Epoxy Anchor: Hole size

[Althalus]

We have a retrofit column on a really thick piece of concrete with a WHOLE LOT of rebar. We're limited on space. And the original installers were not that careful about the rebar placement.

1. The contractor told me that as he was drilling into the concrete, the bit got stuck on some rebar. To remove the bit, he has to drill a second hole (much larger) near the original hole.
2. That leaves us with the problem of filling up that larger hole space while still maintaining tension capacity on the anchor into the concrete.
3. Hilti has no guidance on how thick the epoxy can be beyond the minimum. No data.

What considerations are there for filling up a much larger hole with epoxy?
What are alternatives to fill up that space so the anchors can have sufficient capacity?

 

[dik]

Check with the epoxy supplier... many of them only allow a 1/8" hole size difference. You may have to rely on expansive grout of some kind.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[DoubleStud]

I think epoxy is stronger than concrete. If you fill it up full with epoxy, it should be good and you will get the posted capacity from Hilti.

 

[dik]

Different properties... and depending on the epoxy, test results are based on specifics. Some creep... like the Big Dig failure of a few years ago...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[JedClampett]

Hopefully you're using Hilti. Their tech support people get this question all the time. They might even have a position paper on it.

 

[dik]

Hilti is one of the firms that limits the size of their holes...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Althalus]

Thanks for the comments so far.

What kind of grout is used in shear keys? And would it also allow for tension capacity?
What brands of expansive grout do you suggest?

NOTE: This is on a 4' sq pillar foundation. Wrapped in rebar.

 

[Boiler106]

we find that Hilti will often come out to the site to resolve issues like this.

 

[phamENG]

Did you guys read number 3? OP already asked Hilti for help and they have nothing to give them.

It's not going to be popular and will not be cheap, but the answer may be chipping the existing concrete off the rebar, placing cast in bolts with a template, and repouring the pedestal.

 

[GC_Hopi]

Larger bar to match the larger hole size...

Edit: Are you wanting to use the larger second hole or are you just looking to fill it?

 

[WinelandV]

Regarding #3, it's a bit ambiguous if OP just dug through their literature available online/in the manual, if OP called a Hilti distributor, or if OP contacted one of Hilti's field engineers.

Please note that is a "v" (as in Violin) not a "y".

 

[jjl317]

FWIW, I believe that Simpson provides (or at least provided) values for their adhesives in oversized (more than 1/8" larger than the diameter) holes.

 

[phamENG]

How are they going to drill a larger hole without also hitting rebar? Or is this just to go part way down and allow them to knock the original coring bit loose?

 

[Althalus]

It just occurred to me that I wasn't seeing the trees for the forest.

Hilti epoxy is limted to small dimensions for a reason. For larger epoxy fill applications 5-Star comes to the rescue. 5-star is made for larger fill applications.

I had a nice conversation with them. I asked all the questions y'all pointed out. And he had some good answers. So, once it gets too big, the answer is to ditch Hilti and use 5-star.

Thanks for your input. Your comments led me down that line of thinking.

 

[phamENG]

5-Star comes to the rescue

Never heard of them. Can you link to their website?

 

[dik]

and thanks for the info... I'd not heard of 5-Star... and will look into Simpson, too. Thanks...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dik]

another guy (binary term for PC) with the curiosity of a kid.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Eng16080]

Besides manufacturer specific information regarding hole size, the following limitation is also found in the definitions section of ACI 318-14 (annoyingly, it's only in the definitions section and not Chapter 17 where it should be):

anchor, adhesive — a post-installed anchor, inserted into hardened concrete with an anchor hole diameter not greater than 1.5 times the anchor diameter, that transfers loads to the concrete by bond between the anchor and the adhesive, and bond between the adhesive and the concrete.

A few potential solutions:
[ol a]
[li]Use a larger epoxy anchor to work with the larger hole size (as mentioned already). This would seemingly require that the base plate hole is enlarged as well.[/li]
[li]Use another type of post-installed anchor (other than epoxy) that might not have the same hole size limitation. (I don't know if this is possible.)[/li]
[li]Drill new holes in the base plate and concrete, which would hopefully miss the rebar.[/li]
[/ol]

For further brainstorming it would be useful to know overall geometry and load requirements.

 

[Eng16080]

Never heard of 5-star either. Let us know how that works out. Great to learn new things here!

 

[driftLimiter]

HILTI RE500 has documentation and testing for oversized annular gap up to 1.5x the anchor diameter.

There is a reduction in the available bond strength. But to my knowledge its one of the only tested options with oversized holes.

Could also look at core-drilling and using threaded insert anchorage.