I had opened up five big holes in my concrete slab in various locations to
do drain relocation or repairs. Now I am ready to fill it back up. I got
all the rebars and ties ready. I have already pack the sand back into the
holes up to the bottom of the old slab, soaked the sand thoroughly with
Termidor for termite treatment.

I have also cut a thick viscreen to roughly match the hole size and laid it
down. I am running into two issues.

(1) There are a few places where the copper pipes are coming up to the
manifold, and in that area it's too busy for a viscreen. What should I do
there?

(2) Along the seam where the new viscreen ends and the old viscreen was torn
apart, is there a way to "seal" that off? I asked around and one suggestion
was to use roofing tar...I am not sure of that, another suggestion would be
to spray those expansion foam sealer (like "GREAT STUFF") around the old
concrete edge and new viscreen, as well as all around the copper pipes, then
pour the concrete slab. Would that work? Seems like an interesting idea
but if that stuff expands it would be like concrete sitting on sponge and
when the sponge goes brittle and break off then there is no support, it may
collapse on the pipe?

Any thoughts on the roofing tar or foam idea or any other?

The concrete slab is 4" think and will have rebars tieing the old and new
concrete together.

Thanks,

MC