The Concrete Network
Wall Joints

Cast concrete retaining walls may be constructed with any or all of the following joints:

Construction Joints: These are vertical or horizontal joints that are used between two successive pours of concrete. Keys are used to increase the shear resistance at the joint. If keys are not used, the surface of the first pour is cleaned and roughened before the next placement of concrete. Keys are almost always formed in the base to give the stem added sliding resistance. The base is formed first, and the stem constructed afterwards.

Contraction Joints: These are vertical joints or grooves formed or cut into the wall that allows the concrete to shrink without noticeable harm. Contraction joints are usually about 0.25 inches wide and about 1/2 to 3/4 inch deep, and are provided at intervals of not exceeding 30 feet.

Expansion Joints: Vertical expansion joints are incorporated into the wall to account for expansion due to temperature changes. These joints may be filled with flexible joint fillers. Greased steel dowels are often cast horizontally into the wall to tie adjacent sections together. Expansion joints should be located at intervals up to 90 feet.