Excessively oversized drilled or cored holes for post-installed anchors

[x5bulldog]

I would like to hear what the typical approach/solution is for when construction fouls-up and creates an excessively oversized hole for post-installed anchors. Let's say the hole is oversized by 3 times the anchor diameter or even 4*dia -6*dia.

I am aware Hilti addresses oversized holes for their anchoring adhesive system to some extent. But what about when the hole is slightly more excessive then one would like?

Is an epoxy product usually selected to resolve the issue? Or is this frowned on, due to the high bond strength which would prevent bolt stretch?

I would like to hear what the community has to say. Also, are there good articles that discuss this topic?

Thanks,

 

[TehMightyEngineer]

Entirely depends on the application. High load? Permanent tension? Shear only? Lots of redundancy? Edge distance? How much oversized? etc.

All things equal, I'd probably allow it if it's only slightly oversized. If it was a critical anchor I'd substitute one of the Hilti or Powers epoxies suited for oversized, diamond cored holes. If it was very oversized it might not be easily salvageable.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[Ron]

With this condition, you are outside the tested and published parameters....this creates a standard of care issue for you.

You can core holes of the same size in other areas of the slab and test the anchors. I would suggest using an oven-dried, sand-filled epoxy. Test to failure.

 

[NorthCivil]

sounds like a big boo-boo.

I would contact hilti and get their opinion on going outside of the specs

if its just slightly oversized, i would say compensate by using a larger anchor. i wouldn't fill huge craters with epoxy though.

 

[dik]

You also may want to check with Sika regarding their cementitious patches... They bond very well. if 3 to 4x the anchor rod diameter... this is a huge amount. You may also want to see how highly stressed the rods are and if the loads are transient or full term.

Dik

 

[Yves De Lathouwer]

Following our own experience with our epoxy anchors, We have connected a dubble cylinder anchor made of 40cm of 60mm diameter and 50cm of 35mm diameter in a drilled hole of 80mm diameter.
For the evaluation, we took the data's relative to a rebar of 36mm in a hole of 40mm although it was far to be the case. The pulling test gave us above 60 Tons without pull-out, which was above the requirements of the design.

But one of the issue of making a large hole with epoxy anchor is to keep the screw more or less in the center of the hole. We have used some clamps to keep sure it will stay in the center.

Our chemicals are sold only in Israel but if you want to understand the kind of chemical we used, here is a link to the ESR test of the chemical epoxy we used

https://www.adit.org.il/wp-content/uploads/2018/03/CHEMFIX500-US-Agreement-ESR3853.pdf

Epoxies like Hilti RE500V3, FISCHER FIS EM and similars should give the same result if correctly applied.

Yves De Lathouwer
Head of Engineering Department Adit Ltd

http://www.adit.org.il