Garage Slab Suspended Repair 1

[ENGYYPE]

I am working on repair of a 25+ year old suspended garage floor with advanced cracking in x -y planes as well as significant micro cracks. The cause is advancing corrosion of the internal rebar and wire mesh (builder failed to install 3" grade to door called for in plans to run off of snow / salt melt). The 25' x 27" slab sits on two sheets of corrugated metal. Two 12" I-beams support the load across the free space underneath. The engineer in me says the structure is unsafe in its present condition and would be a home sale deal breaker.

I am contemplating repair options: 1) Install I-beams as cross members as support only, 2) Repair the concrete by injection polyura / epoxy only and, 3) Cut out most of the slab, drill interconnecting rebar into the remaning floor and cast new.

 

[SkiisAndBikes]

ENGYYPE,

How thick is the concrete slab? Typically when rebar corrodes, the primary failure mode is delamination of the concrete. Using injection to repair delaminations would not work. There are many things that should be evaluated before making an informed decision. If the concrete slab has been exposed to chloride's and water for 25+ years, the concrete has likely become chloride contaminated down to the level of the rebar, thus promoting corrosion. Core samples can be taken and analyzed to determine the level of chloride contamination. How much loss of section has occured on the rebar, where exposed, is also important. What is the condition of the corrugated metal pan, is it also corroding? Is the metal pan structural or was the slab designed to span the entire distance and the metal pan only used as formwork.

There are many items that need to be evaluated before making a cost-effective repair decision. I would seek out a local engineer experienced in rehab work who could visit the site and perform an investigation.

 

[ENGYYPE]

Thank you for the info. I must confirm the house plans but I believe the suspended garage floor slab is 6" thick. The corrugated metal sheet underneath appears to be cover. It is corroding badly at the end closest to the garage door above but spots farther back indicates to me seepage through the cracks or/and runner along the corrugation.

Will seek out restoration specialist.

 

[csd72]

From the limited information you have given me, it seems that complete replacement might actually be the cheapest option as well as the best. Once you have removed the slabs you can get a better idea of what the condition of the beam is.