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Apartment parking garage floor - to reinforce or not?

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bnickeson

Structural
Apr 7, 2009
74
I am working on a podium-style apartment building with a parking garage on its ground-level floor. It's about a 250'x60' slab-on-grade and is located in an area of the country where de-icing salts and brines are commonly used. My question is, is reinforcing the slab - either with WWF or rebar - a good idea or not? I've only once done an un-reinforced slab-on-grade before for an outdoor covered parking area...is corrosion of the steel reinforcing in the winter a concern at all?

For those who say no to the reinforcing, do you typically thicken your slab a bit and place the control joints tighter than if it were reinforced? Something like a 6" thick slab with joints at 12' o.c.?
 
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In these environs we would typically use a 5" or 6" slab reinforced with about 0.2% reinforcing both ways, 2" from the top and saw cut the 60' width into 4 parts of 15' and would cut the 250' length into panels about 15' or so wide. The kicker is the timing of the sawcutting... this should commence approx 6 or 8 hours after the concrete has set up or earlier with a soff cut saw... as soon as the concrete is hard enough to prevent aggregate ravelling. The slab should be placed on 6" min well compacted granular A material that has no discontinuities in the surface other than for sloping the slab. Good strength (30 or 35 MPa and a low slump 4" or less.

I would not use plain concrete unless the slab were substantially thickened.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik
 
@Dik,

Assuming decent subgrade, what would be the purpose of the reinforcement in a 15x15 square?
 
It just helps with holding things together in the event there is some differential movement. If you can live with the movement, make it an 8" plain concrete slab. [pipe]

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik
 
I'm in the camp of being against any and all unnecessary reinforcing in SOGs. Test the hell out of the compaction effort and let the SOG do its work unreinforced. All reinforcing serves to do in such circumstances is to decrease the lifespan of the SOG and to introduce random cracking that cannot be systematically controlled via saw-cutting.

Dik is correct in that if minor differential is a killer, such as in industrial facilities utilizing forklifts outside that wear away at the joints, then reinforcing is the way to go. But if we are talking about a typical parkade then go slightly thicker, unreinforced, C1-35 mPa concrete, with a proper wet cure + saw cutting, and it'll last longer than nearly anything else around it.

On the other hand, reinforced anything is good for business so either way works for me [tongue]
 
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