Cracked residential elevated garage slab leading to corrosion

[Jc67roch]

I have client whose elevated, composite deck concrete garage slab is cracked allowing water and salt to begin penetrating to the deck - leading to corrosion. The slab/deck is approximately 20 years old. The design loadings were appropriate (50 psf) and the designer even included a waterproofing membrane (which is apparently failing). Original drawings are attached (cropped border to protect the innocent). Although aged, the client is wondering if it can be saved and/or the life extended. I am thinking that good cleaning, and then coating with epoxy paint will help. Perhaps the epoxy squeegeed into the cracks will seal? Or should we go after all cracks with epoxy injection (more cost but better solution)? The slab does also have control joints, and I am recommending that the caulk here be removed, the joint cleaned, and re-caulked. We do have elevation to install up to a 2" concrete topping also - but I am concerned about additional deadload and cracks simply reflecting thru. Maybe a thinner overlay material? Flexible? Maybe asphalt seal coat and add grit for traction? I also recommended removal of the concrete down to the membrane, replace the membrane but they are really adverse to demolition and reconstruction costs. Does anyone have similar experience and recommendations?

 

[Teguci]

First, if the deck really is composite, then I'd recommend demo. Once the galv on the decking is depleted, the days will be short and the garage will accelerate to the finish line.

Second, if this garage is located in a cold climate region (you did say salt), you will need to check the slab for chloride concentrations. If the top reinforcement is contained within concrete that has a high concentration then you will need to remove and replace that concrete because that reinforcement will continue to rust and fail. For this type of construction in a cold weather area, I suggest full demo as the most appropriate but have a look at hydrodemolition for a fancy option.

Third, the slab should be checked for spalls by sounding. Spalled concrete will need to be removed and replaced so that the rebar is developed into the slab.

Fourth, do a visual on the rest of the structure.

If you've made it to this point, then I think you have a slab that can be rehabilitated. Remove the existing traffic topping system, address the larger cracks as required by the replacement membrane system's documentation and then recoat.

Have your client read the maintenance and repair sections of "Parking Structures" so that he can plan a twice annual washdown schedule and get on a regular repair plan. 20 years is too long to wait for this type of repair.

 

[XR250]

Is there anyway to install a cathodic protection system?
It looks like 4" total thickness concrete on 1 1/2" x 20ga CFD.
I am not sure how he got that to work with the code req'd 2k jack load. I think mine have always been at least 5".