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Morrell - Wood Deterioration and its Prevention

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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
Mechanical: impacts, erosion
Sunlight: UV weathering attacks lignin
Biotic Agents

 Fungi
 Insects
 Woodpeckers
 Marine    borers
                     Water


                             Oxygen
                             (air)
Temperature




              Food
Biotic Requirements

   Water  (>20% MC but
    really 30 % or the fsp)
   Moderate Temperature
    (32° to 100°F)
   Oxygen
   Food
     Where is the Water in Wood?


      Occurs in two locations:
      Within cell lumen                 Liquid Free Water
            Liquid
            Called free water              Cell Wall with
                                             Bound Water
      Within the cell wall
            Captured in cell wall matrix
            Called bound water



16                       Wood & Water                        5/15/2011
     Free Water


     Free water is liquid
     water that fills wood’s
     void spaces and affects
     only
         Thermal                    Free Water
          conductivity
         Mass



17                    Wood & Water           5/15/2011
     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.




                    From Haygreen & Bowyer (1989)
18                    Wood & Water                  5/15/2011
     Temperature & Humidity


                    EMC of wood at various
                 temperature and humidity values
                               Relative Humidity %
         Temp. °F
                        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




19                        Wood & Water                      5/15/2011
Bacteria
Remove pit membranes
Degrade extractives
Digest cell walls (Tunneling)
Can be important in
 submerged wood
Fungi
Fungal Spores are Everywhere
Fungal Types
Molds/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 Ants
Social 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
   Subterranean
   Wet   wood
    Dry wood
 Light colored, small to large insect
    Straight antenna
    Unrestricted waist
    Reproductives have wings of equal length
Dampwood termites
Require very wet wood
Colonies small (several
 thousand workers)
Confined to Pacific NW and
 Florida)
Dampwood Termites
Subterranean Termites
Require 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




   http://www.utoronto.ca/forest/termite/micqueen.htm


                                          Termites



                                                             http://www.utoronto.ca/forest/termite/ter
                                                             mite.htm.

 http://www.utoronto.ca/forest/termite/termite.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.ent.orst.edu/urban/Termites.html
http://www.utoronto.ca/forest/termite/ret_dam.htm




 http://www.longpestcontrol.com/termites.html          http://www.longpestcontrol.com/termites.html
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/ins
ect_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/L   http://bioweb.uwlax.edu/zoolab/Table_of_Contents/Lab-05/Ship
ab-05/Shipworms_1/shipworms_1.htm                    worms_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 Protection
Fire 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-Traditional
Modification
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
Reality
Wood has high energy and many
 organisms have evolved to
 utilize it. Unless you deny a
 requirement or alter the
 substrate, something will
 eventually attack.

				
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