Joints in Concrete Construction
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Transcript of Joints in Concrete Construction
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Matt Mettler, P.E.DOWL HKM
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Isolation Joints Construction Joints Contraction Joints Expansion Joints
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Doweled Tied Keyed Tooled Insert (zip strips) Butt Joints
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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
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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
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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
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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
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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
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Slab Slump, 4 to 6 inches SlumpThicknessMCA<3/4" MCA>3/4" < 4"
(in.) (ft.) (ft.) (ft.)5 10 13 156 12 15 187 14 18 218 16 20 249 18 23 2710 20 25 30
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Structure geometry and other elements such as interior walls, columns and piers may dictate layout.
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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.
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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.