hollow core pre tensioned garage slabs

[pyznar]

I ahve a garage in need of restoration - hollow cores show hairline cracking perp. to the strand/core dimesions and in one case the bottom of the slab has delaminated, exposing the strands - what is the best in-situ repair?

 

[JedClampett]

I'd be hesistant to try anything with the in-place panels. Shore up the damaged panels. Get new panels of the same size and replace them. If placing the garage out of service is a problem, do the work over a long weekend.

 

[JAE]

We got into a project once where an old cattle packing plant had hollow core floors that were severely deteriorated. The type of business involved washing down the floors each day and this took a toll on the HC planks.

Delaminated or totally spalled bottoms with strands hanging down. Not sure what was holding up the floor other than grace from above.

The ultimate solution was to install new rebar in the cores, near the bottom, form up the bottom, and fill the cores with concrete/grout to create a mild-reinforced concrete slab. Another solution would be to pair up that with additional steel framing below the HC to cut down the spans.

 

[Ron]

I like JAE's approach. You can also consider shotcrete. Create grid of small reinforcement, use a polymer bonding agent, and shoot it. Make sure the company doing the shotcrete has structural repair experience, not just the local pool builder.