A4- Sources of Degradation Flashcards
Ageing is the gradual degradation of materials over a long period of time.
This can be accumulated by damage from the ______________ or ____________________.
elements
wear and tear
What material does UV degradation affect?
Polymers.
What is 1 early sign of UV degradation before a material becomes so brittle it cracks:
Discolouration.
What factor accelerates insect attacks, fungal attacks, and lichens/ moss?
High moisture levels.
Lichens and moss __________________ in stonework or brickwork which ______________________. So they are more prone to _________________
retain moisture
prevents evaporation
frost damage
What is the difference between wet rot and dry rot?
Wet rot occurs at a much higher moisture level than dry rot.
To prevent decay in a softwood fence, it can be ___________ to give a ______________________ against fungus and rot.
varnished
protective coating
What is a capillary action?
When _____________ is drawn into ________________.
moisture
narrow gaps
When timber is recently felled, it dries up causing ____________ and _______________.
shrinkage
movement
What does shrinkage cause?
Cracks.
As moisture in timber increases, what decreases?
Strength and stiffness.
Timber must be acclimatised to a site before being cut because kiln-dried timber moved to a __________________ will _____________________. Which will __________ wood fibres and cause ___________ or ________________.
high humidity area
absorb the new moisture
swell
bowing
distortion
What is form of degradation shown in metals?
Oxidation.
