1. Joints in Concrete Construction
Matt Mettler, P.E.
DOWL HKM

2. Joint Definition Isolation Joints Construction Joints
Contraction Joints
Expansion Joints

3. Joint Construction Doweled Tied Keyed Tooled Insert (zip strips)
Butt Joints

4. Isolation Joints Type of control joint
Allows for drying shrinkage and other movements
Provides no vertical or horizontal restraint
May act as an expansion joint if needed

5. Isolation Joint

6. Construction Joints Can be constructed of multiple types of joints:
Doweled
Tied
Keyed
Butt Joint
Are spaced and or located to facilitate construction
Concrete quantity limitation
Sequencing of construction tasks

7. Construction Joint

8. Contraction Joint Also known as control joints
Controls cracking due to drying shrinkage
May be constructed from a variety of methods:
Hand tooled
Saw Cut (my preference)
Inserts

9. Contraction Joints

10. Expansion Joints Used primarily in exterior conditions
Can be doweled but not keyed or tied
Allows for un-restrained movements due to temperature gradients
Can be sealed

11. Expansion Joint

12. Joint Spacing
Function of concrete thickness, coarse aggregate size and concrete slump
PCA recommends the joint spacing be 2 to 3 times (in feet) the concrete thickness (inches)
Example: a 5 inch slab would have joints spaced 10 to 15 feet
It is good practice to maintain a square shape in so much as practical

13. Joint Spacing

14. Joint Spacing
Structure geometry and other elements such as interior walls, columns and piers may dictate layout.

15. Recommendations for Hydraulic Structures
Contraction joints:
Should be doweled or tied
Saw cut floors
Formed with chamfer strips for walls
Try to maintain a square shape between joints
May need waterstop and or joint sealant
Construction joints:
Should be doweled or tied and keyed
Use chamfer strips for adequate consolidation
May need special attention regarding drainage because of hydraulic loading.

16. References
Bureau of Reclamation, “Concrete Manual,” 8th Edition Revised, 1981
Ringo & Anderson, “Designing Floor Slabs on Grade,” 1992
Spears & Panarese, Concrete Floors on Ground, EB075.2D, Portland Cement Association, Skokie, IL, second edition 1983; revised 1990.
Young & Paxson, Undermining of Spillway Chutes, Safety of Dams Conference, Seattle, WA, Fall 2010.