Increasing existing concrete slab thickness
Increasing existing concrete slab thickness
(OP)
Is it practical to install a new layer of rebar and increase thickness of a concrete slab for the underside? The rebar at the underside of the existing has corroded and concrete spalled. Also, the top 2" of the 7" slab are to be removed and replaced due to extensive damage (50 year old slab). For these reasons I am wondering if it would be a good idea to reinforce from the bottom. I want to mechanically connect the two pours with SS U pins (see attached) and roughen the existing slab from the bottom and apply some sort of boding agent between the two pours. Does this seem like a practical approach






RE: Increasing existing concrete slab thickness
RE: Increasing existing concrete slab thickness
Also, I would be concerned with what caused the corrosion and spalling in the first place and try to mitigate that prior to any repairs to the slab.
Mike McCann
MMC Engineering
RE: Increasing existing concrete slab thickness
RE: Increasing existing concrete slab thickness
RE: Increasing existing concrete slab thickness
Assuming that the slab is already roughened and jack hammering wouldn't be required, I think placing the concrete would be possible: Traditional formwork, core drill at some spacing (5' oc), at every other core hole build a "hopper" to add a couple feet of pressure head to the fluid concrete and pour concrete until it comes out the next adjacent hole. Use superplasticizers and/or vibrate from below.
I don't think it would be feasible to use a bonding agent because anything out there would cure in the time it takes to build the formwork & pour.
If this slab is below grade - be mindful that if you remove and replace the slab, you're removing a support from the wall that the slab previously provided and significant temporary bracing may be in order.
RE: Increasing existing concrete slab thickness
At 50 years old, I would be worried about possible chloride contamination or other deleterious issues there may be in the existing concrete you propose to leave in place. A new slab, with quality concrete, proper concrete cover and a waterproofing membrane is the way to go.
RE: Increasing existing concrete slab thickness
RE: Increasing existing concrete slab thickness
I agree wih the others, replacing top and bottom slabs wont fix the root cause and will normally cost more money.