6" Core Infill of Slab on Metal Deck

[ThStructuresGuy]

I've got a project where they cored four drains in the wrong location and they need to infill. The cores are 6" in diameter and the slab is a 4 1/2" Normal Weight Concrete slab on 2" Composite Deck (6 1/2" Total Thickness) that will receive a 2" topping slab. Has anyone had to do a similar repair before? I was thinking of using a 68 mil sheet attached with screws below the opening and then filling the opening with non-shrink grout.

 

[KootK]

Sounds good. A couple of additional ideas:

- You can get grout that's slightly expansive such that you're kind of keying into the adjacent concrete. Check with Sika.
- Without getting too agressive, perhaps you can bush hammer the perimeter of the opening so that it's a bit conical, expanding upwards.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Agent666]

I assume with the missing decking area that the decking/slab still works and you don't need to augment the slab strength itself, as presumably if the new openings are close by you might have removed twice the area of steel than originally allowed for?

Make sure you get contractor to seal around the edges of your proposed plate using silicon or similar to prevent grout loss (especially if using a pourable grout).

 

[NS4U]

Agree with the expansive grout. Good idea.

I recommend having them drill in some tap cons at an angle around the sides of the cored opening. Use say 3” screws and embed 1.5”. This way they will sort of act like dowels to give you some mechanical fastening.

 

[TehMightyEngineer]

I'd also ensure your contractor properly prepares the existing concrete to not steal moisture from the grout. Leaving the existing concrete dry is not acceptable, they either need to wet the concrete to saturated surface dry or apply a bonding agent.

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

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

 

[XR250]

Are the holes really that much or a problem that you could not just seal the bottom and rod the topping slab into them?