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Joints in Concrete Construction

Joints in Concrete Construction. Matt Mettler, P.E. DOWL HKM. Joint Definition. Isolation Joints Construction Joints Contraction Joints Expansion Joints. Joint Construction. Doweled Tied Keyed Tooled Insert (zip strips) Butt Joints. Isolation Joints. Type of control joint

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Joints in Concrete Construction

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  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.

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