Horizontal Joints in Walls

[bigengineer]

At the firm I work for, we have a water treatment facility that has fairly tall walls that hold back water. The walls are 24' tall and 24" thick with heavy reinforcing. The project is in a low seismic zone. The contractor of course wants to pour the walls in two pours, with a horizontal joint/seam in the wall. They are willing to key the joint and use waterstops, but myself and the civil engineer are worried about the increased likelihood for leaks. And I also understand fully the contractor's request. We have never provided walls for this situation this tall and this issue has never came up before. What is standard and does anyone have any advice?

 

[ATSE]

24' can easily be a single pour without a horiz joint.
Does the contractor have a good reason for the request?
Does he have experience with environmental structures?
I don't think there is a code basis for denying the request, but your wall already has a bunch of vertical joints, so extra horizontal joints is not a benefit.
A horiz waterstop (assuming 6" ribbed) in the middle of the wall is a bit of a nuisance for the first pour.

 

[KootK]

There would be a tendency for vertical cracking at the joint as the new concrete shrinks against the restraint of the old. If you decide to let this happen, some additional rebar above the joint might be prudent.


I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[bigengineer]

Thanks for your input guys.

 

[MotorCity]

Horizontal joints are ok if designed and constructed properly, although obviously not preferred. As long as there is a constant supply of concrete being placed, horizontal joints are not necessary. We've had 40' tall, 4' thick walls poured without horizontal joints. For your 24" thick walls, I would require 2 keys and waterstops at the 3rd points in the wall thickness.