Exterior Sealants
Transcript of Exterior Sealants
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Exterior Sealants
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Issues
Building Integrity
First line of defense
Prevents serious damage Energy savings
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Failures
Cohesive failures
Adhesive failures
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Cohesive failures indicates the sealant could
not resist the stress applied when the
adjacent materials contracted during cold
weather
Adhesive failures occur at the bond line
between sealant and the joint substrate
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Dirty joints
Badly designed joints
Wrong primer No primer
Bonding to backer
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Sealant materials
Exterior sealants are normally an elastomeric
type
Elastomeric sealants means sealants will
withstand joint compression & extension due
to thermal expansion and contraction of the
adjacent materials
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Primary Formulation
Polyurethane
Silicone
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ASTM C920
Rates sealants according to their ability to
withstand movement
% of joint
Example:
Class 25= +/- 25% movement
1 joint w/ class 25 sealant can move from to 1-1/4 in width
Classifies sealant by type, grade, and use
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Class 100/50 = 100% extension and 50%
compression
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Example
Type S single component
Type M multi component
Grade P pourable or self leveling
Grade NS non sag or gun able
Use T Traffic condition Use NT non traffic condition
Use I immersion condition
Use M mortar contact
Use G glass contact Use A aluminum contact
Use O other material contact
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Single component sealant
Rely on ambient moisture to cure
Cure time dependent upon temperature &
relative humidity (unpredictable)
Simple to apply
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Multi Component sealant
Chemically cured
Cure time independent of temperature &
relative humidity (predictable)
Requires experience to mix and apply properly
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Joint Movement
Design to accommodate FULL range of
movement
Full range of temperature (1200F)
Surface temperature
Expansion/ contraction coefficient of materials
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Joint Design
Design and application guidelines
ASTM C1193 Standard guide for use of joint
sealants
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Joint design
Elements: substrate, backer, & sealant
Backer= depth control + bond breaker
Sealant must adhere to substrate (2 sidedadhesion only)
No fillet joints
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Joint design
Substrate must be clean
Silicone sealants require primer on substrate
(except glass surfaces)
Different substrates require different primer
Preconstruction adhesion test (ASTM C794)
Preconstruction stain test (ASTM C150)
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Joint depth
50% joint width
Silicones, maximum joint depth =1/2
Polyurethanes, maximum joint depth =
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Joint width
Function of construction materials and joint
spacing
Silicone seals become more cost effective for
wider joint
ASTM C1193
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Joint with sealant picture
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Reference
Reifsnider, Randal J. Exterior Sealants
ASTM
Expandite joints and sealing manual