What would be a good thing to use to fill old vent holes in a slab sub-floor?

Question

We are remodling a house built on a slab and we are replacing the furnace and the vents. The old ones where holes in the slab and we would like to fill them before we lay the flooring.

Answer 1

I would use Quickcrete.

Rough the edges 4" down and "paint" with a bit of portland before puring. This will help the new crete to bond.

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