Joint Design

Question 1

Cohesive Failure

Answer 1

Tear down the middle of the joint due to lack of Sealant depth, usually because the backer rod was placed to shallow.

Question 2

Adhesive failure

Answer 2

Excessive depth of Sealant due to positioning the backer rod too deep

Question 3

Correct Sealant placement

Answer 3

Depth is 1/2 the size of the width.

Question 4

What’s the minimum and maximum joint widths for CTS Products?

Answer 4

• no smaller than 1/4”
• no greater than 3/4”

2:1 width to depth ratio

Question 5

Why are joints designed ?

Answer 5

Joints are designed to ensure sealant movement capability

- Movement allows for changing temperature conditions

Question 6

What happens to joints in cold temps?

Hot temps?

Answer 6

• 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

Question 7

Explain Cold temperatures and joint placement…

Answer 7

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

Question 8

Explain Higher temperatures and joint placement…

Answer 8

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

Question 9

Define Backer rod

Explain the function of…

Answer 9

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

Question 10

Movement Capability

Answer 10

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).