Control Joints in Concrete Wall

[davidfi]

I have designed some concrete retaining walls that I am working on developing a control joint detail. Does anyone know of a product like a zip-strip, but for walls? What other products do you use at a control joint in a wall?

Thanks!

 

[msquared48]

I just detail a vertical keyway, cutting the horizontal steel at the joint.

Mike McCann
MMC Engineering

 

[dik]

Use at your own risk...

Dik

 

[rowingengineer]

I have no idea what a zip strip is, does the joint need to be water proof?

Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that them like it

 

[msquared48]

dik:

My only problem with the detail is that the walls could become misaligned at the joint with time without a vertical keyway. Otherwise, to me it is fine.

Mike McCann
MMC Engineering

 

[msquared48]

If the joint is a retaining structure open to the elements, no.

But if it is for a tunnel, building wall or the like, yes.

In otherwords, if you can tolerate the leak, don't put in the specified waterstop. (or clay bentonite panels for that matter - not shown)

Mike McCann
MMC Engineering

 

[JedClampett]

What's your intent? Do you want to structurally isolate adjacent sections? Break up pours?
What's wrong with splicing the reinforcing at the joint and tooling in a notch?

 

[dik]

I have half the rebar going through the joint and it's easy enough to modify it to add a 2x4 keyway. I've also used it with Volclay. I've not had problems with it moving or leaking.

Dik

 

[jike]

I have found that if I run half the bars thru the joint, then a keyway is not necessary. This, however, partially restrains the joint from fully relieving the shrinkage stresses. If all the bars are cut at the joint, then definitely provide a vertical keyway to keep the walls aligned.

I use a (trapezoidal shape) rustication strip (similar to the shapes Greenstreak offers) but normally the contractor elects to cut it from wood). The appearance looks a little more finished plus try to use the same strip at all joints: control, construction and expansion.

If waters weeps thru this joint the bars will rust. If there is the possibility of salt ladden water weeping thru this joint then the bars will corode even faster. This something you might want to consider.

If you want the backside of the wall drained, then provide draintile or weeps thru the wall at the base. If there is finished space on the frontside of the wall, then provide a waterstop in the joint or on the backside. One caution about weeps...if it weeps onto grass OK, but if it weeps onto a walking surface than someone could slip and fall and perhaps you might want to rethink using draintile.

 

[dik]

This was a control joint, not an expansion joint. I use the flat 'waterbar' material on the form because I've had problems with the type that fits in the middle. Walls are 'always' drained with clean stone and I haven't had problems with staining of concrete using the detail.

Dik

 

[jike]

dik is correct! You cannot put a keyway in a control joint unless it is a formed piece of metal that cannot be recovered or reused. Control joint implying that the pour is continuous thru the joint and not stopped at that point.

If all bars are cut in a control joint then you would have to either rely on aggregate interlock of the cracked concrete surface or add greased dowels at the center of the wall to keep the wall sections aligned.