Suspended Slab Issues

[XR250]

Got a 14 ft. x 16 ft. , 5 inch, plywood formed, exterior suspended slab. The slab is supported around the perimeter on CMU piers approximately 2.5 to 7 ft. O.C. The slab is 35 years old.
The underside of the slab is spalling due to corrosion jacking of the rebar –from decades of rain and deicing salt. The slab is sagging 1 inch in the center. Diagonal cracking exists in the corners of the slab near the cluster of support piers. The rebar appears to be spaced 5-6 inches on center and running in the short direction with about ¾” bottom cover. There is a patio below so the risk of concrete chunks falling on someone’s head is a possibility.
Rather than tear this whole slab out I was thinking of installing two I-beams underneath at third points to significantly cut the span of the concrete. My concern is that further spalling will occur and endanger someone’s life. Does anyone have any ideas on how to catch the debris or prevent further spalling? Chicken wire draped between the beams and perimeter? Frame a ceiling? What other risks exist here that I am overlooking?

Thanks

 

[hokie66]

I wouldn't be encouraging those types of fixes. The slab has reached the end of its life due to neglect.

 

[Tomfh]

I work on a few sites with chicken wire catch nets. It's really crappy. Chunks of concrete hanging in catch nets isn't a good look. Once you start installing protection netting/ceiling it also makes it harder to do any maintenance.

If you intend to keep the slab and people will congregate below then all the loose concrete and bad steel should be removed/cleaned, and the slab profile reinstated.

If there's nothing above the slab it might be better to just replace.

 

[skeletron]

I'll side with the rip and replace team on this one. But for fun, I'll propose a couple left field solutions:

A) Reprofile the bottom of the slab and use some sort of epoxy or cementitious mortar to repair the face prior to installing the new beams.

B) Add FRP wrap

Not sure if those would work. You would need to confirm that the slab is actually designed properly before following through.

 

[XR250]

If there's nothing above the slab it might be better to just replace.

It has a roof above, but could easily be shored for slab replacement.
Sounds like that is the way to go.
Thanks for the help everyone.