What are the results of high indoor relative humidity?
Possible solutions? - Results:
- Mould growth
- Poor indoor air quality
Solutions:
- Ventilation
- Dehumidification
- Bufering (buffer material taking up water)
What are results of capillary rise?
What are possible solutions - Results:
,- salt efflorescence
- rendering degradation
- poor indoor air quality
Solutions:
- liquid water barrier
- enhanced drying by ventilation
What are results of leakage? - - cracking
- salt efflorescence
Name different degradation mechanisms - Mechanisms:
- physical
- chemical
- biological
--> coupled, interacting
What is one of the main reasons for construction problems related to degradation? -
Moisture
Water triggers physical, chemical and biological processes!
(Estimate: 70% of all problems related to moisture)
When does physical degradation occur? - When the material can no longer sustain the
loads it is exposed to
(Loads due to
- mechanical loading
- hygric loading
- thermal loading
- ...)
Name different types of mechanical sstress that can lead to physical degradation. - -
snow load
- ponding
- moisture load
What is hygric stress? - Material deformation:
- drying shrinkage
- swelling during wetting
--> can cause failure when
- deformation is limited (cracking/ buckling)
- internal stress > material strength
, What are solutions when restrained shrinkage occurs in an outside render? - applied on
wet wall:
-> wait until wall is dry
-> reinforce render
applied on dry wall:
-> reinforce render
What is thermal stress?
Solution? - Material expansion from heat
-> potential buckling/cracking when restrained
Solution: Provide space (tolerance) for expansion
What is crystallization stress? - freeze/thaw (frost) damage
-> liquid water freezes and expands (+9% in volume)
-> stress in limited pore volume
-> material failure if stress > material strength
Describe 3 types of crystallization stress - 1. Frost scaling
- water film on surface
- freezing of film
- ice contracting if cooling continues
- cracking of film --> propagates into material underneath
2. salt weathering
- material with initial cracks wetted with saline water
- water evaporates, salt crystallizes
- crystals expand, crack -> propagates into material
3. salt efflorescence
- crystallinsing not in material, but on surface
- damage mainly aesthetical
Describe 2 types of chemical degradation. - 1. corrosion (of reinforcement)
- rust occupies more volume than iron -> iron expansion in concrete
- induces mechanical stress -> cracking/spalling
2. leaching
- wetting of material with initial cracks /open porosity
- dissultion of minerals in material
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