During new house construction using post-tension slab, a problem has required a hole to be made in the slab.?

Question

The hole is about 2x2 feet and about a foot into the subsoil in order to expose a pipe that needs to be repaired. In the middle of the hole are two intersecting cables (not damaged). After the plumbing repair is completed, how reliable of a concrete repair can be made so as not to effect the integrity of the slab? What questions should I be asking the builder? Should I not be concerned with this situation?

Answer 1

As long as the cables were not damaged, comprised or disturbed the slab repair is relatively easy. Once the pipe repair is completed, back fill with a suitable material and compact it, up to the bottom of the slab.Place a piece of thick plastic between the soil and the slab as a moisture/vapor barrier. Using a 1/2" diameter masonry bit and a hammer drill, drill a series of holes, (two each side of the perimeter of the opening, two inches deep) approximately 8" in from each corner, locating each one in the middle of the slab. Using eight, 4" concrete anchors, set one in each hole. Take a 60 lb. bag of fast setting concrete mix, and prepare as per the instructions. Place the mixed concrete using a shovel or a trowel on the vapor barrier and consolidate it around the anchors. Bring concrete up to the level of the existing slab and smooth out to a level finish. When the concrete sets, it will harden around the anchors there by making it part of the existing slab. I have used this technique on slabs and various size of core holes on bridges.

Answer 2

ALL LOOSE MATERIAL BE REMOVED FROM BREAKING BONDING AGENT APPLIED TO OLD CONCRETE BEFOR POUR ( IT WOULD BE BETTER TO SAW CUT FLAT & DOWELL WITH REBAR ). COMPACT OLD SOIL, COVER W PLASTIC, & RE - POUR! HAPPENS ALL THE TIME, NO CAUSE FOR ALARM. ALSO SEE THAT THE PLASTIC SHEETHING IS STILL IN TACK ON THE CABLES B-4 RE-POUR TO PROTECT THEM FROM CONCRETE!