Pouring Slab over precast tank

[bhiggins]

Does anyone see any issues with pouring a concrete slab over a 138"L x 75"W x 59"D precast concrete grease trap tank. The concrete slab is a 7" dumpster pad slab and will be poured directly over the tank. The tank is rated for H20 loads. I'm thinking there should be a crack control joint surrounding the tank at the minimum. Should I detail an expansion joint surrounding the tank with a thickened slab at the edge or is this overkill? I'm thinking there may be some differential settlement of the tank and there should be some detailing to accommodate it, I'm not quite sure what is typical in this situation.

 

[TehMightyEngineer]

Pour away; an H20 grease trap can take way more load than that slab and you'll be helping out the capacity of the tank a lot. I wouldn't even do a crack control joint or a thickened edge; unless they completely botched the install of the tank it shouldn't move deferentially enough to affect a 7" slab.

I did a large precast structure underground with sidewalk pavement directly on top. Regularly sees small plows and the pavement hasn't even cracked after a few years let alone settled.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)