
Caulking and paint
Ventilation
Remove vegetation
Durable Heartwoods
Natural Durability
Heartwood only
Varies with age and height
Varies from tree to tree
Second growth can have reduced decay resistance
Artificial ProtectionFire protection
Water repellency
UV protection
Improve physical properties
Improve appearance
Biological protection
Protection Strategies
Create barriers
Chemically alter substrate
Bulk cells to alter wood/moisture relationship
Apply toxins
Wood Orientation
Sapwood is more permeable
Non-TraditionalModification
Thermal Treatment
Bulking (glycol)
Smoking
Silanes
Barrier Treatments
Metal, concrete, plastic , or fiberglass coatings
Paint films
Water repellents
Wood Bulking
Polyethylene glycol
Silanes
Resins/Methacrylates
Waxes
Treat Wood End Tag
Preservatives
Creosote*
Pentachlorophenol*
Inorganic arsenicals*
Copper/organic biocides
Totally carbon based
Goal of Treatment
Create a shell of protection sufficient to support a design load or a barrier that protects the interior
Wood Protection Myths
Charring protects
Salt protects
Silanes protect
Harvesting time matters
Coatings completely protect
RealityWood has high energy and many
organisms have evolved to utilize it. Unless you deny a requirement or alter the substrate, something will eventually attack.