A notched or raised protrusion of concrete located on one face of a construction joint that fits into a recess on the other face is called what?

• A. Dowel
• B. Key
• C. Tongue
• D. Lip

Answer: (B)

A key is a raised projection on one face of a construction joint that fits into a matching recess on the opposite face to create a mechanical interlock. This interlock resists horizontal sliding between successive concrete pours, helping transfer shear across the joint and keep the alignment between pours. The key design roughens the surface so the new concrete can bite into it, improving bond and stiffness at the joint.

This is different from a dowel, which is a steel pin used to transfer load across a joint without providing interlock between the pours. Tongue and lip aren’t standard terms for this concrete-joint feature. So the correct term for a notched or raised protrusion that fits into a recess to interlock the joint is a key.