Exterior Sealants

8/22/2019 Exterior Sealants

1/20

Exterior Sealants


2/20

Issues

Building Integrity

First line of defense

Prevents serious damage Energy savings


3/20

Failures

Cohesive failures

Adhesive failures


4/20

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


5/20

Dirty joints

Badly designed joints

Wrong primer No primer

Bonding to backer


6/20

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


7/20

Primary Formulation

Polyurethane

Silicone


8/20

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


9/20

Class 100/50 = 100% extension and 50%

compression


10/20

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


11/20

Single component sealant

Rely on ambient moisture to cure

Cure time dependent upon temperature &

relative humidity (unpredictable)

Simple to apply


12/20

Multi Component sealant

Chemically cured

Cure time independent of temperature &

relative humidity (predictable)

Requires experience to mix and apply properly


13/20

Joint Movement

Design to accommodate FULL range of

movement

Full range of temperature (1200F)

Surface temperature

Expansion/ contraction coefficient of materials


14/20

Joint Design

Design and application guidelines

ASTM C1193 Standard guide for use of joint

sealants


15/20

Joint design

Elements: substrate, backer, & sealant

Backer= depth control + bond breaker

Sealant must adhere to substrate (2 sidedadhesion only)

No fillet joints


16/20

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)


17/20

Joint depth

50% joint width

Silicones, maximum joint depth =1/2

Polyurethanes, maximum joint depth =


18/20

Joint width

Function of construction materials and joint

spacing

Silicone seals become more cost effective for

wider joint

ASTM C1193


19/20

Joint with sealant picture


20/20

Reference

Reifsnider, Randal J. Exterior Sealants

ASTM

Expandite joints and sealing manual

Exterior Sealants

Documents

Transcript of Exterior Sealants