Joint Design Flashcards
Cohesive Failure
Tear down the middle of the joint due to lack of Sealant depth, usually because the backer rod was placed to shallow.
Adhesive failure
Excessive depth of Sealant due to positioning the backer rod too deep
Correct Sealant placement
Depth is 1/2 the size of the width.
What’s the minimum and maximum joint widths for CTS Products?
- no smaller than 1/4”
- no greater than 3/4”
2:1 width to depth ratio
Why are joints designed ?
Joints are designed to ensure sealant movement capability
- Movement allows for changing temperature conditions
What happens to joints in cold temps?
Hot temps?
- Joints treated with sealant will ALWAYS experience compression at low temperatures.
- Low temperatures increase the rigidness of the sealant
- Joints sealed will ALWAYS experience lengthening or extension at high temperatures.
- High temperatures increase the flexibility of the sealant
Explain Cold temperatures and joint placement…
Joint sealants placed at low temperatures will ALWAYS be more rigid during placement.
- Low temperatures lower the viscosity (i.e., increase the stiffness) of the sealant
- Extreme cold will result in rigid material that cannot be placed
Explain Higher temperatures and joint placement…
High temperatures increase the viscosity (i.e., increase the pliability) of the sealant
- Extreme high temperatures will result in very fluid, potentially runny, sealant
- High temperatures increase the viscosity (i.e., increase the pliability) of the sealant
- Extreme high temperatures will result in very fluid, potentially runny, sealant
Define Backer rod
Explain the function of…
Backer Rod is required for proper joint treatment prior to sealant installation.
- Backer Rod is foam material used in both vertical and horizontal joints.
- Its function is
- to prevent three sided bonding within the joint
- allow for adequate movement
- Help ensure proper depth of sealant placement
- The size of the joint will determine the appropriate size of the backer ro
Movement Capability
Aka elongation characteristics
- The elongation characteristics of the material indicate its ability to withstand movement before tearing, de-bonding or cohesive failure (tearing down the middle of the sealant placement).