Reinforcement in Concrete Pad

[mweng]

For a concrete pad on grade (e.g., to support a trash dumpster), should reinforcement be at the top or bottom of the slab? My opinion is that reinforcement is at the top to control cracking. Reinforcement is not necessary at the bottom since the bottom of the pad really should not be under any tension (it is supported by subgrade).

 

[Ginger]

If you have a solid, well compacted subgrade, then your assumption is correct. However, if your subgrade is weak and will permit slab flexure, then you will need rebar both top & bottom.

 

[Focht3]

How thick is your pad? Top and bottom reinforcement is only practical (in terms of really getting a RC beam-type action) if the steel reinforcement layers are 200 mm (8 inches) apart, not counting the top and bottom concrete cover. That makes for a nominal overall thickness of 300 mm (12 inches) - which is overkill for most dumpster pads.

Put the steel in the middle. Contractors have enough trouble making sure that it stays there!