Epoxy Rebar in CMU

[mzaitz]

Hello,

I have a project where the Contractor left an opening in the 2 story wall to facilitate moving materials into the building and now needs to close it up. What are the thoughts of drilling up into the bottom of the lintel and epoxying the typical specified reinforcing (#5@16")? This horizontal construction joint occurs right at the top of the windows which is essentially mid-height of the wall (to the second story).

Any thoughts or suggestions?

Thanks,

Mike

 

[phamENG]

Can the shear demand at that point be met by the mortar alone?

Masonry walls tend to have construction joints every 8" or so, and I don't usually worry about it. But at grouted cells I do like to specify a 1" grout key wherever possible. But in this case, since it isn't, I'd check to make sure the wall works without it.

 

[mzaitz]

I am not concern with shear. I am more concerned with proper force transfer with the vertical rebar that is already in the wall and getting a proper lap length for the new epoxied rebar and the existing rebar in the grouted lintel.

 

[phamENG]

I'd say you have very little hope of achieving a good lap. There probably isn't enough room in the cell for the core drill and the rebar that's already there. Best case scenario, you don't damage the bar but the epoxy gets chewed off and you can't get at it to patch it (so then you wasted a lot of money on epoxy rebar).

If you absolutely need continuity (which you may not - look at how they built that opening and see if a simple infill panel will do the job), probably best to knock off face shells, chip out the grout, recoat the bars, and lap in the new ones. Replace the face shells (or just put forms over it if it'll be hidden) and re-grout. Then build the wall grout it and dry pack it. You'd probably need H-blocks or something similar to get them in around the rebar since they won't be able to go over the top.

 

[milkshakelake]

Another way is to put 3" strips of bolted steel plates on the outside, like where your rebar would be, to kind of achieve a splice. Either plates on both sides with thru bolts or plate on one side with epoxied bolts. The bolts will be horizontal but they can still transfer vertical forces. I'd do that in conjunction with the vertical rebar epoxy, not as a replacement. This kind of flies in the face of development length theory, but I've used it with approval from building officials so it can work.

@phamENG You're everywhere these days, trying to become the next KootK?

 

[phamENG]

@phamENG You're everywhere these days, trying to become the next KootK?

Haha - no, I could never aspire to such heights. Just wasting too much time. I'm in the lull that comes from taking time off for the holidays and not writing proposals for most of December. I have 4 months worth of work proposed now, just waiting on approvals...

 

[mzaitz]

All,

To be clear, the rebar in the wall above the opening does not have epoxy on it. I need to drill up into the lintel (from the bottom) that the Contractor put over the construction opening and epoxy the rebar (Hilti 270 I think). The design vertical wall reinforcing is #5@16". I have attached a photo to help clarify the issue.

Thanks,

Mike

 

[milkshakelake]

@mzaitz That's pretty much what I thought. My recommendation applies here.

 

[phamENG]

Oh - got it. I was mixing that up. Thought you were setting epoxy coated rebar in the epoxy. Sorry about that. My other statements still apply. Core drilling into a reinforced and grouted CMU cell without damaging the rebar will be very difficult.