Degradation of Wood

Question 1

Which are the main degradation mechanisms of wood?

Answer 1

• Hydrometric weathering: breakdown by humidity
• Physical and physico-chemical weathering: porosity related - freezing thaw cycles, crystallization of soluble salts
• Chemical deterioration: UV radiation, selsitive to alkaline and strongly acid environments
• Biological agents: insects, fungi, bacteria

Question 2

Describe the biological agenst

Answer 2

Insects
When humidity is at least 15%
Cause material removal like holes and tunnels

1. Recognition: visual os ultrasound
2. Disinfection: use wood-repellant products
3. Consolidating agents: Natural binding or synthetic binding and fill up the holes

Fungi
Only in absence of oxygen
* Brown rot fungi: degradation of cellulose, cracks of the wood are parallel to the fibers
* Soft rot fungi: Requires high moisture, similar effect as for brown
* White rot fungi: Attacks all components, becomes white and spongey, most dangerous

Bacteria
Can survive in anaerobic environments
Slow action, can induce cracks where other aggressive or biological agents can enter

Question 3

How can we prevent the degradation of wood?

Answer 3

1. Design stage
2. During service
3. Specific prevention:
   * Chemical methods: impregnation to prevent insects or fungi
   * Physical methods: good environmental conditions
   * Biological methods: use other living organisms to kill aggressive organisms
4. A careful design is needed to avoid damages due to moisture