Located where the engineer allows, usually in low-shear zones of beams and slabs, a construction joint is formed against a bulkhead and often carries a keyway, dowels or continuous rebar through it. Where bond matters, the old surface is cleaned of laitance and roughened, often to about 1/4 in amplitude, before new concrete goes against it. In slabs on grade a construction joint usually doubles as a control joint.
Bulkhead the construction joint at the gridline with the dowels through it, we pick up the other half Wednesday.
Also heard as
- CJ
- pour joint
- day joint
Related terms
Cold joint
An unplanned seam left where fresh concrete was placed against concrete that had already begun to set.
Dowel
A smooth steel bar across a slab joint that transfers load while letting the joint open and close.
Laitance
The soft, chalky skin of fines that bleed water leaves on top of concrete, too weak to bond to.
Control joint
A planned groove or sawcut that makes a slab crack in a straight line exactly where the crew wants it.