Sawn Expansion Joints in Concrete Retaining Wall 5

[jaengineering]

We have an existing concrete retaining wall ~153' long and 6-9' high. There are no expansion joints in the wall.
Has anyone ever sawn expansion joints into the wall to provide for expansion?

If so, how did that work?
Thank you in advance.

 

[Guastavino]

I haven't into an EXISTING wall, but I imagine you could treat it like a new wall and instead of "forming" in a weakened plane with blocking, you could cut in a v-notch, or even a straight cut and fill it with sealant.

I'd consider things like:

1. Existing rebar locations/cover
2. Age of the wall.
3. Purpose of the wall. What's it retaining?
4. Other things I Can't think of right now.

Point is, whenever you tear down a fence, first determine why it was put there in the first place (to paraphrase GK Chesterton).

 

[JAE]

You could conceivably saw two parallel lines, perhaps 1 to 2 inches apart down the wall. You could get close to, but not perfectly at the top of the footing but that would be OK I think.
Then use a backer rod(s) and sealant.

How old is the concrete?

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[jaengineering]

The wall is less than ~6 months old, and we have been asked to address issue.

Question. What are backer rods? (Never mind)

Thank you for your help!

 

[bridgebuster]

I had a project recently where the contractor saw cut the dummy joints. The saw was mounted on a track attached to the wall. In your case - I believe you want a true expansion joint - follow JAE's advice on the stem. At the footing you could core drill vertically to create the joint through most of the footing. Where the stem and footing overlap you could drill diagonally.

You could wire saw through the whole thing.

 

[hokie66]

Why are you concerned about expansion? The concrete will continue to shrink, for a long time. True, it will tend to change volume with temperature, but thermal expansion would only cause a problem in the case where shrinkage cracks are filled with dirt and debris.

There will be shrinkage cracks in the wall now, running more or less vertical starting at the footing, probably spaced 10 to 15 feet apart. These cracks will not be straight. If your intention is create joints of some width, you need to consider how these relate to the existing shrinkage cracks.

 

[spats]

Hokie is correct. Concrete walls need vertical crack control/contraction joints, and possibly construction joints, but not expansion joints. I normally call for a cast-in V-groove on both sides at 15' maximum on center. In your case, simply add vertical sawcuts deep enough to create a properly weakened plane.

 

[jaengineering]

My personal thanks to everyone who responded to this report. After reviewing your replies and discussing with our local geotechnical/structural engineer, we have decided to cut the control joints every 25'. That will control the cracking locations.